LTC1992-2HMS8#TR [ADI]
Operational Amplifier, 1 Func, 4000uV Offset-Max, CMOS, PDSO8;型号: | LTC1992-2HMS8#TR |
厂家: | ADI |
描述: | Operational Amplifier, 1 Func, 4000uV Offset-Max, CMOS, PDSO8 放大器 光电二极管 |
文件: | 总42页 (文件大小:476K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC1992 Family
Low Power, Fully Differential
Input/Output
Amplifier/Driver Family
FEATURES
DESCRIPTION
TheLTC®1992productfamilyconsistsoffivefullydifferen-
tial,lowpoweramplifiers.TheLTC1992isanunconstrained
fully differential amplifier. The LTC1992-1, LTC1992-2,
LTC1992-5 and LTC1992-10 are fixed gain blocks (with
gains of 1, 2, 5 and 10 respectively) featuring precision
on-chip resistors for accurate and ultrastable gain. All of
theLTC1992partshaveaseparateinternalcommonmode
feedback path for outstanding output phase balancing
n
Available with Adjustable Gain or Fixed Gain of 1,
2, 5 or 10
n
0ꢀ.3 ꢁ(axꢂ Gain Error froꢃ ꢄ–0ꢅC to ꢆ5ꢅC
n
.ꢀ5ppꢃ/ꢅC Gain Teꢃperature Coefficient
n
5ppꢃ Gain Long Terꢃ Stability
Fully Differential Input and Output
n
n
C
Stable up to 10,000pF
LOAD
n
n
n
n
n
n
n
Adjustable Output Coꢃꢃon (ode Voltage
Rail-to-Rail Output Swing
and reduced second order harmonics. The V
pin sets
OCM
Low Supply Current: 1mA (Max)
High Output Current: 10mA (Min)
Specified on a Single 2.7V to 5V Supply
DC Offset Voltage <2.5mV (Max)
Available in 8-Lead MSOP Package
the output common mode level independent of the input
common mode level. This feature makes level shifting of
signals easy.
The amplifiers’ differential inputs operate with signals
ranging from rail-to-rail with a common mode level from
the negative supply up to 1.3V from the positive supply.
The differential input DC offset is typically 250μV. The
rail-to-rail outputs sink and source 10mA. The LTC1992
is stable for all capacitive loads up to 10,000pF.
APPLICATIONS
n
Differential Driver/Receiver
n
Differential Amplification
n
Single-Ended to Differential Conversion
Level Shifting
Trimmed Phase Response for Multichannel Systems
The LTC1992 can be used in single supply applications
with supply voltages as low as 2.7V. It can also be used
with dual supplies up to 5V. The LTC1992 is available in
an 8-pin MSOP package.
n
n
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Single-Supply, Single-Ended to Differential Conversion
10k
5V
5V
0V
–5V
5V
3
5V
2.5V
0V
10k
V
4
IN
1
0V
V
+
MID
–
IN
(5V/DIV)
7
V
V
–5V
5V
LTC1992
2
8
+OUT
(2V/DIV)
–OUT
OCM
5V
2.5V
0V
10k
+
–
6
5
0.01μF
OUTPUT SIGNAL
FRO( A
SINGLE-SUPPLꢇ SꢇSTE(
INPUT SIGNAL
FRO( A
5V SꢇSTE(
0V
10k
1992 TA01a
1992 TA01b
1992fb
1
LTC1992 Family
ABSOLUTE MAXIMUM RATINGS
ꢁNote 1ꢂ
Total Supply Voltage (+V to –V ).............................12V
Specified Temperature Range (Note 6)
S
S
Maximum Voltage
on any Pin................ (–V – 0.3V) ≤ V ≤ (+V + 0.3V)
LTC1992CMS8/LTC1992-XCMS8............. 0°C to 70°C
LTC1992IMS8/LTC1992-XIMS8 ...........–40°C to 85°C
LTC1992HMS8/LTC1992-XHMS8 ...... –40°C to 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)...................300°C
S
PIN
S
Output Short-Circuit Duration (Note 3) ............ Indefinite
Operating Temperature Range (Note 5)
LTC1992CMS8/LTC1992-XCMS8/
LTC1992IMS8/LTC1992-XIMS8 ...........–40°C to 85°C
LTC1992HMS8/LTC1992-XHMS8 ...... –40°C to 125°C
PIN CONFIGURATION
LTC1992
LTC1992-X
TOP VIEW
TOP VIEW
–IN 1
8 +IN
7 V
–IN 1
8 +IN
7 V
V
2
3
V
2
3
OCM
S
MID
OCM
S
MID
+
+
–
–
6 –V
6 –V
+V
+V
S
S
+
+
–
–
5 –OUT
5 –OUT
+OUT 4
+OUT 4
MS8 PACKAGE
8-LEAD PLASTIC MSOP
= 150°C, θ = 250°C/W
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T = 150°C, θ = 250°C/W
JMAX
T
JMAX
JA
JA
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART (ARKING*
LTYU
PACKAGE DESCRIPTION
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
SPECIFIED TE(PERATURE RANGE
LTC1992CMS8#PBF
LTC1992IMS8#PBF
LTC1992CMS8#TRPBF
LTC1992IMS8#TRPBF
LTC1992HMS8#TRPBF
LTC1992-1CMS8#TRPBF
LTC1992-1IMS8#TRPBF
LTC1992-1HMS8#TRPBF
LTC1992-2CMS8#TRPBF
LTC1992-2IMS8#TRPBF
LTC1992-2HMS8#TRPBF
LTC1992-5CMS8#TRPBF
LTC1992-5IMS8#TRPBF
LTC1992-5HMS8#TRPBF
LTC1992-10CMS8#TRPBF
LTC1992-10IMS8#TRPBF
LTC1992-10HMS8#TRPBF
0°C to 70°C
LTYU
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
LTC1992HMS8#PBF
LTC1992-1CMS8#PBF
LTC1992-1IMS8#PBF
LTC1992-1HMS8#PBF
LTC1992-2CMS8#PBF
LTC1992-2IMS8#PBF
LTC1992-2HMS8#PBF
LTC1992-5CMS8#PBF
LTC1992-5IMS8#PBF
LTC1992-5HMS8#PBF
LTC1992-10CMS8#PBF
LTC1992-10IMS8#PBF
LTC1992-10HMS8#PBF
LTYU
LTACJ
LTACJ
LTACJ
LTYV
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
LTYV
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
LTYV
LTACK
LTACK
LTACK
LTACL
LTACL
LTACL
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
1992fb
2
LTC1992 Family
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
teꢃperature range, otherwise specifications are at TA = 25ꢅCꢀ +VS = 5V, ꢄVS = 0V, VINC( = VOUTC( = VOC( = 2ꢀ5V, unless otherwise
notedꢀ VOC( is the voltage on the VOC( pinꢀ VOUTC( is defined as ꢁ+VOUT + ꢄVOUTꢂ/2ꢀ VINC( is defined as ꢁ+VIN + ꢄVINꢂ/2ꢀ VINDIFF is
defined as ꢁ+VIN ꢄ ꢄVINꢂꢀ VOUTDIFF is defined as ꢁ+VOUT ꢄ ꢄVOUTꢂꢀ Specifications applicable to all parts in the LTC1992 faꢃilyꢀ
ALL C AND I GRADE
ALL H GRADE
TꢇP
Sꢇ(BOL
PARA(ETER
CONDITIONS
(IN
2.7
TꢇP
(AX
(IN
(AX
UNITS
l
l
V
Supply Voltage Range
Supply Current
11
2.7
11
V
S
I
V = 2.7V to 5V
0.65
0.75
0.7
1.0
1.2
1.2
1.5
0.65
0.8
0.7
0.9
1.0
1.5
1.2
1.8
mA
mA
mA
mA
S
S
V = 5V
S
l
0.8
l
l
l
V
Differential Offset Voltage
(Input Referred) (Note 7)
V = 2.7V
0.25
0.25
0.25
2.5
2.5
2.5
0.25
0.25
0.25
4
4
4
mV
mV
mV
OSDIFF
S
V = 5V
S
V = 5V
S
l
l
l
ΔV /ΔT Differential Offset Voltage Drift
OSDIFF
(Input Referred) (Note 7)
V = 2.7V
10
10
10
10
10
10
μV/°C
μV/°C
μV/°C
S
V = 5V
S
V = 5V
S
l
PSRR
GCM
Power Supply Rejection Ratio
(Input Referred) (Note 7)
V = 2.7V to 5V
75
80
72
80
dB
S
l
l
l
Common Mode Gain(V
/V
)
1
0.1
–85
1
0.1
–85
OUTCM OCM
Common Mode Gain Error
Output Balance (ΔV /(ΔV
0.3
–60
0.35
–60
%
dB
) V = –2V to +2V
OUTDIFF
OUTCM
OUTDIFF
l
l
l
V
Common Mode Offset Voltage
(V – V
V = 2.7V
0.5
1
2
12
15
18
0.5
1
2
15
17
20
mV
mV
mV
OSCM
S
)
V = 5V
OUTCM
OCM
S
V = 5V
S
l
l
l
ΔV
/ΔT Common Mode Offset Voltage Drift
OSCM
V = 2.7V
10
10
10
10
10
10
μV/°C
μV/°C
μV/°C
S
V = 5V
S
V = 5V
S
l
V
Output Signal Common Mode Range
(Voltage Range for the V Pin)
(–V ) + 0.5V
(+V ) – 1.3V (–V ) + 0.5V
(+V ) – 1.3V
V
OUTCMR
S
S
S
S
OCM
l
l
l
R
Input Resistance, V
Pin
500
2
500
2
MΩ
pA
V
INVOCM
OCM
I
Input Bias Current, V
Pin
V = 2.7V to 5V
S
BVOCM
OCM
V
V
Voltage at the V
Pin
2.44
2.50
2.56
2.43
2.50
2.57
MID
OUT
MID
l
l
l
Output Voltage, High
(Note 2)
V = 2.7V, Load = 10k
2.60
2.50
2.29
2.69
2.61
2.52
2.60
2.50
2.29
2.69
2.61
2.52
V
V
V
S
V = 2.7V, Load = 5mA
S
V = 2.7V, Load = 10mA
S
l
l
l
Output Voltage, Low
(Note 2)
V = 2.7V, Load = 10k
0.02
0.10
0.20
0.10
0.25
0.35
0.02
0.10
0.20
0.10
0.25
0.41
V
V
V
S
V = 2.7V, Load = 5mA
S
V = 2.7V, Load = 10mA
S
l
l
l
Output Voltage, High
(Note 2)
V = 5V, Load = 10k
4.90
4.85
4.75
4.99
4.90
4.81
4.90
4.80
4.70
4.99
4.90
4.81
V
V
V
S
V = 5V, Load = 5mA
S
V = 5V, Load = 10mA
S
l
l
l
Output Voltage, Low
(Note 2)
V = 5V, Load = 10k
0.02
0.10
0.20
0.10
0.25
0.35
0.02
0.10
0.20
0.10
0.30
0.42
V
V
V
S
V = 5V, Load = 5mA
S
V = 5V, Load = 10mA
S
l
l
l
Output Voltage, High
(Note 2)
V = 5V, Load = 10k
4.90
4.85
4.65
4.99
4.89
4.80
4.85
4.80
4.60
4.99
4.89
4.80
V
V
V
S
V = 5V, Load = 5mA
S
V = 5V, Load = 10mA
S
l
l
l
Output Voltage, Low
(Note 2)
V = 5V, Load = 10k
–4.99
–4.90
–4.80
–4.90
–4.75
–4.65
–4.98
–4.90
–4.80
–4.85
–4.75
–4.55
V
V
V
S
V = 5V, Load = 5mA
S
V = 5V, Load = 10mA
S
1992fb
3
LTC1992 Family
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
teꢃperature range, otherwise specifications are at TA = 25ꢅCꢀ +VS = 5V, ꢄVS = 0V, VINC( = VOUTC( = VOC( = 2ꢀ5V, unless otherwise
notedꢀ VOC( is the voltage on the VOC( pinꢀ VOUTC( is defined as ꢁ+VOUT + ꢄVOUTꢂ/2ꢀ VINC( is defined as ꢁ+VIN + ꢄVINꢂ/2ꢀ VINDIFF is
