LT1187_06 [Linear]
Low Power Video Difference Amplifi er; 低功耗视频差分功率放大器儿
| 型号： | LT1187_06 |
| 厂家： | 
Linear |
| 描述： | Low Power Video Difference Amplifi er |
| 文件： | 总16页 (文件大小：406K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1187
Low Power
Video Difference Amplifier
FEATURES
DESCRIPTION
The LT®1187 is a difference amplifier optimized for op-
eration on ±±5, or a single ±5 supply and gain ≥2. This
versatileamplifierfeaturesuncommittedhighinputimped-
ance (+) and (–) inputs, and can be used in differential
or single-ended configurations. Additionally, a second
set of inputs give gain adjustment and DC control to the
difference amplifier.
■
Differential or Single-Ended Gain Block (Adjustable)
■
–ꢁdB Bandwidth, A = ±2ꢂ ±0MHz
5
■
Slew Rateꢂ 16±5/µs
■
Low Supply Currentꢂ 1ꢁmA
■
Output Currentꢂ ±20mA
■
CMRR at 10MHzꢂ 40dB
■
LT119ꢁ Pin Compatible
■
Low Cost
The LT1187’s high slew rate, 16±5/ms, wide bandwidth,
±0MHz, and ±20mA output current reꢀuire only 1ꢁmA of
supply current. The shutdown feature reduces the power
dissipationtoamere1±mWandallowsmultipleamplifiers
to drive the same cable.
■
Single ±5 Operation
■
Drives Cables Directly
■
Output Shutdown
■
Available in 8-Lead PDIP and SO Packages
APPLICATIONS
The LT1187 is a low power version of the popular LT119ꢁ,
and is available in 8-pin miniDIPs and SO packages. For
applications with gains of 10 or more, see the LT1189
data sheet.
■
Line Receivers
■
5ideo Signal Processing
■
Cable Drivers
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
■
Tape and Disc Drive Systems
TYPICAL APPLICATION
Cable Sense Amplfier for Loop Through Connections with DC Adjust
Closed-Loop Gain vs Frequency
40
V
IN
V
=
5V
S
L
R
= 1k
5V
30
20
10
0
3
2
+
–
7
CABLE
6
V
LT1187
OUT
1
8
V
+
–
DC
4
–5V
1k
1k
–10
0.1
1
10
100
LT1187 • TA01
FREQUENCY (MHz)
LT1187 • TA02
1187fa
1
LT1187
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
+
–
Total Supply 5oltage (5 to 5 ).................................185
TOP VIEW
ORDER PART
Differential Input 5oltage ..........................................±65
NUMBER
+/REF
–IN
1
2
3
4
–/FB
8
7
6
5
Input 5oltage.............................................................±5
+
S
V
LT1187CN8
LT1187CS8
LT1187IN8
Output Short-Circuit Duration (Note 2) .........Continuous
+IN
OUT
S/D
–
Operating Temperature Range
V
LT1187C .................................................. 0°C to 70°C
LT1187I ............................................... –40°C to 8±°C
LT1187M (OBSOLETE) ...................... –±±°C to 1±0°C
Junction Temperature (Note ꢁ)
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
S8 PART MARKING
1187
T
= 1±0°C, θ = 100°C/W (N8)
JMAX
JA
T
= 1±0°C, θ = 1±0°C/W (S8)
JA
JMAX
J8 PACKAGE 8-LEAD CERDIP
= 17±°C, θ = 100°C/W
Plastic Packages (CN8, CS8) ............................ 1±0°C
Ceramic Packages (CJ8, MJ8) (OBSOLETE)..... 17±°C
Storage Temperature Range................... –6±°C to 1±0°C
Lead Temperature (Soldering, 10 sec) .................. ꢁ00°C
LT1187MJ8
LT1187CJ8
T
JMAX
JA
OBSOLETE PACKAGE
Consider the N8 or S8 Packages for Alternate Source
Order Options Tape and Reelꢂ Add #TR
Lead Freeꢂ Add #PBF Lead Free Tape and Reelꢂ Add #TRPBF
Lead Free Part Markingꢂ httpꢂ//www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
±±5 ELECTRICAL CꢀARACTERISTICS T = 25°C (Note 4)
A
V = 5V, V
= 0V, R = 900Ω from Pins 6 to 8, R = 100Ω from Pin 8 to ground, R = R + R = 1k, C ≤ 10pF, Pin 5 open.
