LT1227_06 [Linear]
140MHz Video Current Feedback Amplifier; 140MHz的视频电流反馈放大器
| 型号： | LT1227_06 |
| 厂家： | 
Linear |
| 描述： | 140MHz Video Current Feedback Amplifier |
| 文件： | 总12页 (文件大小：244K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1227
140MHz Video Current
Feedback Amplifier
U
FEATURES
DESCRIPTIO
The LT®1227 is a current feedback amplifier with wide
bandwidth and excellent video characteristics. The low
differential gain and phase, wide bandwidth, and 30mA
output drive current make the LT1227 well suited to drive
cables in video systems.
■
140MHz Bandwidth: AV = 2, RL = 150Ω
■
1100V/µs Slew Rate
■
Low Cost
■
30mA Output Drive Current
■
0.01% Differential Gain
■
0.01° Differential Phase
Ashutdownfeatureswitchesthedeviceintoahighimped-
ance, low current mode, allowing multiple devices to be
connected in parallel and selected. Input to output isola-
tioninshutdownis70dBat10MHzforinputamplitudesup
to 10VP-P. The shutdown pin interfaces to open collector
oropendrainlogicandtakesonly4µstoenableordisable.
■
High Input Impedance: 14MΩ, 3pF
■
Wide Supply Range: ±2V to ±15V
■
Shutdown Mode: IS < 250µA
■
Low Supply Current: IS = 10mA
■
Inputs Common Mode to Within 1.5V of Supplies
■
Outputs Swing Within 0.8V of Supplies
The LT1227 comes in the industry standard pinout and
can upgrade the performance of many older products. For
a dual or quad version, see the LT1229/1230 data sheet.
U
APPLICATIO S
■
Video Amplifiers
The LT1227 is manufactured on Linear Technology’s
proprietary complementary bipolar process.
■
Cable Drivers
■
RGB Amplifiers
Test Equipment Amplifiers
50Ω Buffers for Driving Mixers
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
U
TYPICAL APPLICATIO
Video Cable Driver
Differential Gain and Phase
vs Supply Voltage
0.20
0.16
0.12
0.08
0.04
0
0.20
0.16
0.12
0.08
0.04
0
V
NTSC COMPOSITE
f = 3.58MHz
+
IN
75Ω
LT1227
–
75Ω
CABLE
R
F
1k
V
OUT
R
1k
G
75Ω
V
V
OUT
= 1
∆φ
IN
1227 TA01
∆G
5
7
9
11
13
15
SUPPLY VOLTAGE (±V)
LT1227 • TA02
1
LT1227
W W W
U
W
U
ABSOLUTE AXI U RATI GS
/O
PACKAGE RDER I FOR ATIO
(Note 1)
ORDER PART
NUMBER
Supply Voltage ..................................................... ±18V
Input Current ...................................................... ±15mA
Output Short Circuit Duration (Note 2) ........ Continuous
Operating Temperature Range
LT1227C.................................................. 0°C to 70°C
LT1227M (OBSOLETE) .................... –55°C to 125°C
Storage Temperature Range ................. –65°C to 150°C
Junction Temperature
TOP VIEW
1
2
3
4
NULL
–IN
8
7
6
5
SHDN
+
LT1227CN8
V
+IN
OUT
–
V
NULL
N8 PACKAGE
8-LEAD PLASTIC DIP
TJMAX = 150°C, θJA = 100°C/W (N)
J8 PACKAGE
8-LEAD CERAMIC DIP
TJMAX = 175°C, θJA = 100°C/W (J)
Plastic Package ................................................ 150°C
Ceramic Package (OBSOLETE) ........................ 175°C
Lead Temperature (Soldering, 10 sec.)................ 300°C
LT1227MJ8
OBSOLETE PACKAGE
Consider the N8 Package for Alternate Source.
TOP VIEW
ORDER PART
NUMBER
1
2
3
4
8
7
6
5
NULL
–IN
SHDN
+
V
LT1227CS8
+IN
OUT
–
V
NULL
S8 PART MARKING
1227
S8 PACKAGE
8-LEAD PLASTIC SO
JMAX = 150°C, θJA = 150°C/W
T
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCM = 0, ±5V ≤ VS ≤ ±15V, pulse tested, unless otherwise noted.