defined as ꢁ+VIN ꢄ ꢄVINꢂꢀ VOUTDIFF is defined as ꢁ+VOUT ꢄ ꢄVOUTꢂꢀ Specifications applicable to all parts in the LTC1992 faꢃilyꢀ
ALL C AND I GRADE
ALL H GRADE
TꢇP
Sꢇ(BOL
PARA(ETER
CONDITIONS
(IN
TꢇP
(AX
(IN
(AX
UNITS
l
l
l
I
SC
Output Short-Circuit Current
Sourcing (Notes 2,3)
V = 2.7V, V
=1.35V
20
20
20
30
30
30
20
20
20
30
30
30
mA
mA
mA
S
OUT
V = 5V, V
= 2.5V
S
OUT
V = 5V, V
= 0V
S
OUT
l
l
l
Output Short-Circuit Current Sinking V = 2.7V, V
=1.35V
13
13
13
30
30
30
13
13
13
30
30
30
mA
mA
mA
S
OUT
(Notes 2,3)
V = 5V, V
= 2.5V
S
OUT
V = 5V, V
= 0V
S
OUT
l
A
Large-Signal Voltage Gain
80
80
dB
VOL
The l denotes the specifications which apply over the full operating teꢃperature range, otherwise specifications are at TA = 25ꢅCꢀ
+VS = 5V, ꢄVS = 0V, VINC( = VOUTC( = VOC( = 2ꢀ5V, unless otherwise notedꢀ VOC( is the voltage on the VOC( pinꢀ VOUTC( is defined
as ꢁ+VOUT + ꢄVOUTꢂ/2ꢀ VINC( is defined as ꢁ+VIN + ꢄVINꢂ/2ꢀ VINDIFF is defined as ꢁ+VIN ꢄ ꢄVINꢂꢀ VOUTDIFF is defined as ꢁ+VOUT ꢄ ꢄVOUTꢂꢀ
Specifications applicable to the LTC1992 onlyꢀ
LTC1992C(Sꢆ
LTC1992IS(ꢆ
LTC1992H(Sꢆ
Sꢇ(BOL PARA(ETER
CONDITIONS
V = 2.7V to 5V
(IN
TꢇP
2
(AX
250
100
(IN
TꢇP
2
(AX
400
150
UNITS
pA
l
l
l
l
I
I
Input Bias Current
Input Offset Current
Input Resistance
Input Capacitance
B
S
V = 2.7V to 5V
S
0.1
500
3
0.1
500
3
pA
OS
R
MΩ
pF
IN
IN
C
e
Input Referred Noise Voltage Density f = 1kHz
35
1
35
1
nV/√Hz
fA/√Hz
V
n
i
Input Noise Current Density
f = 1kHz
n
l
l
V
Input Signal Common Mode Range
(–V ) – 0.1V
(+V ) – 1.3V (–V ) – 0.1V
(+V ) – 1.3V
INCMR
S
S
S
S
CMRR
Common Mode Rejection Ratio
(Input Referred)
V
INCM
= –0.1V to 3.7V
69
90
69
90
dB
l
SR
Slew Rate (Note 4)
0.5
1.5
0.5
3.0
1.5
3.2
V/μs
GBW
Gain-Bandwidth Product
T = 25°C
3.0
2.5
1.9
3.2
3.0
3.5
4.0
4.0
3.5
4.0
MHz
MHz
MHz
A
l
l
(f
TEST
= 100kHz)
LTC1992CMS8
LTC1992IMS8/
LTC1992HMS8
1.9
1992fb
4
LTC1992 Family
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
teꢃperature range, otherwise specifications are at TA = 25ꢅCꢀ +VS = 5V, ꢄVS = 0V, VINC( = VOUTC( = VOC( = 2ꢀ5V, unless otherwise
notedꢀ VOC( is the voltage on the VOC( pinꢀ VOUTC( is defined as ꢁ+VOUT + ꢄVOUTꢂ/2ꢀ VINC( is defined as ꢁ+VIN + ꢄVINꢂ/2ꢀ VINDIFF is
defined as ꢁ+VIN ꢄ ꢄVINꢂꢀ VOUTDIFF is defined as ꢁ+VOUT ꢄ ꢄVOUTꢂꢀ Typical values are at TA = 25ꢅCꢀ Specifications apply to the
LTC1992-1 onlyꢀ
LTC1992-1C(Sꢆ
LTC1992-1IS(ꢆ
LTC1992-1H(Sꢆ
Sꢇ(BOL PARA(ETER
CONDITIONS
(IN
TꢇP
(AX
(IN
TꢇP
(AX
UNITS
G
DIFF
Differential Gain
1
1
V/V
%
l
l
Differential Gain Error
0.1
50
3.5
0.3
0.1
50
3.5
0.35
Differential Gain Nonlinearity
Differential Gain Temperature Coefficient
ppm
ppm/°C
e
Input Referred Noise Voltage Density (Note 7) f = 1kHz
Input Resistance, Single-Ended +IN, –IN Pins
45
45
nV/√Hz
kΩ
n
l
R
22.5
30
–0.1V to 4.9V
60
37.5
22
30
–0.1V to 4.9V
60
38
IN
V
Input Signal Common Mode Range
V = 5V
S
V
INCMR
l
l
CMRR
Common Mode Rejection Ratio
(Amplifier Input Referred) (Note 7)
V
= –0.1V to 3.7V
55
55
dB
INCM
SR
Slew Rate (Note 4)
0.5
1.5
3
0.5
1.5
3
V/μs
MHz
GBW
Gain-Bandwidth Product
f
= 180kHz
TEST
The l denotes the specifications which apply over the full operating teꢃperature range, otherwise specifications are at TA = 25ꢅCꢀ
+VS = 5V, ꢄVS = 0V, VINC( = VOUTC( = VOC( = 2ꢀ5V, unless otherwise notedꢀ VOC( is the voltage on the VOC( pinꢀ VOUTC( is defined
as ꢁ+VOUT + ꢄVOUTꢂ/2ꢀ VINC( is defined as ꢁ+VIN + ꢄVINꢂ/2ꢀ VINDIFF is defined as ꢁ+VIN ꢄ ꢄVINꢂꢀ VOUTDIFF is defined as ꢁ+VOUT ꢄ ꢄVOUTꢂꢀ
Typical values are at TA = 25ꢅCꢀ Specifications apply to the LTC1992-2 onlyꢀ
LTC1992-2C(Sꢆ
LTC1992-2IS(ꢆ
LTC1992-2H(Sꢆ
Sꢇ(BOL PARA(ETER
CONDITIONS
(IN
TꢇP
(AX
(IN
TꢇP
(AX
UNITS
G
DIFF
Differential Gain
2
2
V/V
%
l
l
Differential Gain Error
0.1
50
3.5
0.3
0.1
50
3.5
0.35
Differential Gain Nonlinearity
Differential Gain Temperature Coefficient
ppm
ppm/°C
e
Input Referred Noise Voltage Density (Note 7) f = 1kHz
Input Resistance, Single-Ended +IN, –IN Pins
45
45
nV/√Hz
kΩ
n
l
R
22.5
30
–0.1V to 4.9V
60
37.5
22
30
–0.1V to 4.9V
60
38
IN
V
Input Signal Common Mode Range
V = 5V
S
V
INCMR
l
l
CMRR
Common Mode Rejection Ratio
(Amplifier Input Referred) (Note 7)
V
= –0.1V to 3.7V
55
55
dB
INCM
SR
Slew Rate (Note 4)
0.7
2
4
0.7
2
4
V/μs
MHz
GBW
Gain-Bandwidth Product
f
= 180kHz
TEST
1992fb
5
LTC1992 Family
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
teꢃperature range, otherwise specifications are at TA = 25ꢅCꢀ +VS = 5V, ꢄVS = 0V, VINC( = VOUTC( = VOC( = 2ꢀ5V, unless otherwise
notedꢀ VOC( is the voltage on the VOC( pinꢀ VOUTC( is defined as ꢁ+VOUT + ꢄVOUTꢂ/2ꢀ VINC( is defined as ꢁ+VIN + ꢄVINꢂ/2ꢀ VINDIFF is
defined as ꢁ+VIN ꢄ ꢄVINꢂꢀ VOUTDIFF is defined as ꢁ+VOUT ꢄ ꢄVOUTꢂꢀ Typical values are at TA = 25ꢅCꢀ Specifications apply to the
LTC1992-5 onlyꢀ
LTC1992-5C(Sꢆ
LTC1992-5IS(ꢆ
LTC1992-5H(Sꢆ
Sꢇ(BOL PARA(ETER
CONDITIONS
(IN
TꢇP
(AX
(IN
TꢇP
(AX
UNITS
G
DIFF
Differential Gain
5
5
V/V
%
l
l
Differential Gain Error
0.1
50
3.5
0.3
0.1
50
3.5
0.35
Differential Gain Nonlinearity
Differential Gain Temperature Coefficient
ppm
ppm/°C
e
Input Referred Noise Voltage Density (Note 7) f = 1kHz
Input Resistance, Single-Ended +IN, –IN Pins
45
45
nV/√Hz
kΩ
n
l
R
22.5
30
–0.1V to 3.9V
60
37.5
22
30
–0.1V to 3.9V
60
38
IN
V
Input Signal Common Mode Range
V = 5V
S
V
INCMR
l
l
CMRR
Common Mode Rejection Ratio
(Amplifier Input Referred) (Note 7)
V
= –0.1V to 3.7V
55
55
dB
INCM
SR
Slew Rate (Note 4)
0.7
2
4
0.7
2
4
V/μs
MHz
GBW
Gain-Bandwidth Product
f
= 180kHz
TEST
The l denotes the specifications which apply over the full operating teꢃperature range, otherwise specifications are at TA = 25ꢅCꢀ
+VS = 5V, ꢄVS = 0V, VINC( = VOUTC( = VOC( = 2ꢀ5V, unless otherwise notedꢀ VOC( is the voltage on the VOC( pinꢀ VOUTC( is defined
as ꢁ+VOUT + ꢄVOUTꢂ/2ꢀ VINC( is defined as ꢁ+VIN + ꢄVINꢂ/2ꢀ VINDIFF is defined as ꢁ+VIN ꢄ ꢄVINꢂꢀ VOUTDIFF is defined as ꢁ+VOUT ꢄ ꢄVOUTꢂꢀ
Typical values are at TA = 25ꢅCꢀ Specifications apply to the LTC1992-10 onlyꢀ
LTC1992-10C(Sꢆ
LTC1992-10IS(ꢆ
LTC1992-10H(Sꢆ
Sꢇ(BOL PARA(ETER
CONDITIONS
(IN
TꢇP
(AX
(IN
TꢇP
(AX
UNITS
G
Differential Gain
10
0.1
50
10
0.1
50
V/V
%
DIFF
l
l
Differential Gain Error
0.3
0.35
19
Differential Gain Nonlinearity
Differential Gain Temperature Coefficient
ppm
3.5
3.5
ppm/°C
e
n
Input Referred Noise Voltage Density (Note 7) f = 1kHz
Input Resistance, Single-Ended +IN, –IN Pins
45
45
nV/√Hz
kΩ
l
R
11.3
15
–0.1V to 3.8V
60
18.8
11
15
–0.1V to 3.8V
60
IN
V
Input Signal Common Mode Range
V = 5V
V
INCMR
S
l
l
CMRR
Common Mode Rejection Ratio
(Amplifier Input Referred) (Note 7)
V
= –0.1V to 3.7V
55
55
dB
INCM
SR
Slew Rate (Note 4)
0.7
2
4
0.7
2
4
V/μs
MHz
GBW
Gain-Bandwidth Product
f
= 180kHz
TEST
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
LTC1992H/LTC1992-XH are guaranteed functional over the extended
operating temperature of –40°C to 125°C.
Note 6: The LTC1992C/LTC1992-XC are guaranteed to meet the specified
performance limits over the 0°C to 70°C temperature range and are
designed, characterized and expected to meet the specified performance
limits over the –40°C to 85°C temperature range but are not tested or QA
sampled at these temperatures. The LTC1992I/LTC1992-XI are guaranteed
to meet the specified performance limits over the –40°C to 85°C
temperature range. The LTC1992H/LTC1992-XH are guaranteed to meet the
specified performance limits over the –40°C to 125°C temperature range.
Note 7: Differential offset voltage, differential offset voltage drift, CMRR,
noise voltage density and PSRR are referred to the internal amplifier’s
input to allow for direct comparison of gain blocks with discrete amplifiers.
Note 2: Output load is connected to the midpoint of the +V and –V
S
S
potentials. Measurement is taken single-ended, one output loaded at a
time.
Note .: A heat sink may be required to keep the junction temperature
below the absolute maximum when the output is shorted indefinitely.
Note –: Differential output slew rate. Slew rate is measured single ended
and doubled to get the listed numbers.