S
REF
FB1
FB2
L
FB1
FB2
L
LT1187C/I/M
MAX
SYMBOL
PARAMETERS
CONDITIONS
MIN
MAX
UNITS
5
Input Offset 5oltage
Either Input (Note ±)
S8 Package
2.0
2.0
10
11
m5
OS
I
I
e
Input Offset Current
Input Bias Current
Input Noise 5oltage
Input Noise Current
Input Resistance
Either Input
Either Input
0.2
±0.±
6±
1.±
100
2.0
1.0
±2.0
µA
µA
n5/√Hz
pA/√Hz
kΩ
OS
B
f = 10kHz
n
O
i
n
f = 10kHz
O
R
C
5
Differential
Either Input
(Note 6)
IN
Input Capacitance
Input 5oltage Limit
pF
m5
IN
±ꢁ80
INLIM
Input 5oltage Range
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Output 5oltage Swing
–2.±
70
70
±ꢁ.8
±6.7
±6.4
ꢁ.±
5
dB
dB
5
5
5
CMRR
PSRR
5
= –2.±5 to ꢁ.±5
100
8±
±4.0
±7.0
±6.8
CM
5 = ±2.ꢁ7±5 to ±85
S
5
OUT
5 = ±±5, R = 1k, A = ±0
S
L
5
5 = ±85, R = 1k, A = ±0
S
L
5
5 = ±85, R = ꢁ00Ω, A = ±0, (Note 4)
S
L
5
G
SR
FPBW
BW
Gain Error
Slew Rate
5 = ±15, A = 10, R = 1k
0.2
16±
±ꢁ
±.7
2ꢁ0
26
1.0
%
5/µs
MHz
MHz
ns
E
O
5
L
(Notes 7, 11)
5 = 15 (Note 8)
100
1±0
Full Power Bandwidth
Small-Signal Bandwidth
Rise Time, Fall Time
Propagation Delay
Overshoot
O
P-P
A = 10
5
t , t
A = ±0, 5 = ±1.±5, 20% to 80% (Note 11)
ꢁ2±
r
f
5
O
t
R = 1k, 5 = ±12±m5, ±0% to ±0%
ns
%
PD
L
O
5 = ±±0m5
O
0
t
Settling Time
Differential Gain
Differential Phase
ꢁ5 Step, 0.1% (Note 9)
100
0.6
0.8
ns
%
s
Diff A5
Diff Ph
R = 1k, A = 4 (Note 10)
L
5
R = 1k, A = 4 (Note 10)
DEG
L
5
P-P
1187fa
2
LT1187
±±5 ELECTRICAL CꢀARACTERISTICS T = 25°C (Note 4)
A
V = 5V, V
= 0V, R = 900Ω from Pins 6 to 8, R = 100Ω from Pin 8 to ground, R = R + R = 1k, C ≤ 10pF, Pin 5 open.
S
REF
FB1
FB2
L
FB1
FB2
L
LT1187C/I/M
MAX
SYMBOL
PARAMETERS
Supply Current
Shutdown Supply Current
Shutdown Pin Current
Turn-On Time
CONDITIONS
MIN
MAX
16
1.±
2±
UNITS
mA
mA
µA
I
1ꢁ
0.8
±
±00
600
S
–
Pin ± at 5
–
I
t
t
Pin ± at 5
S/D
ON
–
Pin ± from 5 to Ground, R = 1k
ns
ns
L
–
Turn-On Time
Pin ± from Ground to 5 , R = 1k
OFF
L
±5 ELECTRICAL CꢀARACTERISTICS T = 25°C (Note 4)
open.
A
FB2
+
–
V
S
= 5V, V = 0V, V
= 2.5V, R = 900Ω from Pins 6 to 8, R = 100Ω from Pin 8 to V , R = R + R = 1k, C ≤ 10pF, Pin 5
S
REF
FB1
REF
L
FB1
FB2
L
LT1187C/I/M
TYP
SYMBOL
PARAMETER
CONDITIONS
MIN
MAX
UNITS
5
Input Offset 5oltage
Either Input (Note ±)
SO Package
2.0
2.0
10
12
m5
m5
OS
I
I
Input Offset Current
Input Bias Current
Input 5oltage Range
Common Mode Rejection Ratio
Output 5oltage Swing
Either Input
Either Input
0.2
±0.±
1.0
±2.0
ꢁ.±
µA
µA
5
dB
5
OS
B
2.0
70
ꢁ.6
CMRR
5
5
CM
= 2.05 to ꢁ.±5
100
4.0
0.1±
1ꢁ0
±.ꢁ
12
R = ꢁ00Ω to Ground
5
5
High
Low
OUT
L
OUT
(Note 4)
0.4
5
OUT
SR
BW
Slew Rate
Small-Signal Bandwidth
Supply Current
Shutdown Supply Current
Shutdown Pin Current
5 = 1.±5 to ꢁ.±5
5/µs
MHz
mA
mA
µA
O
A = 10
5
I
S
1±
1.±
2±
Pin ± at 5–
Pin ± at 5–
0.8
±
I
S/D
±±5 ELECTRICAL CꢀARACTERISTICS –55°C ≤ T ≤ 125°C (Note 4)
A
V = 5V, V
= 0V, R = 900Ω from Pins 6 to 8, R = 100Ω from Pin 8 to ground, R = R + R = 1k, C ≤ 10pF, Pin 5 open.
