LINER LT1187C Low power video difference amplifier Datasheet

LT1187
Low Power
Video Difference Amplifier
U
DESCRIPTIO
FEATURES
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Differential or Single-Ended Gain Block (Adjustable)
–3dB Bandwidth, AV = ±2
50MHz
Slew Rate
165V/µs
Low Supply Current
13mA
Output Current
± 20mA
CMRR at 10MHz
40dB
LT1193 Pin Compatible
Low Cost
Single 5V Operation
Drives Cables Directly
Output Shutdown
UO
APPLICATI
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The LT1187’s high slew rate, 165V/µs, wide bandwidth,
50MHz, and ±20mA output current require only 13mA of
supply current. The shutdown feature reduces the power
dissipation to a mere 15mW, and allows multiple amplifiers to drive the same cable.
The LT1187 is a low power version of the popular LT1193,
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
Video Signal Processing
Cable Drivers
Tape and Disc Drive Systems
UO
■
S
The LT1187 is a difference amplifier optimized for operation on ±5V, or a single 5V supply, and gain ≥2. This
versatile amplifier features uncommitted high input impedance (+) 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.
TYPICAL APPLICATI
Cable Sense Amplifier for Loop Through Connections
with DC Adjust
Closed-Loop Gain vs Frequency
40
V IN
30
CABLE
2
VDC
1
8
+
7
–
LT1187
+
–
6
VOUT
4
–5V
1k
VOLTAGE GAIN (dB)
5V
3
VS = ±5V
RL = 1k
20
10
0
1k
–10
0.1
LT1187 • TA01
1
10
FREQUENCY (MHz)
100
LT1187 • TA02
1
LT1187
W
U
U
W W
W
AXI U
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ABSOLUTE
PACKAGE/ORDER I FOR ATIO
RATI GS
Total Supply Voltage (V + to V –) ............................. 18V
Differential Input Voltage ........................................ ±6V
Input Voltage .......................................................... ±VS
Output Short Circuit Duration (Note 1) ........ Continuous
Operating Temperature Range
LT1187M ..................................... – 55°C to 150°C
LT1187C............................................. 0°C to 70°C
Junction Temperature (Note 2)
Plastic Package (CN8,CS8) ......................... 150°C
Ceramic Package (CJ8,MJ8) ....................... 175°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec.)................ 300°C
ORDER PART
NUMBER
TOP VIEW
+/REF
1
8
–/FB
–IN
2
7
V+
+IN
3
6
OUT
V–
4
5
S/D
LT1187MJ8
LT1187CJ8
LT1187CN8
LT1187CS8
J8 PACKAGE
N8 PACKAGE
8-LEAD HERMETIC DIP 8-LEAD PLASTIC DIP
S8 PACKAGE
8-LEAD PLASTIC SOIC
S8 PART MARKING
LT1187 • POI01
TJMAX = 175°C, θJA = 100°C/W (J8)
TJMAX = 150°C, θJA = 100°C/W (N8)
TJMAX = 150°C, θJA = 150°C/W (S8)
1187
Consult factory for Industrial grade parts.
+
– 5V ELECTRICAL CHARACTERISTICS
TA = 25°C, (Note 3)
VS = ±5V, VREF = 0V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open.