Note 5: The LTC1992C/LTC1992-XC/LTC1992I/LTC1992-XI are guaranteed
functional over an operating temperature of –40°C to 85°C. The
1992fb
6
LTC1992 Family
Applicable to all parts in the LTC1992 faꢃilyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Offset Voltage
Coꢃꢃon (ode Offset Voltage
Supply Current vs Supply Voltage
vs Teꢃperature ꢁNote 7ꢂ
vs Teꢃperature
0.6
0.4
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
4
V
INCM
V
OCM
= 0V
= 0V
V
INCM
V
OCM
= 0V
= 0V
125°C
85°C
3
2
V
= 5V
S
0.2
25°C
1
V
= 2.5V
S
0
0
–40°C
V
= 1.35V
V
= 1.35V
S
S
–1
–2
–3
–4
–0.2
–0.4
–0.6
–0.8
V
= 2.5V
S
V
= 5V
S
–5
85
TEMPERATURE (°C)
125
–40
25
0
1
2
3
4
5
6
7
8
9
10
–40
25
TEMPERATURE (°C)
125
85
TOTAL SUPPLY VOLTAGE (V)
1992 G02
1992 G01
1992 G03
Coꢃꢃon (ode Offset Voltage
vs VOC( Voltage
Coꢃꢃon (ode Offset Voltage
vs VOC( Voltage
Coꢃꢃon (ode Offset Voltage
vs VOC( Voltage
5
0
5
0
5
0
125°C
125°C
125°C
85°C
25°C
85°C
25°C
85°C
25°C
–40°C
–5
–5
–5
–40°C
–40°C
–10
–15
–20
–10
–15
–20
–10
–15
–20
+V = 2.7V
+V = 5V
+V = 5V
S
S
S
–V = 0V
–V = 0V
–V = –5V
S
S
INCM
S
INCM
V
= 1.35V
V
= 2.5V
V
= 0V
INCM
0
0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
–5 –4 –3 –2 –1
0
1
2
3
4
5
V
VOLTAGE (V)
V
VOLTAGE (V)
V
VOLTAGE (V)
OCM
OCM
OCM
1992 G04
1992 G05
1992 G06
Output Voltage Swing
vs Output Load, VS = 2ꢀ7V
Output Voltage Swing
vs Output Load, VS = 5V
5.00
4.95
4.90
4.85
4.80
4.75
4.70
4.65
4.60
4.55
4.50
1.0
0.9
0.8
0.7
2.70
2.65
2.60
2.55
2.50
2.45
2.40
2.35
2.30
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
125°C
125°C
85°C
25°C
–40°C
25°C
0.6
0.5
0.4
0.3
0.2
0.1
0
85°C
25°C
–40°C
85°C
125°C
25°C
85°C
125°C
–40°C
–40°C
0
5
–20 –15 –10 –5
10 15 20
–20
–5
0
5
10 15 20
–15 –10
LOAD CURRENT (mA)
LOAD CURRENT (mA)
1992 G07
1992 G08
1992fb
7
LTC1992 Family
Applicable to all parts in the LTC1992 faꢃilyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage Swing
VOC( Input Bias Current
vs VOC( Voltage
Differential Input Offset Voltage
vs Tiꢃe ꢁNorꢃalized to t = 0ꢂ
vs Output Load, VS = 5V
10E-9
1E-9
5.0
4.9
4.8
4.7
4.6
4.5
4.4
–3.8
–4.0
–4.2
–4.4
–4.6
–4.8
–5.0
100
TEMP = 35°C
80
60
40
20
0
125°C
–40°C
25°C
100E-12
10E-12
1E-12
85°C
125°C
85°C
25°C
85°C
–20
–40
125°C
–40°C
25°C
–60
–80
+V = 5V
S
–40°C
–V = 0V
S
V
= 2.5V
INCM
100E-15
–100
5
10
–20 –15 –10 –5
0
15 20
800
TIME (HOURS)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0
400
1200
1600
2000
LOAD CURRENT (mA)
V
VOLTAGE (V)
OCM
1992 G09
1992 G10
1992 G11
Differential Gain vs Tiꢃe
ꢁNorꢃalized to t = 0ꢂ
Input Coꢃꢃon (ode Overdrive
Recovery ꢁExpanded Viewꢂ
Input Coꢃꢃon (ode Overdrive
Recovery ꢁDetailed Viewꢂ
10
8
TEMP = 35°C
BOTH INPUTS
(INPUTS TIED TOGETHER)
BOTH INPUTS
(INPUTS TIED
TOGETHER)
6
4
2
OUTPUTS
0
OUTPUTS
–2
–4
–6
–8
–10
+V = 2.5V
+V = 2.5V
S
S
–V = –2.5V
–V = –2.5V
S
S
OCM
V
= 0V
V
= 0V
OCM
LTC1992-10 SHOWN
FOR REFERENCE
LTC1992-10 SHOWN
FOR REFERENCE
1992 G13
1992 G14
800
TIME (HOURS)
0
400
1200
1600
2000
50μs/DIV
1μs/DIV
1992 G12
Output Overdrive Recovery
ꢁExpanded Viewꢂ
Output Overdrive Recovery
ꢁDetailed Viewꢂ
+V = 2.5V, –V = –2.5V, V
= 0V
S
S
OCM
INPUTS
OUTPUTS
INPUTS OUTPUTS
+V = 2.5V
S
–V = –2.5V
S
OCM
V
= 0V
LTC1992-2 SHOWN
FOR REFERENCE
LTC1992-2 SHOWN FOR REFERENCE
50μs/DIV
1992 G15
1992 G16
5μs/DIV
1992fb
8
LTC1992 Family
Applicable to the LTC1992 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Single-Ended Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Differential Phase Response
vs Frequency
12
6
0
12
6
0
0
–20
R
= R = 10k
FB
R
= R = 10k
IN FB
IN
R
= R = 10k
FB
IN
–40
–6
–6
–12
–18
–24
–30
–36
–42
–48
–54
–60
–66
–12
–18
–24
–30
–36
–42
–48
–54
–60
–66
–60
–80
C
=
LOAD
–100
–120
–140
–160
–180
C
C
C
C
C
C
C
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
C
C
C
C
C
C
C
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
10pF
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
50pF
100pF
500pF
1000pF
5000pF
10000pF
= 10pF
= 10pF
10
100
FREQUENCY (kHz)
1000
10
100
1000
10000
10
100
1000
10000
FREQUENCY (kHz)
FREQUENCY (kHz)
1992 G37
1992 G17
1992 G18
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
2.0
1.5
2.0
1.5
2.0
+V = 2.7V
S
+V = 5V
S
+V = 5V
S
–V = 0V
S
–V = –5V
S
–V = 0V
S
1.5
1.0
V
= 1.35V
V
= 0V
OCM
V
= 2.5V
OCM
OCM
1.0
1.0
0.5
0.5
0.5
–40°C
–40°C
–40°C
0
0
0
125°C
125°C
125°C
25°C
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
85°C
25°C
85°C
25°C
85°C
0.6
0
0.3
0.9 1.2 1.5 1.8 2.1 2.4 2.7
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
–5 –4 –3 –2 –1
0
1
2
3
4
5
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
1922 G20
1922 G22
1922 G21
Coꢃꢃon (ode Rejection Ratio
vs Frequency ꢁNote 7ꢂ
Power Supply Rejection Ratio
vs Frequency ꢁNote 7ꢂ
Output Balance vs Frequency
120
100
90
0
–20
ΔV
ΔV
OUTCM
ΔV
ΔV
AMPCM
S
ΔV
ΔV
OUTDIFF
AMPDIFF
AMPDIFF
100
80
80
–V
S
70
+V
S
–40
60
50
60
40
–60
40
30
20
10
0
–80
20
0
–100
100
1k
10k
100k
1M
1
10
100
1k
10k 100k
1M
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
1992 G23
1992 G25
1992 G24
1992fb
9
LTC1992 Family
Applicable to the LTC1992 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Large-Signal
Step Response
Differential Input Large-Signal
Step Response
+V = 2.5V
+V = 2.5V
S
S
–V = –2.5V
–V = –2.5V
S
S
OCM
V
= 0V
V
= 0V
OCM
+V
IN
–V
IN
=
1.5V
1.5V
+V
–V
=
1.5V
1.5V
IN
IN
=
=
C
= 0pF
GAIN = 1
LOAD
GAIN = 1
0V
2.5V
0V
0V
2.5V
0V
C
C
= 10000pF
= 1000pF
LOAD
LOAD
1992 G26
1992 G27
2μs/DIV
20μs/DIV
Single-Ended Input Large-Signal
Step Response
Single-Ended Input Large-Signal
Step Response
+V = 5V
+V = 5V
S
S
–V = 0V
–V = 0V
S
S
OCM
V
= 2.5V
+V = 0V TO 4V
V
= 2.5V
OCM
+V = 0V TO 4V
IN
IN
–V = 2V
–V = 2V
IN
GAIN = 1
IN
C
= 0pF
LOAD
GAIN = 1
C
C
= 10000pF
= 1000pF
LOAD
LOAD
1992 G28
1992 G29
2μs/DIV
20μs/DIV
Differential Input Sꢃall-Signal
Step Response
Differential Input Sꢃall-Signal
Step Response
+V = 2.5V
+V = 2.5V
S
S
–V = –2.5V
–V = –2.5V
S
S
OCM
V
= 0V
V
+V
–V
= 0V
OCM
+V
IN
–V
IN
=
=
50mV
50mV
=
50mV
IN
IN
= 50mV
C
= 0pF
GAIN = 1
LOAD
GAIN = 1
C
C
= 10000pF
= 1000pF
LOAD
LOAD
1992 G30
1992 G31
1μs/DIV
10μs/DIV
1992fb
10
LTC1992 Family
Applicable to the LTC1992 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Single-Ended Input Sꢃall-Signal
Step Response
Single-Ended Input Sꢃall-Signal
Step Response
C
C
= 10000pF
= 1000pF
LOAD
LOAD
2.5V
2.5V
+V = 5V
S
+V = 5V
S
–V = 0V
S
–V = 0V
S
V
= 2.5V
OCM
V
= 2.5V
+V = 0V TO 200mV
IN
OCM
+V = 0V TO 200mV
IN
–V = 100mV
IN
C
–V = 100mV
IN
= 0pF
LOAD
GAIN = 1
GAIN = 1
1992 G32
1992 G33
1μs/DIV
10μs/DIV
THD + Noise vs Frequency
THD + Noise vs Aꢃplitude
–40
–40
–50
–60
–70
–80
–90
–100
500kHz MEASUREMENT BANDWIDTH
500kHz MEASUREMENT BANDWIDTH
+V = 5V
+V = 5V
S
S
–V = –5V
S
–V = –5V
S
–50
–60
V
= 0V
V
= 0V
OCM
OCM
V
= 10V
OUT
P-PDIFF
= 5V
P-PDIFF
50kHz
V
20kHz
OUT
–70
V
V
= 1V
OUT
OUT
P-PDIFF
P-PDIFF
10kHz
5kHz
–80
= 2V
–90
2kHz
1kHz
–100
100
1k
10k
50k
0.1
1
10 20
FREQUENCY (Hz)
INPUT SIGNAL AMPLITUDE (V
)
P-PDIFF
1992 G34
1992 G35
Differential Noise Voltage Density
vs Frequency
VOC( Gain vs Frequency,
VS = 2ꢀ5V
1000
100
10
5
0
C
= 10pF TO 10000pF
LOAD
–5
–10
–15
–20
–25
–30
–35
10
100
1000
10000
10
100
1000
10000
FREQUENCY (Hz)
FREQUENCY (kHz)
1922 G36
1992 G19
1992fb
11
LTC1992 Family
Applicable to the LTC1992-1 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Single-Ended Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Differential Phase Response
vs Frequency
12
6
0
12
6
0
0
–20
–40
–6
–6
–12
–18
–24
–30
–36
–42
–48
–54
–60
–66
–12
–18
–24
–30
–36
–42
–48
–54
–60
–66
–60
–80
C
=
LOAD
–100
–120
–140
–160
–180
C
C
C
C
C
C
C
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
C
LOAD
C
LOAD
C
LOAD
C
LOAD
C
LOAD
C
LOAD
C
LOAD
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
10pF
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
50pF
100pF
500pF
1000pF
5000pF
10000pF
= 10pF
= 10pF
10
100
1000
10
100
1000
10000
10
100
1000
10000
FREQUENCY (kHz)
FREQUENCY (kHz)
FREQUENCY (kHz)
1992 G40
1992 G39
1992 G38
Differential Gain Error
vs Teꢃperature
V
OC( Gain vs Frequency
0.025
0.020
0.015
0.010
0.005
0
5
0
C
= 10pF TO 10000pF
LOAD
–5
–10
–15
–20
–25
–30
–35
–0.005
–0.010
–0.015
–0.020
–0.025
10
100
1000
10000
–50
0
25 50
75 100 125
–25
TEMPERATURE (°C)
FREQUENCY (kHz)
1992 G41
1992 G42
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
5
4
5
4
5
4
+V = 2.7V
S
+V = 5V
S
+V = 5V
S
–V = 0V
S
–V = 0V
S
–V = –5V
S
V
= 1.35V
V
= 2.5V
V
= 0V
OCM
OCM
OCM
3
3
3
2
2
2
1
1
1
125°C
85°C
–40°C
–40°C
0
0
0
125°C
–40°C
125°C
–1
–2
–3
–4
–5
–1
–2
–3
–4
–5
–1
–2
–3
–4
–5
25°C
85°C
25°C
25°C
85°C
0.6
0
0.3
0.9 1.2 1.5 1.8 2.1 2.4 2.7
–3
1.0
–5 –4
–2 –1
0
1
2
3
4
5
0
0.5
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
1922 G43
1922 G45
1922 G44
1992fb
12
LTC1992 Family
Applicable to the LTC1992-1 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Large-Signal
Step Response
Differential Input Large-Signal
Step Response
Coꢃꢃon (ode Rejection Ratio
vs Frequency
100
90
80
70
60
50
40
30
20
10
0
+V = 2.5V
S
–V = –2.5V
S
+V = 2.5V
S
–V = –2.5V
S
V
= 0V
V
+V
–V
= 0V
OCM
OCM
IN
IN
+V
–V
=
1.5V
1.5V
= 0pF
=
1.5V
1.5V
IN
IN
=
=
C
LOAD
0V
0V
C
C
= 10000pF
= 1000pF
LOAD
LOAD
ΔV
AMPCM
ΔV
AMPDIFF
1992 G46
1992 G47
2μs/DIV
20μs/DIV
100
1k
10k
100k
1M
FREQUENCY (Hz)
1992 G48
Single-Ended Input Large-Signal
Step Response
Single-Ended Input Large-Signal
Step Response
Power Supply Rejection Ratio
vs Frequency
100
90
+V = 5V
S
–V = 0V
S
+V = 5V
S
–V = 0V
S
V
= 2.5V
V
= 2.5V
OCM
OCM
IN
IN
80
+V = 0V TO 4V
+V = 0V TO 4V
IN
–V = 2V
C
–V = 2V
IN
70
= 0pF
–V
S
LOAD
60
50
+V
S
2.5V
2.5V
40
30
20
10
0
C
C
= 10000pF
= 1000pF
LOAD
LOAD
ΔV
S
ΔV
AMPDIFF
1992 G49
1992 G50
2μs/DIV
20μs/DIV
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
1992 G51
Differential Input Sꢃall-Signal
Step Response
Differential Input Sꢃall-Signal
Step Response
Output Balance vs Frequency
0
–20
–40
+V = 2.5V
+V = 2.5V
S
–V = –2.5V
S
S
–V = –2.5V
S
OCM
V
= 0V
V
+V
–V
= 0V
OCM
+V
IN
–V
IN
=
50mV
50mV
=
50mV
IN
IN
=
= 50mV
C
= 0pF
LOAD
0V
0V
–60
–80
C
C
= 10000pF
= 1000pF
ΔV
LOAD
LOAD
OUTCM
ΔV
OUTDIFF
–100
1992 G52
1992 G53
1μs/DIV
10μs/DIV
1
10
100
1k
10k 100k
1M
FREQUENCY (Hz)
1992 G54
1992fb
13
LTC1992 Family
Applicable to the LTC1992-1 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Single-Ended Input Sꢃall-Signal
Step Response
Single-Ended Input Sꢃall-Signal
Step Response
Differential Noise Voltage Density
vs Frequency
1000
100
10
C
C
= 10000pF
= 1000pF
LOAD
LOAD