S
REF
FB1
FB2
L
FB1
FB2
L
LT1187M
TYP
2.0
8.0
0.2
±0.±
SYMBOL
PARAMETER
Input Offset 5oltage
CONDITIONS
Either Input (Note ±)
MIN
MAX
1±
UNITS
m5
m5/°C
µA
5
OS
Δ5 /ΔT
Input 5 Drift
OS
OS
I
OS
I
B
Input Offset Current
Input Bias Current
Input 5oltage Range
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Output 5oltage Swing
Either Input
Either Input
1.±
±ꢁ.±
ꢁ.±
µA
5
dB
dB
5
5
5
–2.±
70
60
±ꢁ.7
±6.6
±6.4
CMRR
PSRR
5
CM
= –2.±5 to ꢁ.±5
100
8±
±4.0
±7.0
±6.8
5 = ±2.ꢁ7±5 to ±85
S
5
5 = ±±5, R = 1k, A = ±0
OUT
S
L
5
5
5 = ±85, R = 1k, A = ±0
S
L
5 = ±85, R = ꢁ00Ω, A = ±0 (Note 4)
S
L
5
G
Gain Error
Supply Current
Shutdown Supply Current
Shutdown Pin Current
5 = ±15, A = 10, R = 1k
0.2
1ꢁ
0.8
±
1.2
17
1.±
2±
%
mA
mA
µA
E
O
5
L
I
S
–
Pin ± at 5 (Note 12)
–
I
Pin ± at 5
S/D
1187fa
3
LT1187
±±5 ELECTRICAL CꢀARACTERISTICS 0°C ≤ T ≤ 70°C (LT1187C) –40°C ≤ T ≤ 85°C (LT1187I) (Note 4)
A
A
V = 5V, V
S
= 0V, R = 900Ω from Pins 6 to 8, R = 100Ω from Pin 8 to ground, R = R + R = 1k, C ≤ 10pF, Pin 5 open.
REF
FB1
FB2
L
FB1
FB2
L
LT1187C/I
SYMBOL
PARAMETER
Input Offset 5oltage
CONDITIONS
Either Input (Note ±)
MIN
TYP
2.0
9.0
0.2
±0.±
MAX
12
UNITS
m5
m5/°C
µA
5
OS
Δ5 /ΔT
Input 5 Drift
OS
OS
I
OS
I
B
Input Offset Current
Input Bias Current
Input 5oltage Range
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Output 5oltage Swing
Either Input
Either Input
1.±
±ꢁ.±
ꢁ.±
µA
5
dB
dB
5
5
5
–2.±
70
6±
±ꢁ.7
±6.6
±6.4
CMRR
PSRR
5
CM
= –2.±5 to ꢁ.±5
100
8±
±4.0
±7.0
±6.8
5 = ±2.ꢁ7±5 to ±85
S
5
OUT
5 = ±±5, R = 1k, A = ±0
S
L
5
5
5 = ±85, R = 1k, A = ±0
S
L
5 = ±85, R = ꢁ00Ω, A = ±0 (Note 4)
S
L
5
G
Gain Error
Supply Current
Shutdown Supply Current
Shutdown Pin Current
5 = ±15, A = 10, R = 1k
0.2
1ꢁ
0.8
±
1.0
17
1.±
2±
%
mA
mA
µA
E
O
5
L
I
S
–
Pin ± at 5 (Note 12)
–
I
Pin ± at 5
S/D
±5 ELECTRICAL CꢀARACTERISTICS 0°C ≤ T ≤ 70°C (LT1187C) –40°C ≤ T ≤ 85°C (LT1187I) (Note 4)
A
A
FB1
+
–
V
= 5V, V = 0V, V
= 2.5V, R = 900Ω from Pins 6 to 8, R = 100Ω from Pin 8 to V , R = R + R = 1k, C ≤ 10pF, Pin 5
S
S
REF
FB1
FB2
REF
L
FB2
L
open.