PARAMETER
Input Offset Voltage
CONDITIONS
Either Input, (Note 4)
SOIC Package
IOS
IB
Input Offset Current
Input Bias Current
Either Input
Either Input
en
Input Noise Voltage
fO = 10kHz
65
nV/√Hz
in
Input Noise Current
fO = 10kHz
1.5
pA/√Hz
RIN
Input Resistance
Differential
100
kΩ
CIN
Input Capacitance
Either Input
2.0
pF
VIN LIM
Input Voltage Limit
(Note 5)
±380
mV
Input Voltage Range
MIN
LT1187M/C
TYP
MAX
2.0
10
2.0
11
SYMBOL
VOS
0.2
±0.5
–2.5
CMRR
PSRR
Common-Mode Rejection Ratio
Power Supply Rejection Ratio
VCM = –2.5V to 3.5V
VS = ±2.375V to ±8V
VOUT
Output Voltage Swing
1.0
±2.0
3.5
UNITS
mV
mV
µA
µA
V
70
70
100
85
dB
dB
VS = ±5V, RL = 1k, AV = 50
±3.8
±4.0
V
VS = ±8V, RL = 1k, AV = 50
±6.7
±7.0
VS = ±8V, RL = 300Ω, AV = 50, (Note 3)
±6.4
± 6.8
GE
Gain Error
VO = ±1V, AV = 10, RL = 1k
SR
Slew Rate
(Note 6, 10)
FPBW
Full Power Bandwidth
VO = 1VP-P, (Note 7)
BW
tr, tf
Small Signal Bandwidth
Rise Time, Fall Time
AV = 10
AV = 50, VO = ±1.5V, 20% to 80% (Note 10)
tPD
Propagation Delay
RL= 1k, VO = ±125mV, 50% to 50%
Overshoot
VO = ± 50mV
0
%
Settling Time
3V Step, 0.1%, (Note 8)
100
ns
Diff AV
Differential Gain
RL = 1k, AV = 4, (Note 9)
0.6
%
Diff Ph
Differential Phase
RL = 1k, AV = 4, (Note 9)
0.8
DEGP-P
IS
Supply Current
ts
Shutdown Supply Current
2
Pin 5 at V –
0.2
100
150
1.0
%
165
V/µs
53
MHz
5.7
230
325
26
MHz
ns
ns
13
16
mA
0.8
1.5
mA
LT1187
+
– 5V ELECTRICAL CHARACTERISTICS
TA = 25°C, (Note 3)
VS = ±5V, VREF = 0V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open.
SYMBOL
PARAMETER
CONDITIONS
Shutdown Pin Current
Pin 5 at V –
tON
Turn On Time
tOFF
Turn Off Time
Pin 5 from V – to Ground, RL = 1k
Pin 5 from Ground to V –, RL = 1k
IS/D
MIN
LT1187M/C
TYP
MAX
5
25
UNITS
µA
500
ns
600
ns
5V
CHARACTERISTICS
ELECTRICAL
+
–
TA = 25°C, (Note 3)
VS = 5V, VS = 0V, VREF = 2.5V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to VREF, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5
open.
SYMBOL
PARAMETER
CONDITIONS
VOS
Input Offset Voltage
Either Input, (Note 4)
SOIC Package
IOS
Input Offset Current
Either Input
IB
Input Bias Current
Either Input
MIN
LT1187M/C
TYP
MAX
2.0
2.0
Input Voltage Range
mV
mV
0.2
1.0
µA
± 0.5
± 2.0
µA
3.5
V
2.0
CMRR
Common-Mode Rejection Ratio
VCM = 2.0V to 3.5V
VOUT
Output Voltage Swing
RL = 300Ω to Ground
(Note 3)
VOUT High
UNITS
10
12
70
100
dB
3.6
4.0
V
VOUT Low
0.15
0.4
SR
Slew Rate
VO = 1.5V to 3.5V
130
V/µs
BW
Small-Signal Bandwidth
AV = 10
5.3
MHz
IS
Supply Current
IS/D
–
Shutdown Supply Current
Pin 5 at V
Shutdown Pin Current
Pin 5 at V –
12
15
mA
0.8
1.5
mA
5
25
µA
+
– 5V ELECTRICAL CHARACTERISTICS
–55°C ≤ TA ≤ 125°C, (Note 3)
VS = ±5V, VREF = 0V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open.