2.5V
2.5V
+V = 5V
S
–V = 0V
S
+V = 5V
S
–V = 0V
S
V
= 2.5V
OCM
V
= 2.5V
+V = 0V TO 200mV
IN
OCM
+V = 0V TO 200mV
IN
–V = 100mV
IN
C
–V = 100mV
IN
= 0pF
LOAD
1992 G56
1992 G55
10μs/DIV
10
100
1000
10000
1μs/DIV
FREQUENCY (Hz)
1922 G57
THD + Noise vs Frequency
THD + Noise vs Aꢃplitude
–40
–40
–50
–60
–70
–80
–90
–100
500kHz MEASUREMENT BANDWIDTH
500kHz MEASUREMENT BANDWIDTH
+V = 5V
+V = 5V
S
S
–V = –5V
S
–V = –5V
S
–50
–60
V
= 0V
V
= 0V
OCM
OCM
V
= 10V
OUT
P-PDIFF
= 5V
P-PDIFF
50kHz
20kHz
V
OUT
–70
V
= 1V
10kHz
5kHz
OUT
P-PDIFF
P-PDIFF
–80
V
= 2V
OUT
–90
2kHz
1kHz
–100
0.1
1
10 20
)
100
1k
10k
50k
INPUT SIGNAL AMPLITUDE (V
FREQUENCY (Hz)
P-PDIFF
1992 G58
1992 G59
1992fb
14
LTC1992 Family
Applicable to the LTC1992-2 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Single-Ended Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Differential Phase Response
vs Frequency
18
12
6
18
12
6
0
–20
0
0
–40
–6
–6
–60
–12
–18
–24
–30
–36
–42
–48
–54
–60
–66
–12
–18
–24
–30
–36
–42
–48
–54
–60
–66
–80
C
=
LOAD
–100
–120
–140
–160
–180
C
C
C
C
C
C
C
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
C
C
C
C
C
C
C
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
10pF
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
50pF
100pF
500pF
1000pF
5000pF
10000pF
= 10pF
= 10pF
10
100
1000
10
100
1000
10000
10
100
1000
10000
FREQUENCY (kHz)
FREQUENCY (kHz)
FREQUENCY (kHz)
1992 G62
1992 G60
1992 G61
Differential Gain Error
vs Teꢃperature
VOC( Gain vs Frequency,
VS = 2ꢀ5V
0.05
0.04
0.03
0.02
0.01
0
5
0
C
= 10pF TO 10000pF
LOAD
–5
–10
–15
–20
–25
–30
–0.01
–0.02
–0.03
–0.04
–0.05
–50
0
25
50
75 100 125
10
100
1000
10000
–25
TEMPERATURE (°C)
FREQUENCY (kHz)
1992 G63
1992 G64
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
(Note 7)
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
(Note 7)
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
(Note 7)
2.0
2.0
1.5
2.0
1.5
+V = 5V
S
+V = 5V
S
+V = 2.7V
S
–V = 0V
S
–V = –5V
S
–V = 0V
S
1.5
1.0
V
= 2.5V
V
= 0V
OCM
V
= 1.35V
OCM
OCM
1.0
1.0
–40°C
25°C
–40°C
25°C
–40°C
25°C
0.5
0.5
0.5
85°C
0
0
0
85°C
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
125°C
125°C
125°C
85°C
1.2 1.5
0
0.3 0.6 0.9
1.8 2.1 2.4 2.7
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
–5 –4 –3 –2 –1
0
1
2
3
4
5
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
1992 G65
1992 G67
1992 G66
1992fb
15
LTC1992 Family
Applicable to the LTC1992-2 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Large-Signal
Step Response
Differential Input Large-Signal
Step Response
Coꢃꢃon (ode Rejection Ratio
vs Frequency (Note 7)
100
90
80
70
60
50
40
30
20
10
0
+V = 2.5V
+V = 2.5V
S
–V = –2.5V
S
S
–V = –2.5V
S
OCM
V
= 0V
V
+V
–V
= 0V
OCM
+V
IN
–V
IN
=
750mV
750mV
=
750mV
IN
IN
=
= 750mV
C
= 0pF
LOAD
0V
0V
2.5V
0V
ΔV
C
C
= 10000pF
= 1000pF
AMPCM
LOAD
LOAD
ΔV
AMPDIFF
1992 G68
1992 G69
2μs/DIV
20μs/DIV
100
1k
10k
100k
1M
FREQUENCY (Hz)
1992 G70
Single-Ended Input Large-Signal
Step Response
Single-Ended Input Large-Signal
Step Response
Power Supply Rejection Ratio
vs Frequency (Note 7)
100
90
+V = 5V
+V = 5V
S
–V = 0V
S
S
–V
+V
S
S
–V = 0V
S
OCM
V
= 2.5V
V
= 2.5V
OCM
80
+V = 0V TO 2V
+V = 0V TO 2V
IN
IN
–V = 1V
–V = 1V
IN
IN
70
C
= 0pF
LOAD
60
50
2.5V
40
30
20
10
0
C
C
= 10000pF
= 1000pF
ΔV
LOAD
LOAD
S
ΔV
AMPDIFF
1992 G71
1992 G72
2μs/DIV
20μs/DIV
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
1992 G73
Differential Input Sꢃall-Signal
Step Response
Differential Input Sꢃall-Signal
Step Response
Output Balance vs Frequency
0
+V = 2.5V
+V = 2.5V
S
–V = –2.5V
S
S
–V = –2.5V
S
OCM
V
= 0V
V
+V
–V
= 0V
OCM
–20
+V
IN
–V
IN
=
25mV
25mV
=
25mV
IN
IN
=
= 25mV
C
= 0pF
LOAD
–40
–60
0V
–80
C
C
= 10000pF
= 1000pF
ΔV
LOAD
LOAD
OUTCM
ΔV
OUTDIFF
–100
1992 G74
1992 G75
2μs/DIV
20μs/DIV
1
10
100
1k
10k 100k
1M
FREQUENCY (Hz)
1992 G76
1992fb
16
LTC1992 Family
Applicable to the LTC1992-2 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Single-Ended Input Sꢃall-Signal
Step Response
Single-Ended Input Sꢃall-Signal
Step Response
Differential Noise Voltage Density
vs Frequency
1000
100
10
C
C
= 10000pF
= 1000pF
LOAD
LOAD
2.5V
2.5V
+V = 5V
S
–V = 0V
S
+V = 5V
S
–V = 0V
S
V
= 2.5V
OCM
V
= 2.5V
+V = 0V TO 100mV
IN
OCM
+V = 0V TO 100mV
IN
–V = 50mV
IN
C
–V = 50mV
IN
= 0pF
LOAD
1992 G77
1992 G78
2μs/DIV
20μs/DIV
10
100
1000
10000
FREQUENCY (Hz)
1922 G79
THD + Noise vs Frequency
THD + Noise vs Aꢃplitude
–40
–40
–50
–60
–70
–80
–90
–100
500kHz MEASUREMENT BANDWIDTH
+V = 5V
S
–V = –5V
S
OCM
–50
–60
V
= 0V
50kHz
20kHz
V
= 1V
OUT
P-PDIFF
–70
10kHz
5kHz
V
= 2V
OUT
P-PDIFF
–80
V
= 5V
P-PDIFF
OUT
2kHz
1kHz
–90
V
= 10V
P-PDIFF
OUT
–100
100
1k
FREQUENCY (Hz)
10k
50k
0.1
1
10
INPUT SIGNAL AMPLITUDE (V
)
P-PDIFF
1992 G81
1992 G80
1992fb
17
LTC1992 Family
Applicable to the LTC1992-5 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Single-Ended Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Differential Phase Response
vs Frequency
30
24
18
30
24
18
0
–20
12
6
12
6
–40
0
0
–60
–6
–6
–80
–12
–18
–24
–30
–36
–42
–48
–54
–60
–12
–18
–24
–30
–36
–42
–48
–54
–60
C
=
10pF
50pF
LOAD
–100
–120
–140
–160
–180
C
C
C
C
C
C
C
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
C
C
C
C
C
C
C
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
100pF
500pF
1000pF
5000pF
10000pF
= 10pF
= 10pF
10
100
1000
10
100
1000
10000
10
100
1000
10000
FREQUENCY (kHz)
FREQUENCY (kHz)
FREQUENCY (kHz)
1992 G82
1992 G84
1992 G83
Differential Gain Error
vs Teꢃperature
VOC( Gain vs Frequency
0.050
0.025
0
5
0
C
= 10pF TO 10000pF
LOAD
–5
–0.025
–0.050
–0.075
–0.100
–0.125
–01.50
–10
–15
–20
–25
–30
10
100
1000
10000
–50
0
25
50
75 100 125
–25
TEMPERATURE (°C)
FREQUENCY (kHz)
1992 G86
1992 G85
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
2.0
1.5
2.0
1.5
2.0
1.5
+V = 5V
S
+V = 2.7V
S
+V = 5V
S
–V = 0V
S
–V = 0V
S
–V = –5V
S
V
= 2.5V
V
= 1.35V
V
= 0V
OCM
OCM
OCM
1.0
1.0
1.0
–40°C
0.5
0.5
0.5
–40°C
–40°C
0
0
0
125°C
85°C
125°C
25°C
25°C
125°C
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
85°C
25°C
85°C
1.0
0
0.5
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
0.6
0
0.3
0.9 1.2 1.5 1.8 2.1 2.4 2.7
–3
–5 –4
–2 –1
0
1
2
3
4
5
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
1922 G88
1922 G87
1922 G89
1992fb
18
LTC1992 Family
Applicable to the LTC1992-5 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Large-Signal
Step Response
Differential Input Large-Signal
Step Response
Coꢃꢃon (ode Rejection Ratio
vs Frequency (Note 7)
100
90
80
70
60
50
40
30
20
10
0
+V = 2.5V
S
–V = –2.5V
S
+V = 2.5V
S
–V = –2.5V
S
V
+V
–V
= 0V
V
= 0V
OCM
IN
IN
OCM
IN
IN
=
300mV
300mV
+V
–V
=
300mV
300mV
= 0pF
=
=
C
LOAD
0V
2.5V
0V
0V
2.5V
0V
C
C
= 10000pF
= 1000pF
ΔV
LOAD
LOAD
AMPCM
ΔV
AMPDIFF
1992 G90
1992 G91
2μs/DIV
20μs/DIV
100
1k
10k
100k
1M
FREQUENCY (Hz)
1992 G92
Single-Ended Input Large-Signal
Step Response
Single-Ended Input Large-Signal
Step Response
Power Supply Rejection Ratio
vs Frequency (Note 7)
100
90
C
C
= 10000pF
= 1000pF
LOAD
LOAD
80
70
+V
S
60
50
–V
S
40
30
20
10
0
+V = 5V
S
–V = 0V
S
+V = 5V
S
–V = 0V
S
V
= 2.5V
OCM
V
= 2.5V
+V = 0V TO 800mV
IN
OCM
ΔV
+V = 0V TO 800mV
IN
S
–V = 400mV
IN
C
ΔV
–V = 400mV
IN
= 0pF
AMPDIFF
LOAD
1992 G93
1992 G94
2μs/DIV
20μs/DIV
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
1992 G95
Differential Input Sꢃall-Signal
Step Response
Differential Input Sꢃall-Signal
Step Response
Output Balance vs Frequency
0
–20
–40
–60
–80
+V = 2.5V
+V = 2.5V
S
–V = –2.5V
S
S
–V = –2.5V
S
OCM
V
= 0V
V
+V
–V
= 0V
OCM
+V
IN
–V
IN
=
10mV
10mV
=
10mV
IN
IN
=
= 10mV
C
= 0pF
LOAD
ΔV
C
C
= 10000pF
= 1000pF
OUTCM
LOAD
LOAD
ΔV
OUTDIFF
–100
1992 G96
1992 G97
5μs/DIV
50μs/DIV
1
10
100
1k
10k 100k
1M
FREQUENCY (Hz)
1992 G98
1992fb
19
LTC1992 Family
Applicable to the LTC1992-5 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Single-Ended Input Sꢃall-Signal
Step Response
Single-Ended Input Sꢃall-Signal
Differential Noise Voltage Density
vs Frequency
Step Response
1000
100
10
C
C
= 10000pF
= 1000pF
LOAD
LOAD
2.5V
2.5V
+V = 5V
S
–V = 0V
S
+V = 5V
S
–V = 0V
S
V
= 2.5V
OCM
V
= 2.5V
+V = 0V TO 40mV
IN
OCM
+V = 0V TO 40mV
IN
–V = 20mV
IN
C
–V = 20mV
IN
= 0pF
LOAD
1992 G99
1992 G100
10
100
1000
10000
5μs/DIV
50μs/DIV
FREQUENCY (Hz)
1922 G101
THD + Noise vs Frequency
THD + Noise vs Aꢃplitude
–40
–40
–50
–60
–70
–80
–90
–100
500kHz MEASUREMENT BANDWIDTH
500kHz MEASUREMENT BANDWIDTH
+V = 5V
+V = 5V
S
S
–V = –5V
S
–50 –V = –5V
S
OCM
V
= 0V
V
= 0V
OCM
50kHz
–60
–70
V
= 1V
= 2V
20kHz
10kHz
OUT
P-PDIFF
V
OUT
P-PDIFF
V
V
= 5V
P-PDIFF
OUT
5kHz
2kHz
–80
= 10V
OUT
P-PDIFF
–90
1kHz
–100
100
1k
FREQUENCY (Hz)
10k
50k
0.1
1
5
INPUT SIGNAL AMPLITUDE (V
)
P-PDIFF
1992 G102
1992 G103
1992fb
20
LTC1992 Family
Applicable to the LTC1992-10 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Single-Ended Input Differential
Gain vs Frequency, VS = 2ꢀ5V
Differential Phase Response
vs Frequency
40
30
40
30
0
–20
20
20
–40
10
10
–60
0
0
–80
–10
–20
–30
–40
–50
–60
–10
–20
–30
–40
–50
–60
C
=
10pF
50pF
100pF
500pF
1000pF
5000pF
10000pF
LOAD
–100
–120
–140
–160
–180
C
C
C
C
C
C
C
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
C
C
C
C
C
C
C
= 10000pF
= 5000pF
= 1000pF
= 500pF
= 100pF
= 50pF
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
LOAD
= 10pF
= 10pF
10
100
1000
10
100
1000
10000
10
100
1000
10000
FREQUENCY (kHz)
FREQUENCY (kHz)
FREQUENCY (kHz)
1992 G106
1992 G104
1992 G105
Differential Gain Error
vs Teꢃperature
V
OC( Gain vs Frequency
0.050
0.025
5
0
C
= 10pF TO 10000pF
LOAD
0
–5
–0.025
–0.050
–0.075
–0.100
–0.125
–0.150
–0.175
–0.200
–10
–15
–20
–25
–30
10
100
1000
10000
–50
0
25 50
75 100 125
–25
TEMPERATURE (°C)
FREQUENCY (kHz)
1992 G108
1992 G107
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
Differential Input Offset Voltage
vs Input Coꢃꢃon (ode Voltage
2.0
1.5
2.0
1.5
2.0
1.5
+V = 2.7V
S
+V = 5V
S
+V = 5V
S
–V = 0V
S
–V = 0V
S
–V = –5V
S
V
= 1.35V
V
= 2.5V
V
= 0V
OCM
OCM
OCM
1.0
1.0
1.0
0.5
0.5
0.5
–40°C
–40°C
–40°C
0
0
0
125°C
125°C
85°C
25°C
125°C
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
25°C
85°C
25°C
85°C
1.0
0
0.5
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
0.6
–3
0
0.3
0.9 1.2 1.5 1.8 2.1 2.4 2.7
–5 –4
–2 –1
0
1
2
3
4
5
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
COMMON MODE VOLTAGE (V)
1922 G111
1922 G110
1922 G109
1992fb
21
LTC1992 Family
Applicable to the LTC1992-10 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Large-Signal