LT1187C/I
TYP
SYMBOL
PARAMETER
CONDITIONS
MIN
MAX
UNITS
5
Input Offset 5oltage
Either Input (Note ±)
SO Package
2.0
2.0
12.0
1ꢁ.0
m5
m5
OS
Δ5 /ΔT
Input 5 Drift
9.0
0.2
±0.±
µ5/°C
µA
µA
5
OS
OS
I
I
Input Offset Current
Input Bias Current
Input 5oltage Range
Common Mode Rejection Ratio
Output 5oltage Swing
Either Input
Either Input
1.±
±ꢁ.±
ꢁ.±
OS
B
2.0
70
ꢁ.±
CMRR
5
CM
= 2.05 to ꢁ.±5
100
4.0
0.1±
12
0.8
±
dB
5
5
OUT
R = ꢁ00Ω to Ground
5
5
High
Low
L
OUT
(Note 4)
0.4
16
1.±
2±
5
OUT
I
I
Supply Current
Shutdown Supply Current
Shutdown Pin Current
mA
mA
µA
S
–
Pin ± at 5 (Note 12)
–
Pin ± at 5
S/D
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.
Note 2: A heat sink may be reꢀuired to keep the junction temperature
below absolute maximum when the output is shorted continuously.
Note 6: 5
is the maximum voltage between –5 and +5 (Pin 2 and
IN IN
IN LIM
Pin ꢁ) for which the output can respond.
Note 7: Slew rate is measured between ±0.±5 on the output, with a 5
step of ±0.7±5, A = ꢁ and R = 1k.
Note 8: Full power bandwidth is calculated from the slew rate
measurementꢂ FPBW = SR/2π5 .
Note 9: Settling time measurement techniꢀues are shown in “Take the
Guesswork Out of Settling Time Measurements,” EDN, September 19,
198±.
IN
5
L
P
Note 3: T is calculated from the ambient temperature T and power
J
A
dissipation P according to the following formulasꢂ
D
LT1187MJ8, LT1187CJ8ꢂ T = T + (P • 100°C/W)
J
A
D
LT1187CN8ꢂ
LT1187CS8ꢂ
T = T + (P • 100°C/W)
J A D
Note 10: NTSC (ꢁ.±8MHz).
T = T + (P • 1±0°C/W)
Note 11: AC parameters are 100% tested on the ceramic and plastic DIP
packaged parts (J8 and N8 suffix) and are sample tested on every lot of
the SO packaged parts (S8 suffix).
J
A
D
Note 4: When R = 1k is specified, the load resistor is R + R , but
L
FB1
FB2
when R = ꢁ00Ω is specified, then an additional 4ꢁ0Ω is added to the
L
output such that (R + R ) in parallel with 4ꢁ0Ω is R = ꢁ00Ω.
Note 12: See Application section for shutdown at elevated temperatures.
FB1
FB2
L
Do not operate shutdown above T > 12±°C.
Note 5: 5 measured at the output (Pin 6) is the contribution from both
J
OS
input pair and is input referred.
1187fa
4
LT1187
TYPICAL PERFORMANCE CꢀARACTERISTICS
Input Bias Current vs
Common Mode Voltage vs
Common Mode Voltage
Temperature
Input Bias Current vs Temperature
+
V
100
0
3.0
2.5
V
= 5V
S
+
–0.5
–1.0
–1.5
–2.0
V
= 1.8V TO 9V
+I
B
2.0
1.5
1.0
0.5
–100
–200
–300
–400
–I
B
I
OS
–55°C
2.0
1.5
1.0
0.5
25°C
+
V
= –1.8V TO –9V
0
125°C
–
–0.5
V
–5 –4 –3 –2 –1
0
1
2
3
4
5
–50 –25
0
25
50
75 100 125
–50 –25
0
25
50
75
100 125
TEMPERATURE (°C)
COMMON MODE VOLTAGE (V)
TEMPERATURE (°C)
LT1187 • TPC02
LT1187 • TPC03
LT1187 • TPC01
Equivalent Input Noise Current vs
Frequency
Equivalent Input Noise Voltage vs
Frequency
Supply Current vs Supply Voltage
600
500
400
300
200
100
0
12
10
8
16
14
12
10
8
V
T
= 5V
V
T
= 5V
= 25°C
= 0Ω
S
S
= 25°C
A
A
R
= 100k
R
S
S
–55°C
25°C
6
125°C
4
2
0
10
100
1k
10k
100k
10
100
1k
10k
100k
0
2
4
6
8
10
FREQUENCY (Hz)
FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
LT1187 • TPC04
LT1187 • TPC05
LT1187 • TPC06
Shutdown Supply Current vs
Temperature
Gain Error vs Temperature
Open-Loop Gain vs Temperature
6
5
4
3
2
1
0
8
6
4
2
0
0
V
V
=
=
5V
3V
V
V
A
=
5V
2V
S
O
S
OUT
V
R
V
= 5V
S
=
= 10
= 1k
R
= 1k
L
L
–0.05
–0.10
–0.15
–0.20
V
= –V + 0.6V
EE
S/D
V
S/D
= –V + 0.4V
EE
R
= 500Ω
L
V
= –V + 0.2V
EE
S/D
V
= –V
EE
S/D
–50 –25
0
25
50
75 100 125
–50 –25
