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LT1187 Low Power Video Difference Amplifier
FEATURES
s s s s s s s s s s s
DESCRIPTIO
Differential or Single-Ended Gain Block (Adjustable) -3dB Bandwidth, AV = 2 50MHz Slew Rate 165V/s Low Supply Current 13mA Output Current 20mA CMRR at 10MHz 40dB LT1193 Pin Compatible Low Cost Single 5V Operation Drives Cables Directly Output Shutdown
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. The LT1187's high slew rate, 165V/s, 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.
APPLICATI
s s s s
S
Line Receivers Video Signal Processing Cable Drivers Tape and Disc Drive Systems
TYPICAL APPLICATI
Cable Sense Amplifier for Loop Through Connections with DC Adjust
40
V IN 5V CABLE VDC 2 1 8 + - LT1187 + - 4 -5V 1k 7 6 VOUT
Closed-Loop Gain vs Frequency
30
VOLTAGE GAIN (dB)
3
20
10
0
1k
LT1187 * TA01
-10 0.1
U
VS = 5V RL = 1k 1 10 FREQUENCY (MHz) 100
LT1187 * TA02
UO
UO
1
LT1187 ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW +/REF -IN +IN V- 1 2 3 4 8 7 6 5 -/FB V+ OUT S/D
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 ..................................... - 55C to 150C LT1187C............................................. 0C to 70C Junction Temperature (Note 2) Plastic Package (CN8,CS8) ......................... 150C Ceramic Package (CJ8,MJ8) ....................... 175C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec.)................ 300C
ORDER PART NUMBER LT1187MJ8 LT1187CJ8 LT1187CN8 LT1187CS8 S8 PART MARKING 1187
J8 PACKAGE N8 PACKAGE 8-LEAD HERMETIC DIP 8-LEAD PLASTIC DIP S8 PACKAGE 8-LEAD PLASTIC SOIC
LT1187 * POI01
TJMAX = 175C, JA = 100C/W (J8) TJMAX = 150C, JA = 100C/W (N8) TJMAX = 150C, JA = 150C/W (S8)
Consult factory for Industrial grade parts.
+5V ELECTRICAL CHARACTERISTICS -
SYMBOL VOS IOS IB en in RIN CIN VIN LIM CMRR PSRR VOUT PARAMETER Input Offset Voltage Input Offset Current Input Bias Current Input Noise Voltage Input Noise Current Input Resistance Input Capacitance Input Voltage Limit Input Voltage Range Common-Mode Rejection Ratio Power Supply Rejection Ratio Output Voltage Swing
TA = 25C, (Note 3) VS = 5V, VREF = 0V, RFB1 = 900 from pins 6 to 8, RFB2 = 100 from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL 10pF, pin 5 open.
CONDITIONS Either Input, (Note 4) SOIC Package Either Input Either Input fO = 10kHz fO = 10kHz Differential Either Input (Note 5) -2.5 VCM = -2.5V to 3.5V VS = 2.375V to 8V VS = 5V, RL = 1k, AV = 50 VS = 8V, RL = 1k, AV = 50 VS = 8V, RL = 300, AV = 50, (Note 3) GE SR FPBW BW tr, tf tPD ts Diff AV Diff Ph IS Gain Error Slew Rate Full Power Bandwidth Small Signal Bandwidth Rise Time, Fall Time Propagation Delay Overshoot Settling Time Differential Gain Differential Phase Supply Current Shutdown Supply Current Pin 5 at V - VO = 1V, AV = 10, RL = 1k (Note 6, 10) VO = 1VP-P, (Note 7) AV = 10 AV = 50, VO = 1.5V, 20% to 80% (Note 10) RL= 1k, VO = 125mV, 50% to 50% VO = 50mV 3V Step, 0.1%, (Note 8) RL = 1k, AV = 4, (Note 9) RL = 1k, AV = 4, (Note 9) 150 100 70 70 3.8 6.7 6.4 100 85 4.0 7.0 6.8 0.2 165 53 5.7 230 26 0 100 0.6 0.8 13 0.8 16 1.5 325 1.0 % V/s MHz MHz ns ns % ns % DEGP-P mA mA MIN LT1187M/C TYP MAX 2.0 10 2.0 11 0.2 0.5 65 1.5 100 2.0 380 3.5 1.0 2.0 UNITS mV mV A A nV/Hz pA/Hz k pF mV V dB dB V
2
U
W
U
U
WW
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LT1187 +5V ELECTRICAL CHARACTERISTICS -
SYMBOL IS/D tON tOFF PARAMETER Shutdown Pin Current Turn On Time Turn Off Time CONDITIONS Pin 5 at V - Pin 5 from V - to Ground, RL = 1k Pin 5 from Ground to V -, RL = 1k
TA = 25C, (Note 3) VS = 5V, VREF = 0V, RFB1 = 900 from pins 6 to 8, RFB2 = 100 from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL 10pF, pin 5 open.