Step Response
Differential Input Large-Signal
Step Response
Coꢃꢃon (ode Rejection Ratio
vs Frequency (Note 7)
100
90
80
70
60
50
40
30
20
10
0
+V = 2.5V
S
–V = –2.5V
S
+V = 2.5V
S
–V = –2.5V
S
V
= 0V
V
+V
–V
= 0V
OCM
IN
IN
OCM
IN
IN
+V
–V
=
150mV
150mV
= 0pF
=
150mV
150mV
=
=
C
LOAD
0V
0V
2.5V
0V
ΔV
C
C
= 10000pF
= 1000pF
AMPCM
LOAD
LOAD
ΔV
AMPDIFF
1992 G112
1992 G113
2μs/DIV
20μs/DIV
100
1k
10k
100k
1M
FREQUENCY (Hz)
1992 G114
Single-Ended Input Large-Signal
Step Response
Single-Ended Input Large-Signal
Step Response
Power Supply Rejection Ratio
vs Frequency (Note 7)
100
90
C
C
= 10000pF
= 1000pF
LOAD
LOAD
80
+V
S
70
–V
S
60
50
2.5V
40
30
20
10
0
+V = 5V
S
–V = 0V
S
OCM
+V = 5V
S
V
= 2.5V
–V = 0V
S
OCM
+V = 0V TO 400mV
IN
V
= 2.5V
–V = 200mV
IN
+V = 0V TO 400mV
IN
ΔV
S
C
= 0pF
LOAD
–V = 200mV
IN
ΔV
AMPDIFF
1992 G115
1992 G116
2μs/DIV
20μs/DIV
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
1992 G117
Differential Input Sꢃall-Signal
Step Response
Differential Input Sꢃall-Signal
Step Response
Output Balance vs Frequency
0
–20
+V = 2.5V
+V = 2.5V
S
–V = –2.5V
S
S
–V = –2.5V
S
OCM
V
= 0V
V
+V
–V
= 0V
OCM
+V
IN
–V
IN
=
5mV
5mV
=
5mV
5mV
IN
IN
=
=
–40
C
= 0pF
LOAD
0V
–60
–80
–100
C
C
= 10000pF
= 1000pF
ΔV
LOAD
LOAD
OUTCM
ΔV
OUTDIFF
–120
1992 G118
1992 G119
10μs/DIV
100μs/DIV
1
10
100
1k
10k 100k
1M
FREQUENCY (Hz)
1992 G120
1992fb
22
LTC1992 Family
Applicable to the LTC1992-10 onlyꢀ
TYPICAL PERFORMANCE CHARACTERISTICS
Single-Ended Input Sꢃall-Signal
Step Response
Single-Ended Input Sꢃall-Signal
Step Response
Differential Noise Voltage Density
vs Frequency
1000
100
10
C
C
= 10000pF
= 1000pF
LOAD
LOAD
2.5V
2.5V
+V = 5V
S
–V = 0V
S
+V = 5V
S
–V = 0V
S
V
= 2.5V
OCM
V
= 2.5V
+V = 0V TO 20mV
IN
OCM
+V = 0V TO 20mV
IN
–V = 10mV
IN
C
–V = 10mV
IN
= 0pF
LOAD
1992 G121
1992 G122
10
100
1000
10000
10μs/DIV
100μs/DIV
FREQUENCY (Hz)
1922 G123
THD + Noise vs Frequency
THD + Noise vs Aꢃplitude
–40
–40
–50
–60
–70
–80
–90
–100
500kHz MEASUREMENT BANDWIDTH
+V = 5V
S
50kHz
20kHz
10kHz
–50 –V = –5V
S
OCM
V
= 0V
–60
–70
V
V
= 1V
= 2V
= 5V
OUT
P-PDIFF
P-PDIFF
P-PDIFF
OUT
V
OUT
5kHz
2kHz
1kHz
–80
–90
–100
100
1k
10k
50k
0.1
1
2
FREQUENCY (Hz)
INPUT SIGNAL AMPLITUDE (V
)
P-PDIFF
1992 G124
1992 G125
1992fb
23
LTC1992 Family
PIN FUNCTIONS
ꢄIN, +IN ꢁPins 1, ꢆꢂ: Inverting and Noninverting Inputs
of the Amplifier. For the LTC1992 part, these pins are
connected directly to the amplifier’s P-channel MOSFET
input devices. The fixed gain LTC1992-X parts have preci-
sion, on-chip gain setting resistors. The input resistors
are nominally 30k for the LTC1992-1, LTC1992-2 and
LTC1992-5 parts. The input resistors are nominally 15k
for the LTC1992-10 part.
+V , ꢄV ꢁPins ., 6ꢂ: The +V and –V power supply pins
S S S S
shouldbebypassedwith0.1μFcapacitorstoanadequateana-
log ground or ground plane. The bypass capacitors should
be located as closely as possible to the supply pins.
+OUT, ꢄOUT ꢁPins –, 5ꢂ: The Positive and Negative
Outputs of the Amplifier. These rail-to-rail outputs are
designed to drive capacitive loads as high as 10,000pF.
V
ꢁPin7ꢂ:Mid-SupplyReference.Thispinisconnected
(ID
V
ꢁPin 2ꢂ: Output Common Mode Voltage Set Pin.
OC(
to an on-chip resistive voltage divider to provide a mid-
supply reference. This provides a convenient way to set
the output common mode level at half-supply. If used for
this purpose, Pin 2 will be shorted to Pin 7, Pin 7 should
be bypassed with a 0.1μF capacitor to ground. If this refer-
ence voltage is not used, leave the pin floating.
The voltage on this pin sets the output signal’s common
mode voltage level. The output common mode level is set
independent of the input common mode level. This is a
high impedance input and must be connected to a known
and controlled voltage. It must never be left floating.
ꢁ1992ꢂ
BLOCK DIAGRAMS
+V
S
3
+V
S
–IN
MID
1
7
2
+
–
V
V
+
+OUT
4
–V
S
200k
200k
+
30k
30k
V
–
+
–
+
A1
A2
V
OCM
+IN
+
+V
–V
–OUT
S
5
1992 BD
–
8
S
6
–V
S
1992fb
24
LTC1992 Family
ꢁ1992-Xꢂ
BLOCK DIAGRAMS
+V
S
3
+V
–V
S
R
R
FB
IN
–IN
1
7
200k
200k
S
4
5
+OUT
–OUT
–
+
+
–
V
MID
+IN
+V
S
R
R
FB
IN
8
PART
R
IN
R
FB
LTC1992-1 30k 30k
LTC1992-2 30k 60k
LTC1992-5 30k 150k
LTC1992-10 15k 150k
–V
S
6
–V
2
1992-X BD
V
S
OCM
APPLICATIONS INFORMATION
Theory of Operation
allows the output signal’s common mode voltage to be
set completely independent of the input signal’s common
mode voltage. Uncoupling the input and output coꢃꢃon
ꢃode voltages ꢃakes signal level shifting easyꢀ
The LTC1992 family consists of five fully differential, low
power amplifiers. The LTC1992 is an unconstrained fully
differentialamplifier.TheLTC1992-1,LTC1992-2,LTC1992-
5 and LTC1992-10 are fixed gain blocks (with gains of
1, 2, 5 and 10 respectively) featuring precision on-chip
resistors for accurate and ultra stable gain.
For a better understanding of the operation of a fully dif-
ferential amplifier, refer to Figure 2. Here, the LTC1992
functional block diagram adds external resistors to real-
ize a basic gain block. Note that the LTC1992 functional
block diagram is not an exact replica of the LTC1992
circuitry. However, the Block Diagram is correct and is
a very good tool for understanding the operation of fully
differential amplifier circuits. Basic op amp fundamentals
together with this block diagram provide all of the tools
neededforunderstandingfullydifferentialamplifiercircuit
applications.
In many ways, a fully differential amplifier functions much
like the familiar, ubiquitous op amp. However, there are
severalkeyareaswherethetwodiffer.ReferringtoFigure 1,
an op amp has a differential input, a high open-loop gain
and utilizes negative feedback (through resistors) to set
the closed-loop gain and thus control the amplifier’s gain
with great precision. A fully differential amplifier has all of
these features plus an additional input and a complemen-
tary output. The complementary output reacts to the input
signal in the same manner as the other output, but in the
opposite direction. Two outputs changing in an equal but
opposite manner require a common reference point (i.e.,
The LTC1992 Block Diagram has two op amps, two sum-
mingblocks(paycloseattentionthesigns)andfourresis-
tors. Two resistors, R
and R
, connect directly to
MID1
MID2
the V
pin and simply provide a convenient mid-supply
MID
opposite relative to what?). The additional input, the V
reference. Its use is optional and it is not involved in the
operationoftheLTC1992’samplifier.TheLTC1992functions
through the use of two servo networks each employing
OCM
input
pin,setsthisreferencepoint.ThevoltageontheV
OCM
directlysetstheoutputsignal’scommonmodevoltageand
1992fb
25
LTC1992 Family
APPLICATIONS INFORMATION
Op Aꢃp
Fully Differential Aꢃplifier
–IN
–IN
+OUT
+
–
–
LTC1992
LTC1992
V
OCM
OUT
A
A
O
O
+IN
+IN
–OUT
+
+
–
• DIFFERENTIAL INPUT
• HIGH OPEN-LOOP GAIN
• SINGLE-ENDED OUTPUT
• DIFFERENTIAL INPUT
• HIGH OPEN-LOOP GAIN
• DIFFERENTIAL OUTPUT
INPUT SETS OUTPUT
OCM
COMMON MODE LEVEL
• V
Op Aꢃp with Negative Feedback
Fully Differential Aꢃplifier with Negative Feedback
R
FB
R
FB
R
R
R
IN
IN
IN
V
–V
+V
+V
V
V
–
+
–
+
IN
IN
IN
OUT
OCM
OCM
+
LTC1992
V
OUT
LTC1992
–
–V
OUT
R
R
FB
GAIN = –
IN
R
R
FB
GAIN = –
V
R
FB
OCM
IN
1992 F01
Figure 1ꢀ Coꢃparison of an Op Aꢃp and a Fully Differential Aꢃplifier
R
FB
+V
S
3
LTC1992
R
IN
INM
–IN
MID
+V
IN
1
7
2
+
S
P
V
+
+OUT
+V
4
R
OUT
MID1
200k
+
R
CMP
30k
V
R
MID2
200k
–
+
–
+
A1
A2
–
R
CMM
30k
V
V
OCM
+IN
+
–OUT
–V
5
OUT
–
S
M
R
IN
INP
–V
IN
8
6
–V
S
R
FB
1992 F02
Figure 2ꢀ LTC1992 Functional Block Diagraꢃ with External Gain Setting Resistors
1992fb
26
LTC1992 Family
APPLICATIONS INFORMATION
negative feedback and using an op amp’s differential input
to create the servo’s summing junction.
the V
voltage. If either of these servos is taken out of
OCM
the specified areas of operation (e.g., inputs taken beyond
thecommonmoderangespecifications,outputshittingthe
supply rails or input signals varying faster than the part
can track), the circuit will not function properly.
One servo controls the signal gain path. The differential
input of op amp A1 creates the summing junction of this
servo.AnyvoltagepresentattheinputofA1isamplified(by
the op amp’s large open-loop gain), sent to the summing
blocksandthenontotheoutputs.Takingnoteofthesignson
thesummingblocks,opampA1’soutputmoves+OUTand
–OUT in opposite directions. Applying a voltage step at
the INM node increases the +OUT voltage while the –OUT
voltage decreases. The RFB resistors connect the outputs
totheappropriateinputsestablishingnegativefeedbackand
closing the servo’s loop. Any servo loop always attempts
to drive its error voltage to zero. In this servo, the error
voltage is the voltage between the INM and INP nodes,
thus A1 will force the voltages on the INP and INM nodes
to be equal (within the part’s DC offset, open loop gain
and bandwidth limits). The “virtual short” between the
two inputs is conceptually the same as that for op amps
and is critical to understanding fully differential amplifier
applications.
Fully Differential Aꢃplifier Signal Conventions
Fully differential amplifiers have a multitude of signals and
signal ranges to consider. To maintain proper operation
with conventional op amps, the op amp’s inputs and its
output must not hit the supply rails and the input signal’s
common mode level must also be within the part’s speci-
fied limits. These considerations also apply to fully dif-
ferential amplifiers, but here there is an additional output
to consider and common mode level shifting complicates
matters. Figure 3 provides a list of the many signals and
specifications as well as the naming convention. The
phrase“commonmode”appearsinmanyplacesandoften
leads to confusion. The fully differential amplifier’s ability
to uncouple input and output common mode levels yields
greatdesignflexibility,butalsocomplicatesmatterssome.
For simplicity, the equations in Figure 3 also assume an
idealamplifierandperfectresistormatching.Foradetailed
analysis,consultthefullydifferentialamplifierapplications
circuit analysis section.
The other servo controls the output common mode level.
The differential input of op amp A2 creates the summing
junction of this servo. Similar to the signal gain servo
above, any voltage present at the input of A2 is amplified,
sent to the summing blocks and then onto the outputs.