MIN
LT1187M
TYP
MAX
SYMBOL
PARAMETER
CONDITIONS
VOS
Input Offset Voltage
Either Input, (Note 4)
∆VOS /∆T
Input VOS Drift
IOS
Input Offset Current
Either Input
0.2
1.5
µA
IB
Input Bias Current
Either Input
± 0.5
±3.5
µA
2.0
15
–2.5
mV
µV/°C
8.0
Input Voltage Range
UNITS
3.5
V
CMRR
Common-Mode Rejection Ratio
VCM = –2.5V to 3.5V
70
100
dB
PSRR
Power Supply Rejection Ratio
VS = ±2.375V to ±8V
60
85
dB
VOUT
Output Voltage Swing
VS = ±5V, RL = 1k, AV = 50
±3.7
± 4.0
V
VS = ±8V, RL = 1k, AV = 50
±6.6
±7.0
VS = ±8V, RL = 300Ω, AV = 50, (Note 3)
±6.4
± 6.8
GE
Gain Error
IS
Supply Current
Shutdown Supply Current
IS/D
Shutdown Pin Current
VO = ±1V, AV = 10, RL = 1k
0.2
1.2
%
13
17
mA
Pin 5 at V –, (Note 11)
0.8
1.5
mA
–
5
25
µA
Pin 5 at V
3
LT1187
+
ELECTRICAL CHARACTERISTICS 0°C ≤ TA ≤ 70°C, (Note 3)
–V 5V
= ±5V, V = 0V, R = 900Ω from pins 6 to 8, R = 100Ω from pin 8 to ground, R = R
S
REF
FB1
FB2
L
SYMBOL
PARAMETER
CONDITIONS
VOS
Input Offset Voltage
Either Input, (Note 4)
∆VOS /∆T
Input VOS Drift
IOS
Input Offset Current
Either Input
IB
Input Bias Current
Either Input
Common-Mode Rejection Ratio
+ RFB2 = 1k, CL ≤ 10pF, pin 5 open.
MIN
LT1187C
TYP
MAX
2.0
12
70
mV
0.2
1.5
µA
± 0.5
±3.5
µA
3.5
V
– 2.5
VCM = –2.5V to 3.5V
UNITS
µV/°C
9.0
Input Voltage Range
CMRR
FB1
100
dB
PSRR
Power Supply Rejection Ratio
VS = ±2.375V to ±8V
65
85
dB
VOUT
Output Voltage Swing
VS = ±5V, RL = 1k, AV = 50
±3.7
±4.0
V
VS = ±8V, RL = 1k, AV = 50
±6.6
±7.0
VS = ±8V, RL = 300Ω, AV = 50, (Note 3)
±6.4
± 6.8
GE
Gain Error
IS
Supply Current
IS/D
VO = ±1V, AV = 10, RL = 1k
–
Shutdown Supply Current
Pin 5 at V , (Note 11)
Shutdown Pin Current
Pin 5 at V –
0.2
1.0
%
13
17
mA
0.8
1.5
mA
5
25
µA
CHARACTERISTICS
ELECTRICAL
5V
+
–
0°C ≤ TA ≤ 70°C, (Note 3)
VS = 5V, VS = 0V, VREF = 2.5V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to VREF, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open.
SYMBOL
PARAMETER
CONDITIONS
VOS
Input Offset Voltage
Either Input, (Note 4)
SOIC Package
∆VOS/∆T
Input VOS Drift
IOS
Input Offset Current
Either Input
IB
Input Bias Current
Either Input
MIN
2.0
2.0
Common-Mode Rejection Ratio
VCM = 2.0V to 3.5V
VOUT
Output Voltage Swing
RL = 300Ω to Ground
VOUT High
(Note 3)
VOUT Low
Supply Current
Shutdown Supply Current
Pin 5 at V –, (Note 11)
Shutdown Pin Current
Pin 5 at V –
Note 1: A heat sink may be required to keep the junction temperature below
absolute maximum when the output is shorted continuously.