0
25
50
75 100 125
–50 –25
0
25
50
75 100 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
LT1187 • TPC07
LT1187 • TPC08
LT1187 • TPC09
1187fa
5
LT1187
TYPICAL PERFORMANCE CꢀARACTERISTICS
Open-Loop Voltage Gain vs
Load Resistance
Gain Bandwidth Product vs
Supply Voltage
Gain, Phase vs Frequency
100
80
60
40
20
0
100
80
16k
12k
8k
60
50
A
= 20dB
V
T
= 5V
V
V
T
=
=
5V
3V
V
S
S
O
A
T
= –55°C
A
T
= 25°C
A
PHASE
R
= 1k
= 25°C
L
= 25°C
A
60
T
= 125°C
A
40
20
0
GAIN
40
30
4k
–20
100k
–20
0
1M
10M
100M
100
1k
10k
0
2
4
6
8
10
FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
LOAD RESISTANCE (Ω)
LT1187 • TPC11
LT1187 • TPC12
LT1187 • TPC10
Gain Bandwidth Product and
Unity Gain Phase Margin vs
Temperature
Common Mode Rejection Ratio
vs Frequency
Output Impedance vs Frequency
65
55
45
35
100
60
50
40
30
80
V
T
=
5V
V
=
5V
V
T
= 5V
S
S
A
S
L
= 25°C
R
= 1k
= 25°C
A
R
= 1k
L
70
60
GAIN BANDWIDTH
PRODUCT
10
1.0
0.1
50
40
30
A
= 10
= 2
V
UNITY GAIN
PHASE MARGIN
A
V
1k
10k
100k
1M
10M
100M
–50 –25
0
25
50
75 100 125
100k
1M
10M
100M
TEMPERATURE (°C)
FREQUENCY (Hz)
FREQUENCY (Hz)
LT1187 • TPC13
LT1187 • TPC14
LT1187 • TPC15
Power Supply Rejection Ratio vs
Frequency
Output Short-Circuit Current vs
Temperature
Output Swing vs Supply Voltage
+
V
–0.7
–0.8
–0.9
–1.0
–1.1
36
35
80
V
= 5V
S
A
V
= 5V
S
T
= 25°C
125°C
V
=
300mV
RIPPLE
60
40
20
0
25°C
34
33
32
31
30
+PSRR
–PSRR
–55°C
R
= 1k
L
1.8V ≤ V
≤ 9V
S
125°C
25°C
0.5
0.4
0.3
–55°C
0.2
0.1
–20
–
0
2
4
6
8
10
–50 –25
0
25
50
75
100 125
1k
10k
100k
1M
10M
100M
V
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
FREQUENCY (Hz)
LT1187 • TPC17
LT1187 • TPC18
LT1187 • TPC16
1187fa
6
LT1187
TYPICAL PERFORMANCE CꢀARACTERISTICS
Output Voltage Swing vs
Load Resistance
Output Voltage Step vs
Settling Time, A = 2
Slew Rate vs Temperature
V
4
2
5
3
250
200
150
V
T
= 5V
V
= 5V
S
S
L
O
V
V
=
5V
S
= 25°C
R
V
= 1k
A
R
= 1k
=
= 2
0.5V
L
T
A
= –55°C
10mV
A
T
= 25°C
A
–SLEW RATE
T
= 125°C
A
1
0
+SLEW RATE
–1
–3
–5
T
= 25°C
A
–2
–4
10mV
T
= –55°C
T
A
= 125°C
A
40
50
60
70
80
90
100
10
100
LOAD RESISTANCE (Ω)
1000
–50 –25
0
25
50
75 100 125
SETTLING TIME (ns)
TEMPERATURE (°C)
LT1187 • TPC19
LT1187 • TPC21
LT1187 • TPC20
Harmonic Distortion vs
Output Voltage
Large-Signal Transient Response
–30
–35
–40
–45
–50
–55
–60
V
= 5V
S
A
L
T
= 25°C
R
= 1k
f = 1MHz
HD
A
= 10
3
V
HD
2
4
6
7
0
1
2
3
5
LT1187 • TPC2ꢁ
OUTPUT VOLTAGE (V
)
P-P
INPUT IN LIMITING, A = ꢁ, SR = 1805/µs
5
LT1187 • TPC22
Small-Signal Transient Response
Small-Signal Transient Response
LT1187 • TPC24
LT1187 • TPC2±
A
5
= 2, R = 1k, O5ERSHOOT = 2±%
A = 2, R = 1k, O5ERSHOOT = 2±%
5 FB
FB
1187fa
7
LT1187
APPLICATIONS INFORMATION
Power Supply Bypassing
The primary use of the LT1187 is in converting high speed
differential signals to a single-ended output. The LT1187
video difference amplifier has two uncommitted high
input impedance (+) and (–) inputs. The amplifier has
another set of inputs which can be used for reference and
feedback. Additionally, this set of inputs give gain adjust
and DC control to the difference amplifier. The voltage
gain of the LT1187 is set like a conventional operational
amplifier. Feedback is applied to Pin 8, and it is optimized
for gains of 2 or greater. The amplifier can be operated
single-ended by connecting either the (+) or (–) inputs to
the +/REF (Pin 1). The voltage gain is set by the resistorsꢂ
The LT1187 is ꢀuite tolerant of power supply bypassing.