MIN LT1187M/C TYP MAX 5 500 600 25 UNITS A ns ns
5V ELECTRICAL CHARACTERISTICS + -
SYMBOL VOS IOS IB CMRR VOUT SR BW IS IS/D PARAMETER Input Offset Voltage Input Offset Current Input Bias Current Input Voltage Range Common-Mode Rejection Ratio Output Voltage Swing Slew Rate Small-Signal Bandwidth Supply Current Shutdown Supply Current Shutdown Pin Current Pin 5 at V
-
TA = 25C, (Note 3) VS = 5V, VS = 0V, VREF = 2.5V, RFB1 = 900 from pins 6 to 8, RFB2 = 100 from pin 8 to VREF, RL = RFB1 + RFB2 = 1k, CL 10pF, pin 5 open.
CONDITIONS Either Input, (Note 4) SOIC Package Either Input Either Input 2.0 VCM = 2.0V to 3.5V RL = 300 to Ground (Note 3) VO = 1.5V to 3.5V AV = 10 VOUT High VOUT Low 70 3.6 100 4.0 0.15 130 5.3 12 0.8 5 Pin 5 at V - 15 1.5 25 0.4 V/s MHz mA mA A MIN LT1187M/C TYP MAX 2.0 2.0 0.2 0.5 10 12 1.0 2.0 3.5 UNITS mV mV A A V dB V
+5V ELECTRICAL CHARACTERISTICS -
SYMBOL VOS VOS /T IOS IB CMRR PSRR VOUT PARAMETER Input Offset Voltage Input VOS Drift Input Offset Current Input Bias Current Input Voltage Range Common-Mode Rejection Ratio Power Supply Rejection Ratio Output Voltage Swing Either Input Either Input CONDITIONS
-55C TA 125C, (Note 3) VS = 5V, VREF = 0V, RFB1 = 900 from pins 6 to 8, RFB2 = 100 from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL 10pF, pin 5 open.
MIN LT1187M TYP MAX 2.0 8.0 0.2 0.5 -2.5 VCM = -2.5V to 3.5V VS = 2.375V to 8V VS = 5V, RL = 1k, AV = 50 VS = 8V, RL = 1k, AV = 50 VS = 8V, RL = 300, AV = 50, (Note 3) GE IS IS/D Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current Pin 5 at V -, (Note 11) Pin 5 at V
-
UNITS mV V/C A A V dB dB V
Either Input, (Note 4)
15 1.5 3.5 3.5
70 60 3.7 6.6 6.4
100 85 4.0 7.0 6.8 0.2 13 0.8 5 1.2 17 1.5 25
VO = 1V, AV = 10, RL = 1k
% mA mA A
3
LT1187 +5V ELECTRICAL CHARACTERISTICS 0C TA 70C, (Note 3) - = 5V, V = 0V, R = 900 from pins 6 to 8, R = 100 from pin 8 to ground, R = R V
S REF FB1 FB2 L FB1
+ RFB2 = 1k, CL 10pF, pin 5 open.