Note 2: TJ is calculated from the ambient temperature T A and power dissipation
PD according to the following formulas:
LT1187MJ8,LT1187CJ8: TJ = TA + (PD × 100°C/W)
LT1187CN8:
TJ = TA + (PD × 100°C/W)
LT1187CS8:
TJ = TA + (PD × 150°C/W)
Note 3: When RL = 1k is specified, the load resistor is RFB1 + RFB2, but when
RL = 300Ω is specified, then an additional 430Ω is added to the output such
that (RFB1 + RFB2) in parallel with 430Ω is RL = 300Ω.
Note 4: VOS measured at the output (pin 6) is the contribution from both input
pair, and is input referred.
Note 5: VIN LIM is the maximum voltage between –V IN and +VIN (pin 2 and
pin 3) for which the output can respond.
4
UNITS
mV
mV
µV/°C
0.2
1.5
µA
± 0.5
± 3.5
µA
3.5
V
2.0
CMRR
IS/D
12.0
13.0
9.0
Input Voltage Range
IS
LT1187C
TYP
MAX
70
100
dB
3.5
4.0
V
0.15
0.4
12
16
mA
0.8
1.5
mA
5
25
µA
Note 6: Slew rate is measured between ±0.5V on the output, with a VIN step
of ±0.75V, AV = 3 and RL = 1k.
Note 7: Full power bandwidth is calculated from the slew rate measurement:
FPBW = SR/2πVp.
Note 8: Settling time measurement techniques are shown in “Take the
Guesswork Out of Settling Time Measurements,” EDN, September 19, 1985.
Note 9: NTSC (3.58MHz).
Note 10: 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).
Note 11: See Application section for shutdown at elevated temperatures. Do
not operate shutdown above T J > 125°C.
LT1187
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TYPICAL PERFOR A CE CHARACTERISTICS
Input Bias Current vs
Common-Mode Voltage
Common-Mode Voltage vs
Temperature
Input Bias Current vs Temperature
V+
100
3.0
VS = ±5V
1.5
–55°C
1.0
0.5
25°C
0
+IB
0
–100
COMMON-MODE RANGE (V)
INPUT BIAS CURRENT (nA)
–IB
IOS
–200
–300
125°C
–5 –4 –3 –2 –1 0 1 2 3
COMMON-MODE VOLTAGE (V)
4
– 400
–50
5
–25
0
25
75
50
TEMPERATURE (°C)
V + = –1.8V TO –9V
1.0
400
300
200
100
0
1k
10k
FREQUENCY (Hz)
8
6
4
25°C
12
125°C
10
2
0
Shutdown Supply Current vs
Temperature
100
1k
10k
FREQUENCY (Hz)
8
100k
Open-Loop Gain vs Temperature
VS = ±5V
VOUT = ±2V
AV = 10
RL = 1k
VS = ±5V
2
GAIN ERROR (%)
–0.05
VS/D = –VEE + 0.2V
10
8
5
VS/D = –VEE + 0.4V
4
6
8
±SUPPLY VOLTAGE (V)
LT1187 • TPC06
Gain Error vs Temperature
3
2
0
0
VS/D = –VEE + 0.6V
– 55°C
14
LT1187 • TPC05
6
125
Supply Current vs Supply Voltage
VS = ±5V
TA = 25°C
RS = 100k
10
10
100k
100
16
SUPPLY CURRENT (mA)
VS = ±5V
TA = 25°C
RS = 0Ω
0
25
75
50
TEMPERATURE (°C)
LT1187 • TPC03
12
LT1187 • TPC04
SHUTDOWN SUPPLY CURRENT (mA)
2.0
1.5
Equivalent Input Noise Current vs
Frequency
EQUIVALENT INPUT NOISE CURRENT (pA/√Hz)