SYMBOL
PARAMETER
Input Offset Voltage
CONDITIONS
T = 25°C
MIN
TYP
±3
MAX
±10
±15
UNITS
V
mV
mV
µV/°C
OS
A
●
●
Input Offset Voltage Drift
Noninverting Input Current
10
±0.3
I
I
+
–
T = 25°C
A
±3
±10
±60
±100
µA
µA
µA
µA
IN
IN
●
●
Inverting Input Current
T = 25°C
A
±10
e
+i
–i
R
Input Noise Voltage Density
f = 1kHz, R = 1k, R = 10Ω, R = 0Ω
f = 1kHz
f = 1kHz
3.2
1.7
32
14
11
nV/√Hz
pA/√Hz
pA/√Hz
n
F
G
S
Noninverting Input Noise Current Density
Inverting Input Noise Current Density
Input Resistance
n
n
V
V
= ±13V, V = ±15V
●
●
1.5
1.5
MΩ
MΩ
IN
IN
IN
S
= ±3V, V = ±5V
S
C
Input Capacitance
3
pF
IN
Input Voltage Range
V = ±15V, T = 25°C
±13
±12
±3
±13.5
V
V
V
V
S
A
●
●
V = ±5V, T = 25°C
±3.5
S
A
±2
CMRR
Common Mode Rejection Ratio
V = ±15V, V = ±13V, T = 25°C
55
55
55
55
62
61
dB
dB
dB
dB
S
CM
A
V = ±15V, V = ±12V
●
●
S
CM
V = ±5V, V = ±3V, T = 25°C
S
CM
A
V = ±5V, V = ±2V
S
CM
2
LT1227
The ● denotes the specifications which apply over the full operating
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifications are at TA = 25°C. VCM = 0, ±5V ≤ VS ≤ ±15V, pulse tested, unless otherwise noted.
SYMBOL
PARAMETER
Inverting Input Current
Common Mode Rejection
CONDITIONS
V = ±15V, V = ±13V, T = 25°C
MIN
TYP
3.5
MAX
UNITS
10
10
10
10
µA/V
µA/V
µA/V
µA/V
dB
dB
nA/V
nA/V
µA/V
µA/V
S
CM
A
V = ±15V, V = ±12V
●
●
S
CM
V = ±5V, V = ±3V, T = 25°C
4.5
80
S
CM
A
V = ±5V, V = ±2V
S
CM
PSRR
Power Supply Rejection Ratio
V = ±2V to ±15V, T = 25°C
60
60
S
A
V = ±3V to ±15V
●
●
●
S
Noninverting Input Current
Power Supply Rejection
Inverting Input Current
Power Supply Rejection
V = ±2V to ±15V, T = 25°C
2
50
50
5
5
S
A
V = ±3V to ±15V
S
V = ±2V to ±15V, T = 25°C
0.25
S
A
V = ±3V to ±15V
S
A
Large-Signal Voltage Gain
V = ±15V, V
= ±10V, R = 1k
●
●
55
55
72
72
dB
dB
V
S
OUT
L
V = ±5V, V
= ±2V, R = 150Ω
S
OUT
L
R
OL
Transresistance, ∆V /∆I
–
V = ±15V, V
= ±10V, R = 1k
●
●
100
100
270
240
kΩ
kΩ
OUT IN
S
OUT
L
V = ±5V, V
= ±2V, R = 150Ω
S
OUT
L
V
Maximum Output Voltage Swing
V = ±15V, R = 400Ω, T = 25°C
±12
±10
±3
±13.5
V
V
V
V
OUT
S
L
A
●
●
V = ±5V, R = 150Ω, T = 25°C
±3.7
S
L
A
±2.5
I
I
Maximum Output Current
Supply Current (Note 3)
R = 0Ω, T = 25°C
30
60
10
mA
mA
mA
OUT
S
L
A
V = ±15V, V
= 0V, T = 25°C
15.0
17.5
S
OUT
A
●
Positive Supply Current, Shutdown
V = ±15V, Pin 8 Voltage = 0V, T = 25°C
120
300
500
300
10
µA
µA
µA
µA
V/µs