MIN LT1187C TYP MAX 2.0 9.0 0.2 0.5 - 2.5 70 65 3.7 6.6 6.4 100 85 4.0 7.0 6.8 0.2 13 0.8 5 1.0 17 1.5 25 % mA mA A 12 1.5 3.5 3.5 UNITS mV V/C A A V dB dB V
SYMBOL VOS VOS /T IOS IB CMRR PSRR VOUT
PARAMETER Input Offset Voltage Input VOS Drift Input Offset Current Input Bias Current Input Voltage Range Common-Mode Rejection Ratio Power Supply Rejection Ratio Output Voltage Swing
CONDITIONS Either Input, (Note 4) Either Input Either Input VCM = -2.5V to 3.5V VS = 2.375V to 8V VS = 5V, RL = 1k, AV = 50 VS = 8V, RL = 1k, AV = 50 VS = 8V, RL = 300, AV = 50, (Note 3)
GE IS IS/D
Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current
VO = 1V, AV = 10, RL = 1k Pin 5 at V , (Note 11) Pin 5 at V -
-
5V ELECTRICAL CHARACTERISTICS + -
SYMBOL VOS VOS/T IOS IB CMRR VOUT IS IS/D PARAMETER Input Offset Voltage Input VOS Drift Input Offset Current Input Bias Current Input Voltage Range Common-Mode Rejection Ratio Output Voltage Swing Supply Current Shutdown Supply Current Shutdown Pin Current Either Input Either Input CONDITIONS
0C TA 70C, (Note 3) VS = 5V, VS = 0V, VREF = 2.5V, RFB1 = 900 from pins 6 to 8, RFB2 = 100 from pin 8 to VREF, RL = RFB1 + RFB2 = 1k, CL 10pF, pin 5 open.
MIN LT1187C TYP MAX 2.0 2.0 9.0 0.2 0.5 2.0 VCM = 2.0V to 3.5V RL = 300 to Ground (Note 3) Pin 5 at V -, (Note 11) Pin 5 at V - VOUT High VOUT Low 70 3.5 100 4.0 0.15 12 0.8 5 0.4 16 1.5 25 mA mA A 1.5 3.5 3.5 12.0 13.0 UNITS mV mV V/C A A V dB V
Either Input, (Note 4) SOIC Package
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 x 100C/W) LT1187CN8: TJ = TA + (PD x 100C/W) LT1187CS8: TJ = TA + (PD x 150C/W) Note 3: When RL = 1k is specified, the load resistor is RFB1 + RFB2, but when RL = 300 is specified, then an additional 430 is added to the output such that (RFB1 + RFB2) in parallel with 430 is RL = 300. 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.
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/2Vp. 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 > 125C.
4
LT1187
TYPICAL PERFOR A CE CHARACTERISTICS
Input Bias Current vs Common-Mode Voltage
3.0 VS = 5V 2.5
INPUT BIAS CURRENT (A)
2.0 1.5 1.0 0.5 0 -0.5 -5 -4 -3 -2 -1 0 1 2 3 COMMON-MODE VOLTAGE (V) 4 5 -55C 25C 125C
COMMON-MODE RANGE (V)
INPUT BIAS CURRENT (nA)
Equivalent Input Noise Voltage vs Frequency
VS = 5V TA = 25C RS = 0
EQUIVALENT INPUT NOISE CURRENT (pA/Hz)
EQUIVALENT INPUT NOISE VOLTAGE (nV/Hz)
600 500 400 300 200 100 0 10 100 1k 10k FREQUENCY (Hz) 100k
8 6 4 2 0 10 100 1k 10k FREQUENCY (Hz) 100k
SUPPLY CURRENT (mA)
Shutdown Supply Current vs Temperature
6
SHUTDOWN SUPPLY CURRENT (mA)
VS = 5V 5 GAIN ERROR (%) 4 3 VS/D = -VEE + 0.2V 2 1 VS/D = -VEE 0 -50 -25 50 0 25 75 TEMPERATURE (C) 100 125