EQUIVALENT INPUT NOISE VOLTAGE (nV/√Hz)
600
4
–2.0
LT1187 • TPC02
Equivalent Input Noise Voltage vs
Frequency
100
–1.5
V–
– 50 –25
125
100
LT1187 • TPC01
500
–1.0
0.5
–0.5
VS = ±5V
VO = ±3V
OPEN-LOOP GAIN (kV/V)
INPUT BIAS CURRENT (µA)
2.0
10
V + = 1.8V TO 9V
–0.5
2.5
–0.10
–0.15
RL = 1k
6
4
RL = 500Ω
2
1
VS/D = –VEE
0
–50
–25
50
0
25
75
TEMPERATURE (°C)
100
125
LT1187 • TPC07
–0.20
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
LT1187 • TPC08
0
–50 –25
25
75
0
50
TEMPERATURE (°C)
100
125
LT1187 • TPC09
5
LT1187
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Open-Loop Voltage Gain vs
Load Resistance
Gain, Phase vs Frequency
100
80
40
40
GAIN
20
20
0
PHASE MARGIN (DEG)
60
60
0
–20
100k
16k
–20
1M
10M
FREQUENCY (Hz)
60
12k
8k
4k
TA = 25°C
50
TA = 125˚C
40
30
0
100
100M
TA = – 55°C
AV = 20dB
VS = ±5V
VO = ±3V
TA = +25˚C
GAIN BANDWIDTH PRODUCT (MHz)
PHASE
80
VOLTAGE GAIN (dB)
VS = ±5V
TA = 25°C
RL = 1k
OPEN-LOOP VOLTAGE GAIN (V/V)
100
Gain Bandwidth Product vs
Supply Voltage
1k
LOAD RESISTANCE (Ω)
10k
0
2
4
8
6
±SUPPLY VOLTAGE (V)
LT1187 • TPC11
LT1187 • TPC12
Gain Bandwidth Product and
Unity Gain Phase Margin vs
Temperature
65
55
UNITY GAIN
PHASE MARGIN
40
45
OUTPUT IMPEDANCE (Ω)
GAIN BANDWIDTH
PRODUCT
COMMON-MODE REJECTION RATIO (dB)
VS = ±5V
TA = 25°C
PHASE MARGIN (DEG)
10
AV = 10
1.0
AV = 2
30
–50
–25
25
75
0
50
TEMPERATURE (°C)
35
125
100
0.1
1k
10k
100k
1M
FREQUENCY (Hz)
LT1187 • TPC13
40
20
0
–20
1k
10k
1M
100k
FREQUENCY (Hz)
10M
100M
LT1187 • TPC16
OUTPUT SHORT CIRCUIT CURRENT (mA)
POWER SUPPLY REJECTION RATIO (dB)
+PSRR
–PSRR
50
40
1M
10M
FREQUENCY (Hz)
V+
– 0.7
VS = ± 5V
35
34
33
32
31
30
– 50
–25
50
0
25
75
TEMPERATURE (°C)
100
125
LT1187 • TPC17
100M
LT1187 • TPC15
36
60
60
30
100k
100M
Output Short Circuit Current vs
Temperature
80
VS = ±5V
TA = 25°C
VRIPPLE = ±300mV
VS = ±5V
TA = 25°C
RL = 1k
70
LT1187 • TPC14
Power Supply Rejection Ratio vs
Frequency
6
10M
OUTPUT SATURATION VOLTAGE (V)
GAIN BANDWIDTH PRODUCT (MHz)
80
100
VS = ±5V
RL = 1k
50
Common-Mode Rejection Ratio
vs Frequency
Output Impedance vs Frequency
60
10
± Output Swing vs Supply Voltage
–0.8
125°C
–0.9
25°C
–1.0
–1.1
0.5
–55°C
RL = 1k
±1.8V ≤ VS ≤ ±9V
0.4
125°C
25°C
0.3
–55°C
0.2
0.1
V– 0
2
4
6
8
±SUPPLY VOLTAGE (V)
10
LT1187 • TPC18
LT1187
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Output Voltage Swing vs
Load Resistance
250
4
VS = ±5V
TA = –55°C
3
SLEW RATE (V/µs)
TA = 25°C
TA = 125°C
1
–1
TA = 25°C
–3
200
+SLEW RATE
TA = –55°C
TA = 125°C
150
–50 –25
–5
100
LOAD RESISTANCE (Ω)
1000
VS = ±5V
TA = 25°C
RL = 1k