Insomeapplicationsa0.1µFceramicdisccapacitorplaced
1/2 inch from the amplifier is all that is reꢀuired. In ap-
plications reꢀuiring good settling time, it is important to
use multiple bypass capacitors. A 0.1µF ceramic disc in
parallel with a 4.7µF tantalum is recommended.
Calculating the Output Offset Voltage
Both input stages contribute to the output offset voltage at
Pin 6. The feedback correction forces balance in the input
stages by introducing an input 5 at Pin 8. The complete
expression for the output offset voltage isꢂ
OS
(R + R )/R .
FB
G
G
Like the single-ended case, the differential voltage gain is
setbytheexternalresistorsꢂ(R +R )/R . Themaximum
5
OUT
=(5 +I (R )+I (R ))•(R +R )/R +I (R )
OS OS S B REF FB G G B FB
FB
G
G
input differential signal for which the output will respond
is approximately ±0.ꢁ85.
R represents the input source resistance, typically 7±Ω,
S
and R represents the finite source impedance from the
REF
DC reference voltage, for 5 grounded, R = 0Ω. The
REF
REF
S/D
S/D
I
is normally a small contributor and the expression
OS
+
+
V
V
5
5
simplifies toꢂ
3
2
3
2
7
7
V
+
IN
+
V
–
IN
–
6
6
5
= 5 (R + R )/R + I (R )
LT1187
LT1187
+/REF
–/FB
OUT
OS FB
G
G
B
FB
V
V
OUT
1
8
1
8
OUT
+/REF
–/FB
If R is limited to 1k the last term of the eꢀuation con-
4
4
FB
–
–
tributes only 2m5, since I is less than 2µA.
V
V
B
R
FB
R
FB
+
7
V
R
+
+
R
G
FB
R
R
G
FB
A
= +
V
R
G
A
V
= –
R
G
R
G
R
G
6
S/D
S/D
+
+
V
V
R
FB
5
5
3
2
3
2
8
Q1
Q2
Q3
Q4
7
7
+
+
V
V
IN DIFF
IN DIFF
–
–
6
6
LT1187
LT1187
+/REF
–/FB
R
G
V
V
OUT
1
8
1
8
OUT
3
2
1
REF
+
+
–
V
R
R
E
1.1k
+/REF
–/FB
IN
E
R
G
1.1k
V
+
IN
R
4
4
–
R
S
R
R
REF
S
–
V
R
V
R
345 A
350 A
FB
FB
–
4
V
ILT1187 • F01
R
FB
R
+R
G
R
G
FB
FB
V
= (V
+ V
)
V
O
=
V
–
V
IN
O
IN DIFF
IN
IN DIFF
(
(
(
(
R
G
R
R
R
G
G
G
LT1187 • AI01
Figure 1. Simplified Input Stage Schematic
1187fa
8
LT1187
APPLICATIONS INFORMATION
Operating with Low Closed-Loop Gains
Small-Signal Transient Response
The LT1187 has been optimized for closed-loop gains
of 2 or greater. For a closed-loop gain of 2 the response
peaks about 2dB. Peaking can be eliminated by placing a
capacitor across the feedback resistor, (feedback zero).
This peaking shows up as time domain overshoot of
about 2±%.