However,inthiscase,bothoutputsmoveinthesaꢃedirec-
Basic Applications Circuits
Mostfullydifferentialamplifierapplicationscircuitsemploy
symmetrical feedback networks and are familiar territory
foropampusers. Symmetricalfeedbacknetworksrequire
that the –V /+V
the+V /–V
cally just a standard inverting gain op amp circuit. Figure 4
shows three basic inverting gain op amp circuits and their
correspondingfullydifferentialamplifiercousins.Thevast
majority of fully differential amplifier circuits derive from
old tried and true inverting op amp circuits. To create a
fully differential amplifier circuit from an inverting op amp
circuit,firstsimplytransfertheopamp’sV /V
tothefullydifferentialamplifier’s–V /+V
take a mirror image duplicate of the network and apply it
to the fully differential amplifier’s +V /–V
amp users can comfortably transfer any inverting op amp
circuit to a fully differential amplifier in this manner.
1992fb
tion. The resistors R
and R
connect the +OUT and
CMP
CMM
–OUToutputstoA2’sinvertinginputestablishingnegative
feedback and closing the servo’s loop. The midpoint of
network is a mirror image duplicate of
IN
OUT
OUT
resistors R
and R
derives the output’s common
CMP
CMM
network. Eachofthesehalfcircuitsisbasi-
IN
mode level (i.e., its average). This measure of the output’s
commonmodelevelconnectstoA2’sinvertinginputwhile
A2’s noninverting input connects directly to the V
pin.
OCM
A2 forces the voltages on its inverting and noninverting
inputs to be equal. In other words, it forces the output
common mode voltage to be equal to the voltage on the
V
OCM
input pin.
network
IN OUT
For any fully differential amplifier application to function
properly both the signal gain servo and the common mode
level servo must be satisfied. When analyzing an applica-
tionscircuit,theINPnodevoltagemustequaltheINMnode
voltage and the output common mode voltage must equal
nodes. Then,
IN
OUT
nodes. Op
IN
OUT
27
LTC1992 Family
APPLICATIONS INFORMATION
R
FB
R
R
IN
A
B
INM
INP
2AV
V
2BV
2BV
+
–
–V
+V
OUT
–
P-P
P-P
P-P
IN
IN
–A
A
–B
B
V
V
INDIFF
OUTDIFF
4BV
LTC1992
V
V
V
OCM
OCM
INCM
OUTCM
4AV
P-PDIFF
P-PDIFF
IN
+V
2AV
+
–V
OUT
P-P
–B
–A
R
FB
1992 F03
DIFFERENTIAL
INPUT VOLTAGE
DIFFERENTIAL
OUTPUT VOLTAGE
= V
= +V – –V
IN
= V
OUTDIFF
= +V
– –V
INDIFF
IN
OUT
OUT
+V + –V
IN
+V
OUT
+ –V
2
INPUT COMMON
MODE VOLTAGE
IN
OUTPUT COMMON
MODE VOLTAGE
OUT
= V
=
= V
=
OUTCM
INCM
2
R
R
1
2
FB
IN
+V
–V
=
=
+V – –V
IN
•
•
•
•
+ V
; V
; V
= 0V
= 0V
OUT
OUT
IN
IN
OCM
OCM
OSCM
OSCM
(
(
)
)
R
R
1
2
FB
IN
–V – +V
IN
+ V
R
R
FB
IN
V
V
V
V
= V
INDIFF
•
OUTDIFF
= V – V
INP
AMPDIFF
INM
V
+ V
INM
2
INP
=
AMPCM
OUTCM
= V
OCM
ΔV
AMPCM
CMRR =
; +V = –V
IN
IN
ΔV
AMPDIFF
ΔV
OUTCM
OUTDIFF
OUTPUT BALANCE =
ΔV
R
R
FB
IN
2
2
e
=
+ 1
WHERE: e
= OUTPUT REFERRED NOISE VOLTAGE DENSITY
NOUT
NIN
• √e
+ r
N
NOUT
(
)
NIN
e
= INPUT REFERRED NOISE VOLTAGE DENSITY
R
R
• R
FB
+ R
FB
IN
IN
r
≈ (0.13nV/√Hz)
N
(
)
(RESISTIVE NOISE IS ALREADY INCLUDED IN THE
SPECIFICATIONS FOR THE FIXED GAIN LTC1992-X PARTS)
R
R
FB
IN
V
V
= V
•
+ 1
OSDIFFOUT
OSDIFFIN
(
)
= V
– V
OSCM
OUTCM
OCM
Figure .ꢀ Fully Differential Aꢃplifier Signal Conventions ꢁIdeal Aꢃplifier and Perfect Resistor (atching is Assuꢃedꢂ
Single-Ended to Differential Conversion
input signals. Which input is used for the signal path only
affects the polarity of the differential output signal.
One of the most important applications of fully differential
amplifiersissingle-endedsignalingtodifferentialsignaling
conversion.Manysystemshaveasingle-endedsignalthat
must connect to an ADC with a differential input. The ADC
could be run in a single-ended manner, but performance
usually degrades. Fortunately, all of basic applications
circuits shown in Figure 4, as well as all of the fixed gain
LTC1992-X parts, are equally suitable for both differential
and single-ended input signals. For single-ended input
signals, connect one of the inputs to a reference voltage
(e.g., ground or mid-supply) and connect the other to
the signal path. There are no tradeoffs here as the part’s
performance is the same with single-ended or differential
Signal Level Shifting
Another important application of fully differential ampli-
fier is signal level shifting. Single-ended to differential
conversion accompanied by a signal level shift is very
commonplacewhendrivingADCs.Asnotedinthetheoryof
operation section, fully differential amplifiers have a com-
monmodelevelservothatdeterminestheoutputcommon
mode level independent of the input common mode level.
To set the output common mode level, simply apply the
desired voltage to the V
input pin. The voltage range
OCM
on the V
pin is from (–V + 0.5V) to (+V – 1.3V).
OCM
S S
1992fb
28
LTC1992 Family
APPLICATIONS INFORMATION
Gain Block
R
FB
R
FB
R
IN
R
R
IN
V
IN
–V
+V
+
+V
–V
–
+
–
IN
IN
OUT
OUT
V
OUT
LTC1992
V
OCM
IN
+
–
R
R
FB
R
R
FB
GAIN =
IN
AC Coupled Gain Block
R
FB
FB
C
IN
C
C
IN
R
IN
R
IN
V
IN
–V
IN
+
+V
–V
–
+
–
OUT
OUT
V
LTC1992
V
OUT
OCM
IN
R
IN
+V
IN
+
–
S
H
= H •
O
(S)
S + W
R
FB
P
R
R
1
• C
FB
IN
H
O
=
; W
P
=
R
IN
IN
Single Pole Lowpass Filter
C
C
R
FB
R
FB
R
IN
R
IN
V
IN
–V
IN
+
+V
–V
–
+
–
OUT
OUT
V
LTC1992
V
OUT
OCM
R
IN
+V
IN
+
–
W
S + W
R
FB
P
H
(S)
= H •
O
P
C
R
R
1
FB
FB
IN
WHERE H
=
; W
P
=
O
R
• C
.-Pole Lowpass Filter
R2
C1
R2
C1
R1
R3
R1
R1
R3
C2
R4
R4
V
–V
IN
+
+V
–V
–
+
–
IN
OUT
OUT
R4
C2
C3
2
V
OUT
LTC1992
V
OCM
2
C3
R3
+V
+
–
IN
C1
2
W
S + W
W
O
O
Q
P
H
= H
O
(S)
W
(
)(
1
)
2
2
P
W
S
+ S
+
O
R2
1992 F04
1
R2
R1
WHERE H
=
; W
=
; W =
O
O
P
R4C3
R1 • √R2R3
R1 R2 + R1 R2 + R2 R3
R2R3C1C2
C2
C1
Q =
•
Figure –ꢀ Basic Fully Differential Aꢃplifier Application Circuits ꢁNote: Single-Ended to Differential Conversion is
Easily Accoꢃplished by Connecting One of the Input Nodes, +VIN or ꢄVIN, to a DC Reference Level ꢁeꢀgꢀ, Groundꢂꢂ
1992fb
29
LTC1992 Family
APPLICATIONS INFORMATION
The V
input pin has a very high input impedance and
low frequency CMRR performance. The specifications for
thefixedgainLTC1992-Xpartsincludetheon-chipresistor
matching effects. Also, note that an input common mode
signalappearsasadifferentialoutputsignalreducedbythe
CMRR. As with op amps, at higher frequencies the CMRR
degrades. Refer to the Typical Performance plots for the
details of the CMRR performance over frequency.
OCM
is easily driven by even the weakest of sources. Many
ADCs provide a voltage reference output that defines
either its common mode level or its full-scale level. Apply
the ADC’s reference potential either directly to the V
OCM
pin or through a resistive voltage divider depending on
the reference voltage’s definition. When controlling the
V
OCM
pin by a high impedance source, connect a bypass
At low frequencies, the output balance specification is
capacitor (1000pF to 0.1μF) from the V
pin to ground
OCM
determined by the matching of the on-chip R
CMP
and
CMM
to lower the high frequency impedance and limit external
noise coupling. Other applications will want the output
biased at a midpoint of the power supplies for maximum
output voltage swing. For these applications, the LTC1992
R
resistors. At higher frequencies, the output bal-
ance degrades. Refer to the typical performance plots
for the details of the output balance performance over
frequency.
provides a mid-supply potential at the V
pin. The V
MID
MID
pin connects to a simple resistive voltage divider with
Input Iꢃpedance
two 200k resistors connected between the supply pins.
The input impedance for a fully differential amplifier ap-
plication circuit is similar to that of a standard op amp
inverting amplifier. One major difference is that the input
impedance is different for differential input signals and
single-ended signals. Referring to Figure 3, for differential
input signals the input impedance is expressed by the
following expression:
To use this feature, connect the V
and bypass this node with a capacitor.
pin to the V
pin
MID
OCM
One undesired effect of utilizing the level shifting function
isanincreaseinthedifferentialoutputoffsetvoltagedueto
gainsettingresistormismatch.Theoffsetisapproximately
theamountoflevelshift(V
–V )multipliedbythe
INCM
OUTCM
amount of resistor mismatch. For example, a 2V level shift
with 0.1% resistors will give around 2mV of output offset
(2 • 0.1% = 2mV). The exact amount of offset is dependent
on the application’s gain and the resistor mismatch. For a
detail description, consult the Fully Differential Amplifier
Applications Circuit Analysis section.
R
= 2 • R
IN
INDIFF
Forsingle-endedsignals,theinputimpedanceisexpressed
by the following expression:
RIN
RFB
RINS-E
=
1–
2 • R + R
(
)
C(RR and Output Balance
IN
FB
Onecommonmisconceptionoffullydifferentialamplifiers
isthatthecommonmodelevelservoguaranteesaninfinite
commonmoderejectionratio(CMRR).Thisisnottrue.The
common mode level servo does, however, force the two
outputs to be truly complementary (i.e., exactly opposite
or 180 degrees out of phase). Output balance is a measure
of how complementary the two outputs are.
The input impedance for single-ended signals is slightly
higher than the R value since some of the input signal
IN
is fed back and appears as the amplifier’s input common
mode level. This small amount of positive feedback in-
creases the input impedance.
Driving Capacitive Loads
At low frequencies, CMRR is primarily determined by the
matchingofthegainsettingresistors.Likeanyopamp,the
LTC1992 does not have infinite CMRR, however resistor
mismatching of only 0.018%, halves the circuit’s CMRR.
Standard 1% tolerance resistors yield a CMRR of about
40dB.Formostapplications,resistormatchingdominates
TheLTC1992familyofpartsisstableforallcapacitiveloads
up to at least 10,000pF. While stability is guaranteed, the
part’s performance is not unaffected by capacitive load-
ing. Large capacitive loads increase output step response
ringing and settling time, decrease the bandwidth and
increase the frequency response peaking. Refer to the
1992fb
30
LTC1992 Family
APPLICATIONS INFORMATION
Typical Performance plots for small-signal step response,
large-signal step response and gain over frequency to
appraise the effects of capacitive loading. While the con-
sequences are minor in most instances, consider these
effects when designing application circuits with large
capacitive loads.
random. Once the input returns to the specified input
common mode range, there is a small recovery time then
normal operation proceeds.
)
TheLTC1992’sinputsignalcommonmoderange(V
INCMR
is from (–V – 0.1V) to (+V – 1.3V). This specification
S
S
applies to the voltage at the aꢃplifier’s input, the INP and
INMnodesofFigure2.Thespecificationsforthefixedgain
LTC1992-X parts reflect a higher maximum limit as this
specification is for the entire gain block and references
the signal at the input resistors. Differential input signals
and single-ended signals require a slightly different set
of formulae. Differential signals separate very nicely into
common mode and differential components while single
ended signals do not. Refer to Figure 5 for the formulae
for calculating the available signal range. Additionally,
Table 1 lists some common configurations and their ap-
propriate signal levels.
Input Signal Aꢃplitude Considerations
For application circuits to operate correctly, the amplifier
must be in its linear operating range. To be in the linear
operating range, the input signal’s common mode voltage
mustbewithinthepart’sspecifiedlimitsandtherail-to-rail
outputsmuststaywithinthesupplyvoltagerails.Addition-
ally, the fixed gain LTC1992-X parts have input protection
diodes that limit the input signal to be within the supply
voltage rails. The unconstrained LTC1992 uses external
resistors allowing the source signals to go beyond the
supply voltage rails.
TheLTC1992’soutputsallowrail-to-railsignalswings.The
output voltage on either output is a function of the input
signal’s amplitude, the gain configured and the output
When taken outside of the linear operating range, the
circuit does not perform as expected, however nothing
extreme occurs. Outputs driven into the supply voltage
rails are simply clipped. There is no phase reversal or
oscillation. Once the outputs return to the linear operating
range, there is a small recovery time, then normal opera-
tion proceeds. When the input common mode voltage is
below the specified lower limit, on-chip protection diodes
conduct and clamp the signal. Once the signal returns to
thespecifiedoperatingrange, normaloperationproceeds.
If the input common mode voltage goes slightly above the
specified upper limit (by no more than about 500mV),
the amplifier’s open-loop gain reduces and DC offset and
closed-loop gain errors increase. Return the input back to
thespecifiedrangeandnormalperformancecommences.