10mV
2
0
–2
10mV
–4
0
25
50
75
TEMPERATURE (°C)
100
125
40
50
60
70
80
SETTLING TIME (ns)
LT1187 • TPC20
LT1187 • TPC19
Harmonic Distortion vs
Output Voltage
90
100
LT1187 • TPC21
Large-Signal Transient Response
–30
VS = ±5V
TA = 25°C
RL = 1k
f = 1MHz
AV = 10
–35
DISTORTION (dBc)
10
–SLEW RATE
VS = ±5V
RL = 1k
VO = ± 0.5V
AV = 2
OUTPUT VOLTAGE STEP (V)
5
OUTPUT VOLTAGE SWING (V)
Output Voltage Step vs
Settling Time, AV = 2
Slew Rate vs Temperature
–40
HD3
HD2
–45
–50
–55
–60
0
1
4
3
5
2
OUTPUT VOLTAGE (VP-P)
6
7
INPUT IN LIMITING, AV = 3, SR = 180V/ µs
LT1187 • TPC22
Small-Signal Transient Response
LT1187 • TPC23
Small-Signal Transient Response
AV = 2, RFB = 1k, OVERSHOOT = 25%
AV = 2, RFB = 1k, OVERSHOOT = 25%
LT1187 • TPC24
LT1187 • TPC25
7
LT1187
U
W
U
U
APPLICATIO S I FOR ATIO
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 resistors: (RFB + RG)/RG.
Like the single-ended case, the differential voltage gain is
set by the external resistors: (RFB + RG)/RG. The maximum
input differential signal for which the output will respond
is approximately ±0.38V.
S/D
5
VIN
S/D
V+
3
7
+
2
– LT1187
1
+/REF
8
–/FB 4
6
V+
5
3
7
+
2
– LT1187
1
+/REF
8
–/FB 4
V IN
VOUT
V–
RFB
RG
AV = +
6
VOUT
RG
RG
AV = –
The LT1187 is quite tolerant of power supply bypassing.
In some applications a 0.1µF ceramic disc capacitor
placed 1/2 inch from the amplifier is all that is required. In
applications requiring 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 VOS at pin 8. The complete
expression for the output offset voltage is:
VOUT = (VOS + IOS(RS) + IB(RREF)) × (RFB+RG)/RG + IB(RFB)
RS represents the input source resistance, typically 75Ω,
and RREF represents the finite source impedance from the
DC reference voltage, for VREF grounded, RREF = 0Ω. The
IOS is normally a small contributor and the expression
simplifies to:
VOUT = VOS(RFB+RG)/RG + IB(RFB)
If RFB is limited to 1k the last term of the equation
contributes only 2mV, since IB is less than 2µA.
V–
RFB
RFB + RG
Power Supply Bypassing
RFB + RG
7 V+
RG
6
S/D
VIN DIFF
VIN
S/D
V+
5
3
7
+
2
– LT1187
1
+/REF
8
–/FB 4
6
V+
5
3
7
+
2
– LT1187
1
+/REF
8
–/FB 4
VIN DIFF
VOUT
V IN
RG
V–
RFB
RFB
6
Q1
VOUT
3
V–
RFB
+
RS
2
–
RS
Q2
RE
1.1k
345µA
RG
VO = (VIN DIFF + VIN)
RFB + RG
RG
VO =
(
RFB + RG
RG
(V
IN DIFF –
RFB
( R (V
G
IN
Q3
+
1 REF
RREF
Q4
8
RG
RE
1.1k
350µA
4 V–
LT1187 • AI01
Figure 1. Simplified Input Stage Schematic
8
ILT1187 • AI02
LT1187
U
W
U
U
APPLICATIO S I FOR ATIO
Operating with Low Closed-Loop Gains
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 25%.