-0.20 -50 -25 -0.05
VS/D = -VEE + 0.6V VS/D = -VEE + 0.4V
OPEN-LOOP GAIN (kV/V)
UW
LT1187 * TPC01
Input Bias Current vs Temperature
100 +IB
Common-Mode Voltage vs Temperature
V+ -0.5 V + = 1.8V TO 9V
0
-1.0 -1.5 -2.0
-100 IOS -200
-IB
2.0 1.5 1.0 0.5 V- - 50 -25 V + = -1.8V TO -9V
-300
- 400 -50
-25
0 25 75 50 TEMPERATURE (C)
100
125
0 25 75 50 TEMPERATURE (C)
100
125
LT1187 * TPC02
LT1187 * TPC03
Equivalent Input Noise Current vs Frequency
12 10 VS = 5V TA = 25C RS = 100k
16
Supply Current vs Supply Voltage
14
- 55C 25C
12 125C 10
8 0 2 4 6 8 SUPPLY VOLTAGE (V) 10
LT1187 * TPC04
LT1187 * TPC05
LT1187 * TPC06
Gain Error vs Temperature
0 VS = 5V VOUT = 2V AV = 10 RL = 1k 8
Open-Loop Gain vs Temperature
VS = 5V VO = 3V 6
RL = 1k
-0.10
4
RL = 500
-0.15
2
0 25 50 75 TEMPERATURE (C)
100
125
0 -50 -25
25 75 0 50 TEMPERATURE (C)
100
125
LT1187 * TPC07
LT1187 * TPC08
LT1187 * TPC09
5
LT1187
TYPICAL PERFOR A CE CHARACTERISTICS
Gain, Phase vs Frequency
100 80
VOLTAGE GAIN (dB)
OPEN-LOOP VOLTAGE GAIN (V/V)
80
PHASE MARGIN (DEG)
GAIN BANDWIDTH PRODUCT (MHz)
PHASE
60 40 20 0 -20 100k GAIN
1M 10M FREQUENCY (Hz)
Gain Bandwidth Product and Unity Gain Phase Margin vs Temperature
60 65 VS = 5V RL = 1k GAIN BANDWIDTH PRODUCT 100
COMMON-MODE REJECTION RATIO (dB)
GAIN BANDWIDTH PRODUCT (MHz)
50
55
OUTPUT IMPEDANCE ()
40
UNITY GAIN PHASE MARGIN
30 -50
-25
25 75 0 50 TEMPERATURE (C)
Power Supply Rejection Ratio vs Frequency
80 36
OUTPUT SHORT CIRCUIT CURRENT (mA)
POWER SUPPLY REJECTION RATIO (dB)
OUTPUT SATURATION VOLTAGE (V)
60 +PSRR -PSRR
VS = 5V TA = 25C VRIPPLE = 300mV
40
20
0
-20 1k 10k 1M 100k FREQUENCY (Hz) 10M 100M
6
UW
VS = 5V TA = 25C RL = 1k 100M
LT1187 * TPC11
Open-Loop Voltage Gain vs Load Resistance
100
16k VS = 5V VO = 3V TA = +25C 60
Gain Bandwidth Product vs Supply Voltage
AV = 20dB TA = - 55C TA = 25C 50 TA = 125C
12k
60 40 20 0
8k
40
4k
-20
0 100
30 1k LOAD RESISTANCE () 10k 0 2 4 8 6 SUPPLY VOLTAGE (V) 10
LT1187 * TPC12
Output Impedance vs Frequency
80
VS = 5V TA = 25C
Common-Mode Rejection Ratio vs Frequency
VS = 5V TA = 25C RL = 1k
70
PHASE MARGIN (DEG)
10
60
45
1.0
AV = 10
50
AV = 2 35 125 0.1
40
100
1k
10k
100k 1M FREQUENCY (Hz)
10M
100M
30 100k
1M 10M FREQUENCY (Hz)
100M
LT1187 * TPC15
LT1187 * TPC13
LT1187 * TPC14
Output Short Circuit Current vs Temperature
VS = 5V 35 34 33 32 31 30 - 50
V+ - 0.7 -0.8 -0.9
Output Swing vs Supply Voltage
125C 25C
-1.0 -1.1 0.5 0.4 0.3 0.2 0.1 V- 0 2 -55C 4 6 8 SUPPLY VOLTAGE (V) 10 -55C RL = 1k 1.8V VS 9V 125C 25C
-25
50 0 25 75 TEMPERATURE (C)
100
125
LT1187 * TPC16
LT1187 * TPC17
LT1187 * TPC18
LT1187
TYPICAL PERFOR A CE CHARACTERISTICS
Output Voltage Swing vs Load Resistance