Closed-Loop Voltage Gain vs Frequency
9
8
C
= 0pF
FB
LT1187 • AI0±
7
6
5
A
5
= 2, WITH 8pF FEEDBACK CAPACITOR
Extending the Input Range
C
= 5pF
FB
4
3
2
Figure 1 shows a simplified schematic of the LT1187. In
normal operation REF, Pin 1, is grounded or taken to a DC
offset control voltage and differential signals are applied
between Pins 2 and ꢁ. The input responds linearly until
all of the ꢁ4±µA current flows through the 1.1k resistor
and Q1 (or Q2) turns off. Therefore the maximum input
C
= 10pF
FB
V
T
V
R
R
= 5V
S
A
= 25°C
1
0
A
= 2
= 900Ω
FB
G
= 900Ω
–1
100k
1M
10M
100M
FREQUENCY (Hz)
LT1187 • AI03
swing is ꢁ80m5 or 760m5 . The second differential
P
P-P
pair, Qꢁ and Q4, is running at slightly larger current so
that when the first input stage limits, the second stage
remains biased to maintain the feedback.
Small-Signal Transient Response
Occasionally it is necessary to handle signals larger than
760m5
at the input. The LT1187 input stage can be
P-P
tricked to handle up to 1.±5 . To do this, it is necessary
P-P
to ground Pin ꢁ and apply the differential input signal
between Pins 1 and 2. The input signal is now applied
across two 1.1k resistors in series. Since the input signal
is applied to both input pairs, the first pair will run out of
bias current before the second pair, causing the amplifier
to go open loop. The results of this techniꢀue are shown
in the following scope photo.
LT1187 • AI04
A
5
= 2, O5ERSHOOT = 2±%, R = R = 1k
FB G
1187fa
9
LT1187
APPLICATIONS INFORMATION
LT1187 in Unity Gain
PerformanceCharacteristicssection.Atveryhighelevated
temperature it is important to hold the shutdown pin close
to the negative supply to keep the supply current from
increasing.
Send Color Video Over Twisted-Pair
With an LT1187 it is possible to send and receive color
compositevideosignalsmorethan1000feetonalowcost
twisted-pair. A bi-directional “video bus” consists of the
LT119± op amp and the LT1187 video difference amplifier.
A pair of LT119±s at Transmit 1 is used to generate dif-
ferential signals to drive the line which is back-terminated
in its characteristic impedance. The LT1187 twisted-pair
receiverconvertssignalsfromdifferentialtosingle-ended.
Topology of the LT1187 provides for cable compensation
at the amplifier’s feedback node as shown. In this case,
1000 feet of twisted-pair is compensated with 1000pF
and ±0Ω to boost the ꢁdB bandwidth of the system from
7±0kHz to 4MHz. This bandwidth is adeꢀuate to pass a
ꢁ.±8MHz chroma subcarrier and the 4.±MHz sound sub-
carrier. Attenuation in the cable can be compensated by
LT1187 • AI06
(A) STANDARD INPUTS, PINS 2 TO ꢁ, 5 = 1.05
IN
P-P
P-P
P-P
(B) EXTENDED INPUTS, PINS 2 TO 2, 5 = 1.05
IN
(C) EXTENDED INPUTS, PINS 1 TO 2, 5 = 2.05
IN
Using the Shutdown Feature
The LT1187 has a uniꢀue feature that allows the amplifier
to be shutdown for conserving power, or for multiplexing
several amplifiers onto a common cable. The amplifier
–
will shut down by taking Pin ± to 5 . In shutdown, the
amplifier dissipates 1±mW while maintaining a true high
impedanceoutputstateof20kinparallelwiththefeedback
resistors. For MUX applications, the amplifiers may be
configured inverting, noninverting or differential. When
the output is loaded with as little 1k from the amplifier’s
feedback resistors, the amplifier shuts off in 600ns. This
shutoff can be under the control of HC CMOS operating
between 05 and –±5.
lowering the gain set resistor R . At Transmit 2, another
G
pair of LT119±s serve the dual function to provide cable
termination via low output impedance, and generate dif-
ferential signals for Transmit 2. Cable termination is made
up of a 1±Ω and ꢁꢁΩ attenuator to reduce the differential
input signal to the LT1187. Maximum input signal for the
LT1187 is 760m5
.