ns
MHz
ns
S
A
●
●
I
Shutdown Pin Current (Note 4)
Output Leakage Current, Shutdown
Slew Rate (Notes 5 and 6)
V = ±15V
8
S
V = ±15V, Pin 8 Voltage = 0V, T = 25°C
S
A
SR
t , t
T = 25°C
500
1100
8.7
140
3.3
3.4
5
A
Rise and Fall Time, V
= 1V
V = ±5V, R = 1k, R = 1k, R = 150Ω
S F G L
r
f
OUT
P-P
BW
t , t
Small-Signal Bandwidth
Small-Signal Rise and Fall Time
Propagation Delay
Small-Signal Overshoot
Settling Time
V = ±15V, R = 1k, R = 1k, R = 150Ω
S
F
G
L
V = ±15V, R = 1k, R = 1k, R = 100Ω
S F G L
r
f
V = ±15V, R = 1k, R = 1k, R = 100Ω
ns
%
ns
S
F
G
L
V = ±15V, R = 1k, R = 1k, R = 100Ω
S
F
G
L
t
0.1%, V
= 10V, R = 1k, R = 1k, R = 1k
50
S
OUT
F
G
L
Differential Gain (Note 7)
V = ±15V, R = 1k, R = 1k, R = 150Ω
0.014
0.010
%
%
S
F
G
L
V = ±15V, R = 1k, R = 1k, R = 1k
S
F
G
L
Differential Phase (Note 7)
V = ±15V, R = 1k, R = 1k, R = 150Ω
0.010
0.013
DEG
DEG
S
F
G
L
V = ±15V, R = 1k, R = 1k, R = 1k
S
F
G
L
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 4: Ramp Pin 8 voltage down from 15V while measuring I . When I
drops to less than 0.5mA, measure Pin 8 current.
S
S
Note 2: A heat sink may be required depending on the power supply
voltage.
Note 5: Slew rate is measured at ±5V on a ±10V output signal while
operating on ±15V supplies with R = 2k, R = 220Ω and R = 400Ω.
F G L
Note 3: The supply current of the LT1227 has a negative temperature
coefficient. For more information, see Typical Performance Characteristics
curves.
Note 6: AC parameters are 100% tested on the ceramic and plastic DIP
package parts (J and N suffix) and are sample tested on every lot of the SO
packaged parts (S suffix).
Note 7: NTSC composite video with an output level of 2V.
3
LT1227
TYPICAL PERFOR A CE CHARACTERISTICS
U W
Voltage Gain and Phase vs
Frequency, Gain = 6dB
–3dB Bandwidth vs Supply
–3dB Bandwidth vs Supply
Voltage, Gain = 2, RL = 1k
Voltage, Gain = 2, RL = 100Ω
180
180
10
9
0
PEAKING ≤ 0.5dB
PEAKING ≤ 5dB
PHASE
PEAKING ≤ 0.5dB
PEAKING ≤ 5dB
45
90
135
160
140
120
100
80
160
140
120
100
80
8
R = 750Ω
F
R = 500Ω
F
7
R = 750Ω
F
R = 2k
F
6
5
180
225
GAIN
R = 1k
F
R = 1.5k
F
R = 1k
F
4
3
2
1
0
60
60
40
40
V
R
R
= ±15V
= 100Ω
= 910Ω
S
L
F
R = 2k
F
20
20
0
0
0
2
4
6
8
10 12 14 16 18
14
0
2
4
6
8
10 12
16 18
0.1
1
10
100
SUPPLY VOLTAGE (±V)
SUPPLY VOLTAGE (±V)
FREQUENCY (MHz)
LT1227 • TPC01
LT1227 • TPC02
LT1227 • TPC03
–3dB Bandwidth vs Supply