Small-Signal Transient Response
Closed-Loop Voltage Gain vs Frequency
CLOSED-LOOP VOLTAGE GAIN (dB)
9
8
CFB = 0pF
7
AV = 2, WITH 8pF FEEDBACK CAPACITOR
6
LT1187 • AI05
5
CFB = 5pF
4
Extending the Input Range
CFB = 10pF
3
VS = ±5V
TA = 25°C
AV = 2
RFB = 900Ω
RG = 900Ω
2
1
0
–1
100k
1M
10M
FREQUENCY (Hz)
Figure 1 shows a simplified schematic of the LT1187. In
normal operation the REF pin 1 is grounded or taken to a
DC offset control voltage and differential signals are applied between pins 2 and 3. The input responds linearly
until all of the 345µA current flows through the 1.1k
resistor and Q1 (or Q2) turns off. Therefore the maximum
input swing is 380mVP or 760mVP-P. The second differential pair, Q3 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.
100M
LT1187 • AI03
Small-Signal Transient Response
Occasionally it is necessary to handle signals larger than
760mVP-P at the input. The LT1187 input stage can be
tricked to handle up to 1.5VP-P. To do this, it is necessary
to ground pin 3 and apply the differential input signal
between pin 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 technique are shown
in the following scope photo.
AV = 2, OVERSHOOT = 25%, RFB = RG = 1k
LT1187 • AI04
9
LT1187
U
W
U
U
APPLICATIO S I FOR ATIO
LT1187 in Unity Gain
Performance Characteristics section. At very high elevated temperature it is important to hold the shutdown
pin close to the negative supply to keep the supply current
from increasing.
A
Send Color Video Over Twisted-Pair
B
C
(A) STANDARD INPUTS, PINS 2 TO 3, VIN = 1.0VP-P
(B) EXTENDED INPUTS, PINS 2 TO 2, VIN = 1.0VP-P
(C) EXTENDED INPUTS, PINS 1 TO 2, VIN = 2.0VP-P
LT1187 • AI06
Using the Shutdown Feature
The LT1187 has a unique feature that allows the amplifier
to be shutdown for conserving power, or for multiplexing
several amplifiers onto a common cable. The amplifier will
shutdown by taking pin 5 to V –. In shutdown, the amplifier
dissipates 15mW while maintaining a true high impedance
output state of 20k in parallel with the feedback 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 0V
and –5V.
The ability to maintain shutoff is shown on the curve
Shutdown Supply Current vs Temperature in the Typical
1MHz Sine Wave Gated Off with Shutdown Pin
With an LT1187 it is possible to send and receive color
composite video signals more than 1000 feet on a low cost
twisted-pair. A bidirectional “video bus” consists of the
LT1195 op amp and the LT1187 video difference amplifier.
A pair of LT1195s at TRANSMIT 1, is used to generate
differential signals to drive the line which is back-terminated in its characteristic impedance. The LT1187, twistedpair receiver, converts signals from differential to singleended. 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 50Ω to boost the 3dB bandwidth of the
system from 750kHz to 4MHz. This bandwidth is adequate
to pass a 3.58MHz chroma subcarrier, and the 4.5MHz
sound subcarrier. Attenuation in the cable can be compensated by lowering the gain set resistor RG. At TRANSMIT
2, another pair of LT1195s serve the dual function to
provide cable termination via low output impedance, and
generate differential signals for TRANSMIT 2. Cable termination is made up of a 15Ω and 33Ω attenuator to reduce
the differential input signal to the LT1187. Maximum input
signal for the LT1187 is 760mVP-P.