5 VS = 5V OUTPUT VOLTAGE SWING (V) 3 TA = -55C TA = 25C 1 TA = 125C 250 VS = 5V RL = 1k VO = 0.5V AV = 2
OUTPUT VOLTAGE STEP (V)
SLEW RATE (V/s)
-1 TA = 25C -3 TA = 125C TA = -55C
-5 10 100 LOAD RESISTANCE () 1000
LT1187 * TPC19
Harmonic Distortion vs Output Voltage
-30 -35 DISTORTION (dBc) -40 -45 -50 -55 -60 0 1 4 3 5 2 OUTPUT VOLTAGE (VP-P) 6 7 VS = 5V TA = 25C RL = 1k f = 1MHz AV = 10
Small-Signal Transient Response
AV = 2, RFB = 1k, OVERSHOOT = 25%
LT1187 * TPC24
UW
Slew Rate vs Temperature
4
Output Voltage Step vs Settling Time, AV = 2
VS = 5V TA = 25C RL = 1k 2
10mV
-SLEW RATE
200 +SLEW RATE
0
-2
10mV
150 -50 -25
-4 0 25 50 75 TEMPERATURE (C) 100 125 40 50 60 70 80 SETTLING TIME (ns) 90 100
LT1187 * TPC20
LT1187 * TPC21
Large-Signal Transient Response
HD3 HD2
INPUT IN LIMITING, AV = 3, SR = 180V/ s
LT1187 * TPC22
LT1187 * TPC23
Small-Signal Transient Response
AV = 2, RFB = 1k, OVERSHOOT = 25%
LT1187 * TPC25
7
LT1187 APPLICATIO S I FOR ATIO U
Power Supply Bypassing The LT1187 is quite tolerant of power supply bypassing. In some applications a 0.1F 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 0.1F ceramic disc in parallel with a 4.7F 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)) x (RFB+RG)/RG + IB(RFB) RS represents the input source resistance, typically 75, and RREF represents the finite source impedance from the DC reference voltage, for VREF grounded, RREF = 0. 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 2A.
RFB + RG RG 6 VOUT
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+ V IN
3 7 + 2 - LT1187 1 +/REF 8 -/FB 4 V- RFB AV = +
6
VOUT
RG
RFB + RG RG
S/D V+ 5 3 7 + 2 - LT1187 1 +/REF 8 -/FB 4 V- RFB RFB + RG RG
VIN DIFF VIN
6
VIN DIFF VOUT V IN RG
RG
VO = (VIN DIFF + VIN)
VO =
8
W
RG
U
U
V+ 5 3 7 + 2 - LT1187 1 +/REF 8 -/FB 4 V- RFB
AV = -
7 V+
6
S/D V+ 5 3 7 + 2 - LT1187 1 +/REF 8 -/FB 4 V- RFB
RFB
6 VOUT
Q1 3
Q2 RE 1.1k
Q3
Q4 RE 1.1k
8 RG
+
RS
2
-
RS
+
1 REF RREF
345A
350A 4 V-
ILT1187 * AI02
(
RFB + RG RG
(V
IN DIFF -
( R (V
G
RFB
IN
LT1187 * AI01
Figure 1. Simplified Input Stage Schematic
LT1187 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%.
Closed-Loop Voltage Gain vs Frequency
9 8 7 6 5 4 3 2 1 0 -1 100k VS = 5V TA = 25C AV = 2 RFB = 900 RG = 900 1M 10M FREQUENCY (Hz) 100M
LT1187 * AI03
CLOSED-LOOP VOLTAGE GAIN (dB)
CFB = 0pF
CFB = 5pF CFB = 10pF
Small-Signal Transient Response
AV = 2, OVERSHOOT = 25%, RFB = RG = 1k
LT1187 * AI04
U
Small-Signal Transient Response
AV = 2, WITH 8pF FEEDBACK CAPACITOR
LT1187 * AI05
W
U
U
Extending the Input Range 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 345A 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. 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.