Voltage Gain and Phase vs
Frequency, Gain = 20dB
–3dB Bandwidth vs Supply
Voltage, Gain = 10, RL = 100Ω
Voltage, Gain = 10, RL = 1k
180
180
24
23
22
21
0
PHASE
PEAKING ≤ 0.5dB
PEAKING ≤ 5dB
PEAKING ≤ 0.5dB
PEAKING ≤ 5dB
45
90
135
160
140
120
100
80
160
140
120
100
80
R = 500Ω
F
20
19
180
225
R = 500Ω
F
GAIN
R = 250Ω
F
R = 750Ω
F
R = 750Ω
F
18
17
16
15
14
R = 1k
F
60
60
R = 1k
F
40
40
V
R
R
= ±15V
= 100Ω
= 825Ω
S
L
F
R = 2k
F
20
20
R = 2k
F
0
0
0
2
4
6
8
10 12 14 16 18
SUPPLY VOLTAGE (±V)
0
2
4
6
8
10 12 14 16 18
SUPPLY VOLTAGE (±V)
0.1
1
10
100
FREQUENCY (MHz)
LT1227 • TPC06
LT1227 • TPC04
LT1227 • TPC05
Voltage Gain and Phase vs
Frequency, Gain = 40dB
–3dB Bandwidth vs Supply
Voltage, Gain = 100, RL = 100Ω
–3dB Bandwidth vs Supply
Voltage, Gain = 100, RL = 1k
18
18
44
43
42
41
0
PHASE
45
90
135
R = 500Ω
F
16
14
12
10
8
16
14
12
10
8
R = 1k
F
R = 500Ω
F
R = 1k
F
R = 2k
F
40
39
180
225
GAIN
R = 2k
F
38
37
36
35
34
6
6
4
4
V
R
R
= ±15V
= 100Ω
= 500Ω
S
L
F
2
2
0
0
0
2
4
6
8
10 12 14 16 18
0
2
4
6
8
10 12 14 16 18
0.1
1
10
100
SUPPLY VOLTAGE (±V)
SUPPLY VOLTAGE (±V)
FREQUENCY (MHz)
LT1227 • TPC07
LT1227 • TPC09
LT1227 • TPC08
4
LT1227
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Maximum Capacitive Load
vs Feedback Resistor
Total Harmonic Distortion
vs Frequency
Maximum Undistorted Output
vs Frequency
0.1
10000
1000
100
25
20
R
= 1k
V
= ±15V
= 400Ω
G
V
R
R
= ±15V
= 1k
= 1k
L
S
L
F
S
L
F
PEAKING ≤ 5dB
R
GAIN = 2
R = R = 1k
V
S
= ±5V
A
A
= +10
= –1
V
V
15
10
5
V
S
= ±15V
0.01
V
= 7V
= 1V
O
RMS
A
= +1
V
A
= +2
10
V
V
O
RMS
0.001
0
1
10
100
1k
FREQUENCY (Hz)
10k
100k
1
10
FREQUENCY (MHz)
100
0
1
2
3
FEEDBACK RESISTOR (kΩ)
LT1127 • TPC12
LT1227 • TPC11
LT1227 • TPC10
Input Common Mode Limit
vs Temperature
Output Short-Circuit Current
vs Junction Temperature
Output Saturation Voltage
vs Temperature
+
+
V
70
60
V
R
= ∞
L
–0.5
–1.0
–1.5
–2.0
±2V ≤ V ≤ ±18V
S
+
–0.5
–1.0
V
= 2V TO 18V
50
40
2.0
1.5
1.0
0.5
1.0
0.5
–
V
= –2V TO –18V
–
–
V
30
V
50
100 125
–50 –25
0
25
75
–50
0
25
50
75 100 125
–50
–25
0
25
50 75 100 125 150 175
TEMPERATURE (°C)
–25
TEMPERATURE (°C)
TEMPERATURE (°C)
LT1227 • TPC14
LT1227 • TPC15
LT1227 • TPC13
Power Supply Rejection
vs Frequency
Spot Noise Voltage and Current
vs Frequency
Output Impedance vs Frequency
100
10
1
100
10
80
60
40
V
R
= ±15V
= 100Ω
G
V
S
= ±15V
S
L
F