1.5MHz Square Wave Input and Unequalized Response Through
1000 Feet of Twisted-Pair
SHUTDOWN
VOUT
AV = 2, RFB = RG = 1k
LT1187 • AI07
10
LT1187 • AI08
LT1187
U
W
U
U
APPLICATIO S I FOR ATIO
1.5MHz Square Wave Input and Equalized Response
Through 1000 Feet of Twisted-Pair
Multiburst Pattern Passed Through
1000 Feet of Twisted-Pair
LT1187 • AI10
LT1187 • AI09
Bidirectional Video Bus
TRANSMIT 1
3
+
1k
75Ω
TRANSMIT 2
+
LT1195
2
6
6
3
1k
LT1195
–
–
1k
1k
1k
1k
1k
2
1k
–
6
LT1195
3
+
6
33Ω
S/D
+
–
LT1187
+
–
R
5
75Ω
6
75Ω
2
33Ω
33Ω
15Ω
3
15Ω
2
1
15Ω
1
8
8
FB
300Ω
1000pF
RG
300Ω
RECEIVE 2
50Ω
+
–
+
–
1000pF
50Ω
+
3
S/D
3
2
1000 FEET
TWISTED-PAIR
2
LT1195
33Ω
15Ω
–
5
LT1187
6
75Ω
RFB
300Ω
RG
300Ω
RECEIVE 1
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LT1187 • AI11
11
LT1187
W
W
SI PLIFIED SCHE ATIC
7 V+
VBIAS
VBIAS
CM
+ 3
CFF
– 2
+V
6 VOUT
+V
*
4 V–
5
S/D
1 +/REF
8 –/FB
* SUBSTRATE DIODE, DO NOT FORWARD BIAS
LT1187 • SS
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
0.290 – 0.320
(7.366 – 8.128)
J8 Package
8-Lead Hermetic DIP
0.200
(5.080)
MAX
CORNER LEADS OPTION
(4 PLCS)
0.015 – 0.060
(0.381 – 1.524)
0.023 – 0.045
(0.58 – 1.14)
HALF LEAD
OPTION
0.008 – 0.018
(0.203 – 0.460)
0° – 15°
0.385 ± 0.025
(9.779 ± 0.635)
0.045 – 0.065
(1.14 – 1.65)
FULL LEAD
OPTION
0.300 – 0.320
(7.620 – 8.128)
0.045 – 0.065
(1.143 – 1.651)
8
6
7
5
0.025
(0.635)
RAD TYP
0.220 – 0.310
(5.588 – 7.874)
2
3
4
0.125
3.175
0.100 ± 0.010 MIN
(2.540 ± 0.254)
0.400
(10.160)
MAX
0.130 ± 0.005
(3.302 ± 0.127)
8
7
6
5
0.065
(1.651)
TYP
0.009 – 0.015
(0.229 – 0.381)
(
0.405
(10.287)
MAX
1
0.045 – 0.065
(1.14 – 1.65)
0.014 – 0.026
(0.360 – 0.660)
N8 Package
8-Lead Plastic DIP
0.005
(0.127)
MIN
+0.025
0.325 –0.015
+0.635
8.255
–0.381
0.250 ± 0.010
(6.350 ± 0.254)
0.125
(3.175)
MIN
0.045 ± 0.015
(1.143 ± 0.381)
)
0.100 ± 0.010
(2.540 ± 0.254)
0.020
(0.508)
MIN
1
2
4
3
0.018 ± 0.003
(0.457 ± 0.076)
0.189 – 0.197
(4.801 – 5.004)
0.010 – 0.020
× 45°
(0.254 – 0.508)
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.014 – 0.019
(0.355 – 0.483)
0.050
(1.270)
BSC
12
6
5
0.228 – 0.244
(5.791 – 6.197)
0.150 – 0.157
(3.810 – 3.988)
1
Linear Technology Corporation
7
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
S8 Package
8-Lead Plastic SOIC
8
0.053 – 0.069
(1.346 – 1.752)
2
3
4
BA/LT/GP 0293 10K REV0
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977
 LINEAR TECHNOLOGY CORPORATION 1993