P-P
The ability to maintain shutoff is shown on the curve
Shutdown Supply Current vs Temperature in the Typical
1.5MHz Square Wave Input and Unequalized Response
Through 1000 Feet of Twisted-Pair
1MHz Sine Wave Gated Off with Shutdown Pin
LT1187 • AI07
LT1187 • AI08
A
5
= 2, R = R = 1k
FB G
1187fa
10
LT1187
APPLICATIONS INFORMATION
1.5MHz Square Wave Input and Equalized Response
Through 1000 Feet of Twisted-Pair
Multiburst Pattern Passed Through
1000 Feet of Twisted-Pair
LT1187 • AI09
LT1187 • AI10
Bi-Directional Video Bus
TRANSMIT 1
TRANSMIT 2
3
3
+
+
6
6
1k
1k
LT1195
1k
LT1195
75Ω
75Ω
2
2
–
–
1k
1k
1k
1k
1k
2
3
2
3
–
+
–
+
6
6
LT1195
LT1195
33Ω
15Ω
33Ω
15Ω
33Ω
15Ω
33Ω
S/D
5
S/D
5
3
2
1
8
3
+
–
+
–
+
–
+
15Ω
2
1
8
75Ω
75Ω
6
6
LT1187
LT1187
1000 FEET
TWISTED-PAIR
–
R
R
FB
300Ω
FB
300Ω
1000pF
1000pF
50Ω
R
R
300Ω
G
G
50Ω
300Ω
LT1187 • AI11
RECEIVE 2
RECEIVE 1
1187fa
11
LT1187
SIMPLIFIED SCꢀEMATIC
+
V
7
+
+
V
V
BIAS
BIAS
C
M
+
3
C
FF
2
–
V
6
+V
+V
OUT
*
–
V
4
5
S/D
1
+/REF
8
–/FB
* SUBSTRATE DIODE, DO NOT FORWARD BIAS
LT1187 • SS
1187fa
12
LT1187
PACKAGE DESCRIPTION
J8 Package
8-Lead CERDIP (Narrow .300 Inch, Hermetic)
(Reference LTC DWG # 0±-08-1110)
.405
(10.287)
MAX
CORNER LEADS OPTION
(4 PLCS)
.005
(0.127)
MIN
6
5
4
8
7
.023 – .045
(0.584 – 1.143)
HALF LEAD
OPTION
.025
.220 – .310
(5.588 – 7.874)
.045 – .068
(0.635)
RAD TYP
(1.143 – 1.650)
FULL LEAD
OPTION
1
2
3
.200
(5.080)
MAX
.300 BSC
(7.62 BSC)
.015 – .060
(0.381 – 1.524)
.008 – .018
(0.203 – 0.457)
0– 15
.045 – .065
(1.143 – 1.651)
.125
3.175
MIN
NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE
OR TIN PLATE LEADS
.014 – .026
(0.360 – 0.660)
.100
(2.54)
BSC
J8 0801
OBSOLETE PACKAGE
1187fa
13
LT1187
PACKAGE DESCRIPTION
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 0±-08-1±10)
.400*
(10.160)
MAX
8
7
6
5
4
.255 .015*
(6.477 0.381)
1
2
3
.130 .005
.300 – .325
.045 – .065
(3.302 0.127)
(1.143 – 1.651)
(7.620 – 8.255)
.065
(1.651)
TYP
.008 – .015
(0.203 – 0.381)
.120
.020
(0.508)
MIN
(3.048)
MIN
+.035
.325
–.015
.018 .003
(0.457 0.076)
.100
(2.54)
BSC
+0.889
8.255
(
)
N8 1002
–0.381
NOTE:
INCHES
1. DIMENSIONS ARE
MILLIMETERS
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
1187fa
14
LT1187
PACKAGE DESCRIPTION
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 0±-08-1610)
.189 – .197
(4.801 – 5.004)
.045 .005
NOTE 3
.050 BSC
7
5
8
6
.245
MIN
.160 .005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
.030 .005
TYP
1
3
4
2
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
(0.254 – 0.508)
× 45°
.053 – .069
(1.346 – 1.752)
.004 – .010
(0.101 – 0.254)
.008 – .010
(0.203 – 0.254)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
.050
(1.270)
BSC
.014 – .019
(0.355 – 0.483)
TYP
NOTE:
INCHES
1. DIMENSIONS IN
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
SO8 0303
1187fa
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.
15
LT1187
RELATED PARTS
PART NUMBER
LT1189
DESCRIPTION
Low Power 5ideo Difference Amplifier
Adjustable Gain 5ideo Difference Amplifier
Gain = 10 5ideo Difference Amplifier
2±0mA Out, 9005/µs, 60MHz CFA
1mA, 12MHz 4005/µs Op Amplifier
ꢁ.ꢁ5 5ideo Difference Amplifier
LT119ꢁ
LT1194
LT1206
LT1ꢁ±4
LT6±±2
LT6±±9
Low Cost ±5/±±5 Triple 5ideo Amplifier with Shutdown
1187fa
LT 1006 REV A • PRINTED IN USA
16 LinearTechnology Corporation
16ꢁ0 McCarthy Blvd., Milpitas, CA 9±0ꢁ±-7417
●
●
© LINEAR TECHNOLOGY CORPORATION 1993
(408) 4ꢁ2-1900 FAXꢂ (408) 4ꢁ4-0±07 www.linear.com
相关型号：
LT1189CN8#PBF
LT1189 - Low Power Video Difference Amplifier; Package: PDIP; Pins: 8; Temperature Range: 0°C to 70°C
Linear
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