R = R = 1k
–i
n
POSITIVE
R = R = 2k
F
G
1
0.1
NEGATIVE
R = R = 1k
F
G
e
n
20
0
0.01
+i
n
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
10k
100k
1M
FREQUENCY (Hz)
10M
100M
LT1227 • TPC16
LT1227 • TPC17
LT1227 • TPC18
5
LT1227
TYPICAL PERFOR A CE CHARACTERISTICS
U W
Settling Time to 1mV
vs Output Step
Settling Time to 10mV
vs Output Step
Supply Current vs Supply Voltage
14
13
12
11
10
9
10
8
10
8
V
= ±15V
G
V
= ±15V
G
S
F
S
F
R
= R = 1k
R = R = 1k
6
6
–55°C
25°C
4
4
NONINVERTING
INVERTING
2
2
NONINVERTING
INVERTING
0
0
8
–2
–4
–6
–8
–10
–2
–4
–6
–8
–10
125°C
175°C
7
6
5
4
0
2
4
6
8
10 12 14 16 18
0
20
40
60
80
100
0
4
8
12
16
20
SUPPLY VOLTAGE (±V)
SETTLING TIME (ns)
SETTLING TIME (µs)
LT1227 • TPC21
LT1227 • TPC19
LT1227 • TPC20
Output Impedance in Shutdown
vs Frequency
Differential Phase vs Frequency
Differential Gain vs Frequency
100
10
1
0
0
0.01
0.02
0.03
0.04
0.05
0.06
V
A
= ±15V
S
V
F
(V ) = 0.5V
O DC
= 1
0.05
0.10
1.0V
1.5V
2.0V
R = 1.5k
(V ) = 0.5V
O DC
0.15
0.20
0.25
0.30
1.0V
2.0V
V
A
= ±15V
= 2
V
A
= ±15V
= 2
= 1k
R = 1k
= 1k
S
V
L
F
G
S
V
L
F
G
R
= 1k
R
R = 1k
R
= 1k
R
0.1
100k
1M
10M
100M
100k
1M
10M
100M
100k
1M
10M
100M
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
LT1227 • TPC22
LT1227 • TPC23
LT1227 • TPC24
2nd and 3rd Harmonic Distortion
vs Frequency
3rd Order Intercept vs Frequency
Test Circuit for 3rd Order Intercept
–20
–30
45
40
V
V
R
R
A
= ±15V
S
O
L
F
V
= ±15V
= 100Ω
S
L
F
G
= 2V
P-P
R
+
= 100Ω
= 820Ω
= 10dB
R = 680Ω
R
50Ω
= 75Ω
P
O
LT1227
V
35
30
–
–40
–50
–60
–70
2ND
680Ω
3RD
25
20
15
50Ω
75Ω
MEASURE INTERCEPT AT P
O
1227 TC
1
10
FREQUENCY (MHz)
100
0
10
20
30
40
50
60
FREQUENCY (MHz)
LT1227 • TPC25
LT1227 • TPC26
6
LT1227
W
W
SI PLIFIED SCHE ATIC
+
V
7
14k
1
NULL
5
NULL
CURRENT
SOURCE
BIAS
8
S/D
–IN
3
2
6
V
+IN
OUT
–
V
4
1227 SS
O U
S
W
U
PPLICATI
A
I FOR ATIO
The LT1227 is a very fast current feedback amplifier.
Because it is a current feedback amplifier, the bandwidth
is maintained over a wide range of voltage gains. The
amplifierisdesignedtodrivelowimpedanceloadssuchas
cables with excellent linearity at high frequencies.
5dB of peaking. The curves stop where the response has
more than 5dB of peaking.
At a gain of two, on ±15V supplies with a 1k feedback
resistor, the bandwidth into a light load is over 140MHz,
but into a heavy load the bandwidth reduces to 120MHz.