9
LT1187 APPLICATIO S I FOR ATIO
LT1187 in Unity Gain
A
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
SHUTDOWN
VOUT
AV = 2, RFB = RG = 1k
LT1187 * AI07 LT1187 * AI08
10
U
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. Send Color Video Over Twisted-Pair 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 50 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 15 and 33 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
W
U
U
LT1187 APPLICATIO S I FOR ATIO U
Multiburst Pattern Passed Through 1000 Feet of Twisted-Pair
LT1187 * AI10
1.5MHz Square Wave Input and Equalized Response Through 1000 Feet of Twisted-Pair
TRANSMIT 1 3 75 1k 2
+
LT1195 6 6
-
1k 1k
1k 1k 1k
2
-
LT1195 6 33 S/D 33 33 15 15 15 1000 FEET TWISTED-PAIR 33 S/D 3 2 1 8 1000pF 50 RG 300 6 LT1195
3
+ + - LT1187 + - R
5
FB
75
6
300 RG 300
RECEIVE 2
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.
W
3 2 1 8
U
U
LT1187 * AI09
Bidirectional Video Bus
TRANSMIT 2 3 1k 75
+
LT1195
-
2
1k
- + + - + -
5 LT1187
2
3
15
6
75
1000pF 50
RFB 300
RECEIVE 1
LT1187 * AI11
11
LT1187 SI PLIFIED SCHE ATIC
7 V+ VBIAS VBIAS
+3 CFF -2 +V
5 S/D 1 +/REF 8 -/FB * SUBSTRATE DIODE, DO NOT FORWARD BIAS
PACKAGE DESCRIPTIO
0.290 - 0.320 (7.366 - 8.128)
J8 Package 8-Lead Hermetic DIP
0.008 - 0.018 (0.203 - 0.460) 0.385 0.025 (9.779 0.635)
0.300 - 0.320 (7.620 - 8.128)
N8 Package 8-Lead Plastic DIP
0.009 - 0.015 (0.229 - 0.381)
(
+0.025 0.325 -0.015 +0.635 8.255 -0.381
)
0.010 - 0.020 x 45 (0.254 - 0.508)
S8 Package 8-Lead Plastic SOIC
0- 8 TYP
0.016 - 0.050 0.406 - 1.270
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
U
W
W
CM
+V
6 VOUT
*
4 V-
LT1187 * SS
Dimensions in inches (millimeters) unless otherwise noted.
0.405 (10.287) MAX 8 7 6 5
CORNER LEADS OPTION (4 PLCS)
0.200 (5.080) MAX 0.015 - 0.060 (0.381 - 1.524)
0.005 (0.127) MIN
0.023 - 0.045 (0.58 - 1.14) HALF LEAD OPTION 0 - 15 0.045 - 0.065 (1.14 - 1.65) FULL LEAD OPTION
0.025 (0.635) RAD TYP 1 2 3
0.220 - 0.310 (5.588 - 7.874)
4
0.045 - 0.065 (1.14 - 1.65) 0.014 - 0.026 (0.360 - 0.660)
0.125 3.175 0.100 0.010 MIN (2.540 0.254)
0.045 - 0.065 (1.143 - 1.651)
0.130 0.005 (3.302 0.127)
0.400 (10.160) MAX 8 7 6 5
0.065 (1.651) TYP 0.125 (3.175) MIN 0.020 (0.508) MIN
0.250 0.010 (6.350 0.254)
0.045 0.015 (1.143 0.381) 0.100 0.010 (2.540 0.254)
1
2
3
4
0.018 0.003 (0.457 0.076) 0.189 - 0.197 (4.801 - 5.004)
0.053 - 0.069 (1.346 - 1.752) 0.004 - 0.010 (0.101 - 0.254) 0.228 - 0.244 (5.791 - 6.197)
8
7
6
5
0.008 - 0.010 (0.203 - 0.254)
0.014 - 0.019 (0.355 - 0.483)
0.050 (1.270) BSC
0.150 - 0.157 (3.810 - 3.988)
1
2
3
4
BA/LT/GP 0293 10K REV0
(c) LINEAR TECHNOLOGY CORPORATION 1993

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