If taken well above the upper limit, the amplifier’s input
stage is cut off. The gain servo is now open loop; however,
the common mode servo is still functional. Output bal-
ance is maintained and the outputs go to opposite supply
rails. However, which output goes to which supply rail is
signal’s common mode level set by the V
pin. For
OCM
maximumsignalswing, theV
pinissetatthemidpoint
OCM
of the supply voltages. For other applications, such as an
ADC driver, the required level must fall within the V
OCM
range of (–V + 0.5V) to (+V – 1.3V). For single-ended
S
S
input signals, it is not always obvious which output will
clipfirstthusbothoutputsarecalculatedandtheminimum
value determines the signal limit. Refer to Figure 5 for the
formula and Table 1 for examples.
To ensure proper linear operation both the input common
mode level and the output signal level must be within
the specified limits. These same criteria are also present
with standard op amps. However, with a fully differential
amplifier, it is a bit more complex and old familiar op amp
intuition often leads to the wrong result. This is especially
true for single-ended to differential conversion with level
shifting. The required calculations are a bit tedious, but
are necessary to guarantee proper linear operation.
1992fb
31
LTC1992 Family
APPLICATIONS INFORMATION
Differential Input Signals
R
FB
INM
NODE
R
IN
IN
A
B
2AV
V
2BV
2BV
+
–
–V
+V
+V
OUT
–
P-P
P-P
P-P
IN
–A
A
–B
B
V
V
4BV
INDIFF
OUTDIFF
P-PDIFF
LTC1992
V
V
V
OCM
OCM
INCM
OUTCM
4AV
P-PDIFF
R
2AV
+
–V
IN
P-P
OUT
–B
–A
INP
NODE
R
R
FB
IN
R
G =
FB
INPUT CO((ON (ODE LI(ITS
A. CALCULATE V
MINIMUM AND MAXIMUM GIVEN R , R AND V
IN FB
INCM
OCM
1
V
= (+V – 1.3V) +
(+V – 1.3V – V
S
)
OCM
INCM(MAX)
S
G
1
G
V
= (–V – 0.1V) +
(–V – 0.1V – V
S
)
OCM
INCM(MIN)
S
B. WITH A KNOWN V
, R , R AND V
, CALCULATE COMMON MODE
OCM
OR
INCM IN FB
VOLTAGE AT INP AND INM NODES (V
) AND CHECK THAT IT IS
INCM(AMP)
WITHIN THE SPECIFIED LIMITS.
V
+ V
2
G
G + 1
1
INP
INM
V
=
=
V
+
V
4
INCM(AMP)
INCM
OCM
G + 1
OUTPUT SIGNAL CLIPPING LI(IT
V (V
4
G
) = THE LESSER VALUE OF (+V – V
) OR
(V
– –V )
OCM S
INDIFF(MAX) P-PDIFF
S
OCM
G
Single-Ended Input Signals
R
FB
INM
NODE
R
R
IN
B
2BV
2BV
+
–
V
+V
OUT
–
P-P
P-P
INREF
–B
B
V
4BV
OUTDIFF
P-PDIFF
LTC1992
V
V
V
OCM
OCM
OUTCM
IN
A
V
+
2AV
–V
V
INSIG
P-P
OUT
REF
–B
–A
INP
NODE
R
R
FB
IN
R
G =
FB
INPUT CO((ON (ODE LI(ITS (NOTE: FOR THE FIXED GAIN LTC1992-X PARTS, V
AND V
CANNOT EXCEED THE SUPPLIES)
INREF
INSIG
V
1
G
INREF
2
V
V
V
= 2 +V – 1.3V –
+
+
+V – 1.3V – V
S
INSIG(MAX)
INSIG(MIN)
S
OCM
OCM
ꢁ
ꢂ
ꢂ
ꢁ
ꢁ
ꢂ
ꢂ
V
1
G
INREF
2
= 2 –V – 0.1V –
–V – 0.1V – V
S
S
ꢁ
OR
1
= 2 (+V – –V ) – 1.2V +
(+V – –V ) – 1.2V
INSIGP-P
S
S
S
S
ꢁ
ꢂ
ꢁ
ꢂ
G
OUTPUT SIGNAL CLIPPING LI(IT
2
G
2
G
V
= THE LESSER VALUE OF V
+
(+V – V
) OR V
+
(V
– –V )
OCM S
INSIG(MAX)
INSIG(MIN)
INREF
S
OCM
INREF
2
G
2
V
= THE GREATER VALUE OF V
+
(–V – V
S
) OR V
+
(V
– +V ) 1992 F05
OCM S
INREF
OCM
INREF
G
Figure 5ꢀ Input Signal Liꢃitations
1992fb
32
LTC1992 Family
APPLICATIONS INFORMATION
Table 1ꢀ Input Signal Liꢃitations for Soꢃe Coꢃꢃon Applications
Differential Input Signal, VOC( at (id-Supplyꢀ (VINCM must be within the Min and Max table values and
VINDIFF must be less than the table value)
+V
ꢄV
ꢁVꢂ
GAIN
ꢁV/Vꢂ
V
V
V
V
ꢁV
V
OUTDIFFꢁ(AXꢂ
S
S
OC(
INC(ꢁ(AXꢂ
ꢁVꢂ
INC(ꢁ(INꢂ
ꢁVꢂ
INDIFFꢁ(AXꢂ
ꢁVꢂ
2.7
2.7
2.7
2.7
5
ꢁVꢂ
1.35
1.35
1.35
1.35
2.5
2.5
2.5
2.5
0
ꢂ
ꢁV
ꢂ
P-PDIFF
P-PDIFF
0
1
2
1.450
1.425
1.410
1.405
4.900
4.300
3.940
3.820
7.400
5.550
4.440
4.070
–1.550
–0.825
–0.390
–0.245
–2.700
–1.400
–0.620
–0.360
5.40
5.40
0
2.70
1.08
0.54
5.40
5.40
5.40
0
5
0
10
1
0
10.00
5.00
10.00
10.00
10.00
10.00
20.00
20.00
20.00
20.00
5
0
2
5
0
5
2.00
5
0
10
1
1.00
5
–5
–5
–5
–5
–10.200
–7.650
–6.120
–5.610
20.00
10.00
4.00
5
2
0
5
5
0
5
10
0
2.00
Differential Input Signal, VOC( at Typical ADC Levelsꢀ (VINCM must be within the Min and Max table values and
VINDIFF must be less than the table value)
+V
ꢄV
ꢁVꢂ
GAIN
ꢁV/Vꢂ
V
ꢁVꢂ
V
V
V
ꢁV
V
OUTDIFFꢁ(AXꢂ
S
S
OC(
INC(ꢁ(AXꢂ
ꢁVꢂ
INC(ꢁ(INꢂ
ꢁVꢂ
INDIFFꢁ(AXꢂ
ꢁVꢂ
2.7
2.7
2.7
2.7
5
ꢂ
ꢁV
ꢂ
P-PDIFF
P-PDIFF
0
1
2
1
1.800
1.600
1.480
1.440
5.400
4.550
4.040
3.870
5.400
4.550
4.040
3.870
–1.200
–0.650
–0.320
–0.210
–2.200
–1.150
–0.520
–0.310
4.00
4.00
0
1
2.00
0.80
0.40
8.00
4.00
1.60
0.80
4.00
4.00
4.00
8.00
8.00
8.00
8.00
0
5
1
0
10
1
1
0
2
5
0
2
2
5
0
5
2
5
0
10
1
2
5
–5
–5
–5
–5
2
–12.200
–8.650
–6.520
–5.810
12.00
6.00
2.40
1.20
12.00
12.00
12.00
12.00
5
2
2
5
5
2
5
10
2
1992fb
33
LTC1992 Family
APPLICATIONS INFORMATION
Table 1ꢀ Input Signal Liꢃitations for Soꢃe Coꢃꢃon Applications
(id-Supply Referenced Single-Ended Input Signal, VOC( at (id-Supplyꢀ (The VINSIG Min and Max values listed account for both the input
common mode limits and the output clipping)
+V
ꢄV
GAIN
ꢁV/Vꢂ
V
V
V
V
V
P-P
V
OUTDIFFꢁ(AXꢂ
S
S
OC(
INREF
INSIGꢁ(AXꢂ
INSIGꢁ(INꢂ
INSIGP-Pꢁ(AXꢂ
ꢁVꢂ
2.7
2.7
2.7
2.7
5
ꢁVꢂ
ꢁVꢂ
1.35
1.35
1.35
1.35
2.5
2.5
2.5
2.5
0
ꢁVꢂ
ꢁVꢂ
ꢁVꢂ
ꢁV AROUND V
ꢂ
ꢁV
ꢂ
P-PDIFF
INREF
0
1
2
1.35
1.35
1.35
1.35
2.5
2.5
2.5
2.5
0
1.550
1.500
1.470
1.460
7.300
5.000
3.500
3.000
10.000
5.000
2.000
1.000
–1.350
0.000
0.810
1.080
–2.500
0.000
1.500
2.000
0.40
0.30
0.24
0.22
9.60
5.00
2.00
1.00
20.00
10.00
4.00
2.00
0.40
0
0.60
1.20
2.20
9.60
0
5
0
10
1
0
5
0
2
10.00
10.00
10.00
20.00
20.00
20.00
20.00
5
0
5
5
0
10
1
5
–5
–5
–5
–5
–10.000
–5.000
–2.000
–1.000
5
2
0
0
5
5
0
0
5
10
0
0
(id-Supply Referenced Single-Ended Input Signal, VOC( at Typical ADC Levelsꢀ (The VINSIG Min and Max values listed account for both
the input common mode limits and the output clipping)
+V
ꢄV
GAIN
ꢁV/Vꢂ
V
V
V
V
V
P-P
V
OUTDIFFꢁ(AXꢂ
S
S
OC(
INREF
INSIGꢁ(AXꢂ
INSIGꢁ(INꢂ
INSIGP-Pꢁ(AXꢂ
ꢁVꢂ
2.7
2.7
2.7
2.7
5
ꢁVꢂ
ꢁVꢂ
ꢁVꢂ
ꢁVꢂ
ꢁVꢂ
ꢁV AROUND V
ꢂ
ꢁV
ꢂ
P-PDIFF
INREF
0
1
2
1
1.35
1.35
1.35
1.35
2.5
2.5
2.5
2.5
0
2.250
1.850
1.610
1.530
6.500
4.500
3.300
2.900
6.000
3.000
1.200
0.600
–0.650
0.350
1.80
1.00
0.52
0.36
8.00
4.00
1.60
0.80
12.00
6.00
2.40
1.20
1.80
0
1
2.00
2.60
3.60
8.00
8.00
8.00
8.00
0
5
1
0.950
0
10
1
1
1.150
0
2
–1.500
0.500
5
0
2
2
5
0
5
2
1.700
5
0
10
1
2
2.100
5
–5
–5
–5
–5
2
–6.000
–3.000
–1.200
–0.600
12.00
12.00
12.00
12.00
5
2
2
0
5
5
2
0
5
10
2
0
1992fb
34
LTC1992 Family
APPLICATIONS INFORMATION
Table 1ꢀ Input Signal Liꢃitations for Soꢃe Coꢃꢃon Applications
Single Supply Ground Referenced Single-Ended Input Signal, VOC( at (id-Supplyꢀ (The VINSIG Min and Max values listed account for
both the input common mode limits and the output clipping)
+V
ꢄV
GAIN
ꢁV/Vꢂ
V
V
V
V
V
P-P
V
OUTDIFFꢁ(AXꢂ
S
S
OC(
INREF
INSIGꢁ(AXꢂ
INSIGꢁ(INꢂ
INSIGP-Pꢁ(AXꢂ
ꢁVꢂ
2.7
2.7
2.7
2.7
5
ꢁVꢂ
ꢁVꢂ
1.35
1.35
1.35
1.35
2.5
ꢁVꢂ
ꢁVꢂ
ꢁVꢂ
ꢁV AROUND V
ꢂ
ꢁV
ꢂ
P-PDIFF
INREF
0
1
2
0
0
0
0
0
0
0
0
2.700
1.350
0.540
0.270
5.000
2.500
1.000
0.500
–2.700
–1.350
–0.540
–0.270
–5.000
–2.500
–1.000
–0.500
5.40
2.70
1.08
0.54
10.00
5.00
2.00
1.00
5.40
0
5.40
5.40
5.40
0
5
0
10
1
0
10.00
10.00
10.00
10.00
5
0
2
2.5
5
0
5
2.5
5
0
10
2.5
Single Supply Ground Referenced Single-Ended Input Signal, VOC( at Typical ADC Reference Levelsꢀ (The VINSIG Min and Max values
listed account for both the input common mode limits and the output clipping)
+V
ꢄV
GAIN
ꢁV/Vꢂ
V
V
V
V
V
P-P
V
OUTDIFFꢁ(AXꢂ
S
S
OC(
INREF
INSIGꢁ(AXꢂ
INSIGꢁ(INꢂ
INSIGP-Pꢁ(AXꢂ
ꢁVꢂ
2.7
2.7
2.7
2.7
5
ꢁVꢂ
ꢁVꢂ
ꢁVꢂ
ꢁVꢂ
ꢁVꢂ
ꢁV AROUND V
ꢂ
ꢁV
ꢂ
P-PDIFF
INREF
0
1
2
1
0
0
0
0
0
0
0
0
2.000
1.000
0.400
0.200
4.000
2.000
0.800
0.400
–2.000
–1.000
–0.400
–0.200
–4.000
–2.000
–0.800
–0.400
4.00
2.00
0.80
0.40
8.00
4.00
1.60
0.80
4.00
0
1
4.00
4.00
4.00
8.00
8.00
8.00
8.00
0
5
1
0
10
1
1
0
2
5
0
2
2
5
0
5
2
5
0
10
2
Fully Differential Aꢃplifier Applications
Circuit Analysis
While mathematically correct, the basic signal equation
does not immediately yield any intuitive feel for fully
differential amplifier application operation. However, by
nulling out specific terms, some basic observations and
Allofthepreviousapplicationscircuitdiscussionshaveas-
sumedperfectlymatchedsymmetricalfeedbacknetworks.