The loading has this effect because there is a mild reso-
nance in the output stage that enhances the bandwidth at
light loads but has its Q reduced by the heavy load. This
enhancement is only useful at low gain settlings; at a gain
of ten it does not boost the bandwidth. At unity gain, the
enhancement is so effective the value of the feedback
resistor has very little effect. At very high closed-loop
gains, the bandwidth is limited by the gain bandwidth
product of about 1GHz. The curves show that the band-
widthataclosed-loopgainof100is12MHz,onlyonetenth
what it is at a gain of two.
Feedback Resistor Selection
The small-signal bandwidth of the LT1227 is set by the
external feedback resistors and the internal junction ca-
pacitors. As a result, the bandwidth is a function of the
supply voltage, the value of the feedback resistor, the
closed-loop gain and load resistor. The characteristic
curves of Bandwidth vs Supply Voltage show the effect of
a heavy load (100Ω) and a light load (1k). These curves
use a solid line when the response has less than 0.5dB of
peaking and a dashed line when the response has 0.5dB to
7
LT1227
PPLICATI
O U
W
U
A
S I FOR ATIO
Small-Signal Rise Time, AV = +2
and inverting input bias current will change. The offset
voltage changes about 500µV per volt of supply mis-
match. The inverting bias current can change as much as
5.0µA per volt of supply mismatch, though typically the
change is less than 0.5µA per volt.
Slew Rate
VOUT
The slew rate of a current feedback amplifier is not
independent of the amplifier gain configuration the way
slewrateisinatraditionalopamp.Thisisbecauseboththe
inputstageandtheoutputstagehaveslewratelimitations.
In the inverting mode, and for higher gains in the
noninverting mode, the signal amplitude between the
input pins is small and the overall slew rate is that of the
output stage. For gains less than ten in the noninverting
mode, the overall slew rate is limited by the input stage.
AI01
RF = 1k, RG= 1k, RL = 100Ω
Capacitance on the Inverting Input
Current feedback amplifiers require resistive feedback
from the output to the inverting input for stable operation.
Take care to minimize the stray capacitance between the
output and the inverting input. Capacitance on the invert-
ing input to ground will cause peaking in the frequency
response (and overshoot in the transient response), but it
does not degrade the stability of the amplifier.
The input stage slew rate of the LT1227 is approximately
125V/µs and is set by internal currents and capacitances.
The output slew rate is set by the value of the feedback
resistors and the internal capacitances. At a gain of ten
with a 1k feedback resistor and ±15V supplies, the output
slew rate is typically 1100V/µs. Larger feedback resistors
will reduce the slew rate as will lower supply voltages,
similar to the way the bandwidth is reduced.
Capacitive Loads
The graph of Maximum Undistorted Output vs Frequency
relates the slew rate limitations to sinusoidal inputs for
various gain configurations.
The LT1227 can drive capacitive loads directly when the
proper value of feedback resistor is used. The graph of
Maximum Capacitive Load vs Feedback Resistor should
be used to select the appropriate value. The value shown
isfor5dBpeakingwhendrivinga1kloadatagainof2.This
is a worst case condition, the amplifier is more stable at
higher gains and driving heavier loads. Alternatively, a
small resistor (10Ω to 20Ω) can be put in series with the
output to isolate the capacitive load from the amplifier
output. This has the advantage that the amplifier band-
width is only reduced when the capacitive load is present
and the disadvantage that the gain is a function of the load
resistance.
Large-Signal Transient Response, AV = +10
VOUT
Power Supplies
The LT1227 will operate from single or split supplies from
±2V (4V total) to ±15V (30V total). It is not necessary to
use equal value split supplies, however the offset voltage
AI02
RF = 910Ω, RG= 100Ω, RL = 400Ω
8
LT1227
O U
W
U
PPLICATI
S I FOR ATIO
A
Large-Signal Transient Response, AV = +2
Shutdown
The LT1227 has a high impedance, low supply current
mode which is controlled by Pin 8. In the shutdown mode,
the output looks like a 12pF capacitor and the supply
current drops to approximately the Pin 8 current. The
shutdown pin is referenced to the positive supply through
an internal pullup circuit (see the simplified schematic).
Pulling a current of greater than 50µA from Pin 8 will put
the device into the shutdown mode. An easy way to force
shutdown is to ground Pin 8, using open drain (collector)
logic. Because the pin is referenced to the positive supply,
the logic used should have a breakdown voltage of greater
than the positive supply voltage. No other circuitry is
necessary as an internal JFET limits the Pin 8 current to
about 100µA. When Pin 8 is open, the LT1227 operates
normally.
VOUT
AI03
RF = 1k, RG= 1k, RL = 400Ω
Large-Signal Transient Response, AV = –2
Differential Input Signal Swing
The differential input swing is limited to about ±6V by an
ESD protection device connected between the inputs. In
normal operation, the differential voltage between the
input pins is small, so this clamp has no effect; however,
in the shutdown mode, the differential swing can be the
same as the input swing. The clamp voltage will then set
the maximum allowable input voltage. To allow for some
margin, it is recommended that the input signal be less
than ±5V when the device is shutdown.
VOUT
AI04
R
F = 1k, RG= 510Ω, RL = 400Ω
Offset Adjust
Pins1and5areprovidedforoffsetnulling. Asmallcurrent
to V+ or ground will compensate for DC offsets in the
device. The pins are referenced to the positive supply (see
the simplified schematic) and should be left open if un-
used. The offset adjust pins act primarily on the inverting
input bias current. A 10k pot connected to Pins 1 and 5
with the wiper connected to V+ will null out the bias
current, but will not affect the offset voltage much. Since
the output offset is
Settling Time
The characteristic curves show that the LT1227 amplifier
settlestowithin10mVoffinalvaluein40nsto55nsforany
output step up to 10V. The curve of settling to 1mV of final
value shows that there is a slower thermal contribution up
to 20µs. The thermal settling component comes from the
output and the input stage. The output contributes just
under 1mV per volt of output change and the input
contributes 300µV per volt of input change. Fortunately
the input thermal tends to cancel the output thermal. For
this reason the noninverting gain of two configuration
settles faster than the inverting gain of one.
VO AV • VOS + (IIN ) • RF
–
athighergains(AV >5),theVOS termwilldominate.Tonull
out the VOS term, use a 10k pot between Pins 1 and 5 with
a 150k resistor from the wiper to ground for 15V split
supplies, 47k for 5V split supplies.
9
LT1227
U
O
TYPICAL APPLICATI S
MUX Amplifier
MUX Amplifier
15V
The shutdown function can be effectively used to con-
struct a MUX amplifier. A two-channel version is shown,
but more inputs could be added with suitable logic. By
configuring each amplifier as a unity-gain follower, there
is no loading by the feedback network when the amplifier
is off. The open drains of the 74C906 buffers are used to
interface the 5V logic to the shutdown pin. Feedthrough
from the unselected input to the output is –70dB at
10MHz. The differential voltage between MUX inputs VIN1
and VIN2 appears across the inputs of the shutdown
device, this voltage should be less than ±5V to avoid
turning on the clamp diodes discussed previously. If the
inputs are sinusoidal having a zero DC level, this implies
that the amplitude of each input should be less than
5VP-P. The output impedance of the off amplifier remains
high until the output level exceeds approximately 6VP-P at
10MHz,thissetsthemaximumusableoutputlevel.Switch-
ing time between inputs is about 4µs without an external
pullup. Adding a 10k pullup resistor from each shutdown
pin to V+ will reduce the switching time to 2µs but will
increasethepositivesupplycurrentinshutdownby1.5mA.