To consider the effects of mismatched or asymmetrical
feedback networks, the equations get a bit messier.
sensitivities come forth. Setting β1 equal to β2, V
OSDIFF
to zero and V
to V
gives the old gain equation
OUTCM
OCM
from Figure 3. The ground referenced, single-ended input
signal equation yields the interesting result that the driven
side feedback factor (β1) has a very different sensitivity
than the grounded side (β2). The CMRR is twice the
feedback factor difference divided by the feedback fac-
tor sum. The differential output offset voltage has two
terms. The first term is determined by the input offset
Figure 6 lists the basic gain equation for the differential
output voltage in terms of +V , –V , V
, V
IN
IN OSDIFF OUTCM
and the feedback factors β1 and β2. The feedback factors
are simply the portion of the output that is fed back to the
input summing junction by the R -R resistive voltage
FB IN
divider. β1 and β2 have the range of zero to one. The
V
term also includes its offset voltage, V
, and
term, V
, and the application’s gain. Note that this
OSDIFF
OUTCM
OSCM
its gain mismatch term, K . The K term is determined
term equates to the formula in Figure 3 when β1 equals
β2. The amount of signal level shifting and the feedback
factor mismatch determines the second term. This term
CM
CM
by the matching of the on-chip R
in the common mode level servo (see Figure 2).
and R
resistors
CMP
CMM
1992fb
35
LTC1992 Family
APPLICATIONS INFORMATION
R
FB2
R
R
IN2
IN1
+
–V
+V
+V
–V
–
IN
IN
OUT
OUT
V
V
+V
INDIFF
OUTDIFF
OUT
LTC1992
V
V
OCM
OCM
+V – –V
IN
– –V
IN
OUT
+
–
R
FB1
2[+V • (1 – B1) – (–V ) • (1 – B2)] + 2V
+ 2V
(B1 – B2)
OUTCM
IN
IN
OSDIFF
V
=
OUTDIFF
B1 + B2
WHERE:
R
R
IN2
IN1
B1 =
; B2 =
; V
V
= AMPLIFIER INPUT REFERRED OFFSET VOLTAGE
OSDIFF
R
+ R
R
+ R
IN1
FB1
IN2
FB2
= K • V
+ V
OUTCM
CM
OCM
OSCM
0.999 < K < 1.001
CM
• FOR GROUND REFERENCED, SINGLE-ENDED INPUT SIGNAL, LET +V = V
AND –V = 0V
IN
IN
INSIG
2 • V
• (1 – B1) + 2V
+ 2V
(B1 – B2)
OUTCM
INSIG
OSDIFF
V
=
OUTDIFF
B1 + B2
• COMMON MODE REJECTION: SET +V = –V = V
, V
= 0V, V
= 0V
OUTCM
IN
IN
INCM OSDIFF
ΔV
B1 + B2
B2 – B1
INCM
CMRR =
= 2
; OUTPUT REFERRED
ΔV
OUTDIFF
• OUTPUT DC OFFSET VOLTAGE: SET +V = –V = V
IN
IN
INCM
B2 – B1
B1 + B2
2
V
= V
+ (V
– V
) 2
INCM
OSDIFFOUT
OSDIFF
OUTCM
B1 + B2
1992 F06
Figure 6ꢀ Basic Equations for (isꢃatched or Asyꢃꢃetrical Feedback Applications Circuits
quantifies the undesired effect of signal level shifting
discussed earlier in the Signal Level Shifting section.
split supply voltage applications with a ground referenced
input signal and a grounded V pin.
OCM
The top application circuit in Figure 7 yields a high input
impedance, precision gain of 2 block without any external
resistors. The on-chip common mode feedback servo
resistors determine the gain precision (better than 0.1
Asyꢃꢃetrical Feedback Application Circuits
The basic signal equation in Figure 6 also gives insight
to another piece of intuition. The feedback factors may
be deliberately set to different values. One interesting
class of these application circuits sets one or both of the
feedback factors to the extreme values of either zero or
one. Figure 7 shows three such circuits.
percent). By using the –V
output alone, this circuit is
OUT
also useful to get a precision, single-ended output, high
input impedance inverter. To intuitively understand this
circuit, consider it as a standard op amp voltage follower
(delivered through the signal gain servo) with a comple-
mentaryoutput(deliveredthroughthecommonmodelevel
servo).Asusual,theamplifier’sinputcommonmoderange
must not be exceeded. As with a standard op amp voltage
follower, the common mode signal seen at the amplifier’s
input is the input signal itself. This condition limits the
input signal swing, as well as the output signal swing, to
be the input signal common mode range specification.
At first these application circuits may look to be unstable
or open loop. It is the common mode feedback loop that
enables these circuits to function. While they are useful
circuits, they have some shortcomings that must be con-
sidered.First,duetotheseverefeedbackfactorasymmetry,
the V
level influences the differential output voltage
OCM
with about the same strength as the input signal. With
this much gain in the V path, differential output offset
OCM
and noise increase. The large V
to V
gain also
The middle circuit is largely the same as the first except
OCM
OUTDIFF
necessitates that these circuits are largely limited to dual,
that the noninverting amplifier path has gain. Note that
1992fb
36
LTC1992 Family
APPLICATIONS INFORMATION
+V
V
= 2(+V – V
)
OCM
+
–
–
OUT
OUTDIFF
IN
V
V
LTC1992
OCM
OCM
V
–V
+
IN
OUT
SETTING V
= 0V
OCM
V
V
= 2V
IN
OUTDIFF
R
R
IN
FB
R
1
IN
+V
= 2 +V
(
– V
OCM
; B =
+
–
–
OUT
OUTDIFF
IN
)
B
R
+ R
IN
FB
V
V
LTC1992
OCM
OCM
SETTING V
= 0V
OCM
V
–V
OUT
+
IN
R
1
FB
= 2V 1 +
V
= 2V
IN
IN
(
OUTDIFF
(
)
)
R
B
IN
1 – B
B
R
IN
+V
V
= 2 +V
(
+ V
OCM
; B =
+
–
OUT
OUTDIFF
IN
)
R
+ R
IN
FB
V
V
LTC1992
OCM
OCM
R
IN
SETTING V
= 0V
OCM
V
–V
OUT
+
–
IN
R
R
1 – B
FB
= 2V
IN
V
= 2V
IN
(
)
(
)
OUTDIFF
B
IN
R
FB
1992 F07
Figure 7ꢀ Asyꢃꢃetrical Feedback Application Circuits ꢁ(ost Suitable in Applications with Dual,
Split Supplies ꢁeꢀgꢀ, 5Vꢂ, Ground Referenced Single-Ended Input Signals and VOC( Connected to Groundꢂ
oncetheV
voltageissettozero, thegainformulaisthe
Thebottomcircuitisanothercircuitthatutilizesastandard
opampconfigurationwithacomplementaryoutput.Inthis
case, the standard op amp circuit has an inverting con-
OCM
same as a standard noninverting op amp circuit multiplied
by two to account for the complementary output. Taking
R
FB
to zero (i.e., taking β to one) gives the same formula
figuration. With V
at zero volts, the gain formula is the
OCM
as the top circuit. As in the top circuit, this circuit is also
useful as a single-ended output, high input impedance
inverting gain block (this time with gain). The input com-
mon mode considerations are similar to the top circuit’s,
but are not nearly as constrained since there is now gain
same as a standard inverting op amp circuit multiplied by
two to account for the complementary output. This circuit
does not have any common mode level constraints as the
inverting input voltage sets the input common mode level.
This circuit also delivers rail-to-rail output voltage swing
without any concerns.
in the noninverting amplifier path. This circuit, with V
OCM
at ground, also permits a rail-to-rail output swing in most
applications.
1992fb
37
LTC1992 Family
TYPICAL APPLICATIONS
Interfacing a Bipolar, Ground Referenced, Single-Ended Signal to a Unipolar Single Supply,
Differential Input ADC ꢁVIN = 0V Gives a Digital (id-Scale Codeꢂ
5V
1μF
0.1μF
40k
10k
13.3k
1
8
3
100Ω
100Ω
10k
4
2
3
V
V
1
7
REF
CC
7
6
5
+IN
–IN
+
MID
–
SCK
SERIAL
DATA
V
V
100pF
LTC1864 SDO
LTC1992
2
8
OCM
LINK
2.5V
10k
CONV
GND
+
V
0V
–
6
IN
5
–2.5V
5V
4
1992 TA02a
13.3k
10k
0.1μF
40k
Coꢃpact, Unipolar Serial Data Conversion
5V
1μF
1
8
3
0.1μF
100Ω
100Ω
4
2
3
V
V
1
7
REF
CC
7
6
5
+IN
–IN
+
–
SCK
SERIAL
DATA
LINK
V
V
MID
100pF
LTC1864 SDO
LTC1992-2
2
8
OCM
2.5V
CONV
GND
+
V
–
6
IN
5
0V
4
1992 TA03a
0.1μF
Zero Coꢃponents, Single-Ended Adder/Subtracter
+V
S
0.1μF
3
1
2
8
4
V
V
V1 = V + V – V
B C
+
–
A
A
C
V
LTC1992-2
B
OCM
V
C
+
V2 = V + V – V
–
B
A
5
6
0.1μF
–V
S
1992 TA04
1992fb
38
LTC1992 Family
TYPICAL APPLICATIONS
Single-Ended to Differential Conversion Driving an ADC
2.2μF
10μF
5V 10μF
5V 10μF
10Ω
+
+
+
3
10
36
35
9
V
AV
AV
DD
DV
DD
DGND
REF
DD
SHDN
CS
33
32
31
30
27
LTC1603
CONTROL
LOGIC
μP
CONTROL
LINES
CONVST
RD
REFCOMP
4.375V
7.5k
AND
4
1
2.5V
REF
1.75X
5V
TIMING
+
BUSY
47μF
0.1μF
OV
DD
29
28
5V OR
+
3
3V
+
100Ω
A
IN
4
10μF
1
7
OGND
+
MID
–
+
–
V
V
16-BIT
SAMPLING
ADC
OUTPUT
BUFFERS
B15 TO B0
16-BIT
PARALLEL
BUS
100pF
LTC1992-1
2
8
OCM
–
D15 TO D0
2
A
IN
+
V
–
6
IN
5
100Ω
0.1μF
11 TO 26
1992 TA06a
AGND AGND AGND AGND
V
SS
5
6
7
8
34
10μF
–5V
+
–5V
FFT of the Output Data
0
–10
–20
f
f
= 10.0099kHz
= 333kHz
SNR =85.3dB
THD = –72.1dB
SINAD = –72dB
IN
SAMPLE
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
–130
–140
0
10 20 30 40 50 60 70 80 90 100
FREQUENCY (kHz)
1992 TA06b
1992fb
39
LTC1992 Family
PACKAGE DESCRIPTION
(Sꢆ Package
ꢆ-Lead Plastic (SOP
(Reference LTC DWG # 05-08-1660 Rev F)
3.00 p 0.102
(.118 p .004)
(NOTE 3)
0.52
(.0205)
REF
8
7 6
5
3.00 p 0.102
(.118 p .004)
(NOTE 4)
4.90 p 0.152
(.193 p .006)
0.889 p 0.127
(.035 p .005)
DETAIL “A”
0.254
(.010)
0o – 6o TYP
GAUGE PLANE
5.23
1
2
3
4
3.20 – 3.45
(.206)
0.53 p 0.152
(.021 p .006)
(.126 – .136)
MIN
1.10
(.043)
MAX
0.86
(.034)
REF
DETAIL “A”
0.18
(.007)
0.65
(.0256)
BSC
0.42 p 0.038
(.0165 p .0015)
TYP
SEATING
PLANE
0.22 – 0.38
0.1016 p 0.0508
RECOMMENDED SOLDER PAD LAYOUT
(.009 – .015)
(.004 p .002)
0.65
(.0256)
BSC
TYP
NOTE:
MSOP (MS8) 0307 REV F
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
1992fb
40
LTC1992 Family
REVISION HISTORY
REV
DATE
7/10
6/11
DESCRIPTION
PAGE NU(BER
A
Updated Part Markings
2
B
Revised Features
1
2
Updated to Specified Temperature Range in Absolute Maximum Ratings and Order Information
Revised Block Diagram
24
32
Revised subtitle in Figure 5 of Applications Information section
1992fb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
41
LTC1992 Family
TYPICAL APPLICATION
Balanced Frequency Converter ꢁSuitable for Frequencies up to 50kHzꢂ
60kHz LOW PASS FILTER
SAMPLER
2kHz LOWPASS FILTER
5V
0.1μF
9.53k
0.1μF
0.1μF
37.4k
75k
120pF
1
4
+
390pF
V
3
9.53k
9.53k
8.87k
4
7
8
BNC
BNC
3
+
–
60.4k
1
7
2
8
4
11
7
V
+
–
OUTP
V
MID
330pF
8.87k
LTC1992
2
8
V
MID
BNC
V
180pF
60.4k
OCM
LTC1992
1/2 LTC1043
13
V
OCM
V
INP
+
–
37.4k
12
5
6
V
+
–
OUTM
14
16
5
6
CLK
–
120pF
9.53k
V
390pF
75k
17
0.1μF
0.1μF
0.1μF
10k
0.1μF
V
OCM
1992 TA05a
CLK
–5V
V
= 24kHz
INP
0V
(1V/DIV)
CLK = 25kHz
(LOGIC SQUARE WAVE)
(5V/DIV)
0V
0V
0V
V
= 1kHz
OUTP
(0.5V/DIV)
= 1kHz
V
OUTM
(0.5V/DIV)
1992 TA05b
200μs/DIV
RELATED PARTS
PART NU(BER
LT1167
DESCRIPTION
Precision Instrumentation Amplifier
CO((ENTS
Single Resistor Sets the Gain
LT1990
High Voltage, Gain Selectable Difference Amplifier
Precision Gain Selectable Difference Amplifier
High Speed Gain Selectable Difference Amplifier
Differential In/Out Amplifier Lowpass Filter
250V Common Mode, Micropower, Selectable Gain = 1, 10
Micropower, Pin Selectable Gain = –13 to 14
LT1991
LT1995
30MHz, 1000V/μs, Pin Selectable Gain = –7 to 8
Very Low Noise, Standard Differential Amplifier Pinout
LT6600-X
1992fb
LT 0611 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
42
●
●
© LINEAR TECHNOLOGY CORPORATION 2005
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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