V
+
IN1
LT1227
S/D
V
OUT
–
–15V
1.5k
V
OUT
= 1
V
IN
5V
74C906
15V
V
+
IN2
LT1227
S/D
–
–15V
1.5k
5V
5V
INPUT
SELECT
74C906
74HC04
1227 TA04
MUX Output
MUX Input Crosstalk vs Frequency
–40
–50
VOUT
–60
–70
–80
–90
INPUT
SELECT
TA03
1
10
100
VIN1 = 1VP-P, VIN2 = 0V
FREQUENCY (MHz)
LT1227 TA05
10
LT1227
U
PACKAGE DESCRIPTIO
J8 Package
8-Lead CERDIP (Narrow .300 Inch, Hermetic)
(Reference LTC DWG # 05-08-1110)
0.405
(10.287)
MAX
0.005
(0.127)
MIN
0.300 BSC
(0.762 BSC)
CORNER LEADS OPTION
(4 PLCS)
6
5
4
8
7
0.015 – 0.060
(0.381 – 1.524)
0.023 – 0.045
(0.584 – 1.143)
HALF LEAD
OPTION
0.025
(0.635)
RAD TYP
0.220 – 0.310
(5.588 – 7.874)
0.008 – 0.018
(0.203 – 0.457)
0° – 15°
0.045 – 0.068
(1.143 – 1.727)
FULL LEAD
OPTION
1
2
3
0.200
(5.080)
MAX
0.045 – 0.065
(1.143 – 1.651)
0.125
3.175
MIN
NOTE: LEAD DIMENSIONS APPLY TO SOLDER
DIP/PLATE OR TIN PLATE LEADS
0.014 – 0.026
(0.360 – 0.660)
0.100
(2.54)
BSC
J8 1298
OBSOLETE PACKAGE
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
0.400*
(10.160)
MAX
0.130 ± 0.005
0.300 – 0.325
0.045 – 0.065
(3.302 ± 0.127)
(1.143 – 1.651)
(7.620 – 8.255)
8
1
7
6
5
0.065
(1.651)
TYP
0.255 ± 0.015*
(6.477 ± 0.381)
0.009 – 0.015
(0.229 – 0.381)
0.125
0.020
(0.508)
MIN
(3.175)
MIN
+0.035
–0.015
2
4
3
0.325
0.018 ± 0.003
0.100
(2.54)
BSC
+0.889
8.255
(0.457 ± 0.076)
(
)
N8 1098
–0.381
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
0.010 – 0.020
(0.254 – 0.508)
7
5
8
6
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
0.016 – 0.050
(0.406 – 1.270)
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
SO8 1298
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
1
2
3
4
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
11
LT1227
U
O
TYPICAL APPLICATI S
Single Supply AC-Coupled
Amplifier Noninverting
Single Supply AC-Coupled
Amplifier Inverting
3.58MHz Oscillator
15V
5V
5V
1N4148
100k
4.7µF
4.7µF
2N3904
510Ω
A
V
=
≈
10
R
+ 51Ω
100pF
S
75pF
10k
10k
22µF
10k
10k
BW = 14Hz to 60MHz
3.579545MHz
1k
V
IN
+
–
+
–
68pF
150k
+
V
LT1227
OUT
V
LT1227
OUT
2.2µF
15V
–
51Ω
220µF
V
LT1227
220µF
OUT
510Ω
51Ω
R
S
51Ω
510Ω
+
V
IN
1227 TA09
A
= 11
V
BW = 14Hz to 60MHz
1227 TA08
–15V
1227 TA10
Buffer with DC Nulling Loop
CMOS Logic to Shutdown Interface
Optional Offset Nulling Circuit
+
V
R
180Ω
10k
180Ω
10k
NULL
+
15V
7
+
V
10k
7
3
3
2
0.1µF
+
1
5
6
3
2
6
V
LT1227
+
–
LT1227
IN
1
6
2
8
5
R
NULL
R
NULL
= 47k FOR V = ±5V
V
OUT
LT1227
–
S
–
10k
= 150k FOR V = ±15V
4
–
S
4
1227 TA12
–15V
5V
V
1.5k
10k
2N3904
100k
0.01µF
1227 TA11
+
–
LT1097
100k
0.01µF
1227 TA07
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1395/LT1396/LT1397 Single/Dual/Quad 400MHz Current Feedback Amplifier
Miniature Packages: SOT-23, MSOP-8, SSOP-16
1227fb LT/CP 1001 1.5K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1994
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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