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LT1187 Low Power Video Difference Amplifier FEATURES

DESCRIPTION
The LT(R)1187 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/ms, 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.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
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 Available in 8-Lead PDIP and SO Packages
APPLICATIONS

Line Receivers Video Signal Processing Cable Drivers Tape and Disc Drive Systems
TYPICAL APPLICATION
Cable Sense Amplfier for Loop Through Connections with DC Adjust
V IN 5V 3 CABLE VDC 2 1 8 VOLTAGE GAIN (dB) 40
Closed-Loop Gain vs Frequency
VS = 5V RL = 1k
+ - + -
30 6
7 LT1187 4 -5V 1k VOUT
20
10
0 1k -10 0.1
LT1187 * TA01
1 10 FREQUENCY (MHz)
100
LT1187 * TA02
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LT1187 ABSOLUTE MAXIMUM RATINGS
Total Supply Voltage (V+ to V-) .................................18V Differential Input Voltage ..........................................6V Input Voltage.............................................................VS Output Short-Circuit Duration (Note 2) .........Continuous Operating Temperature Range LT1187C .................................................. 0C to 70C LT1187I ............................................... -40C to 85C LT1187M (OBSOLETE) ...................... -55C to 150C Junction Temperature (Note 3) Plastic Packages (CN8, CS8) ............................ 150C Ceramic Packages (CJ8, MJ8) (OBSOLETE) ..... 175C Storage Temperature Range................... -65C to 150C Lead Temperature (Soldering, 10 sec) .................. 300C
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW +/REF 1 -IN 2 +IN 3 V- 4 8 7 6 5 -/FB V+ OUT S/D
ORDER PART NUMBER LT1187CN8 LT1187CS8 LT1187IN8 S8 PART MARKING 1187 LT1187MJ8 LT1187CJ8
N8 PACKAGE S8 PACKAGE 8-LEAD PDIP 8-LEAD PLASTIC SO TJMAX = 150C, JA = 100C/W (N8) TJMAX = 150C, JA = 150C/W (S8) J8 PACKAGE 8-LEAD CERDIP TJMAX = 175C, JA = 100C/W
Consider the N8 or S8 Packages for Alternate Source
OBSOLETE PACKAGE
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges.
5V ELECTRICAL CHARACTERISTICS
SYMBOL VOS IOS IB en in RIN CIN VIN LIM CMRR PSRR VOUT PARAMETERS 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 4) 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 5) S8 Package Either Input Either Input fO = 10kHz fO = 10kHz Differential Either Input (Note 6) 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 4) VO = 1V, AV = 10, RL = 1k (Notes 7, 11) VO = 1VP-P (Note 8) AV = 10 AV = 50, VO = 1.5V, 20% to 80% (Note 11) RL= 1k, VO = 125mV, 50% to 50% VO = 50mV 3V Step, 0.1% (Note 9) RL = 1k, AV = 4 (Note 10) RL = 1k, AV = 4 (Note 10) MIN LT1187C/I/M MAX 2.0 2.0 0.2 0.5 65 1.5 100 2.0 380 100 85 4.0 7.0 6.8 0.2 165 53 5.7 230 26 0 100 0.6 0.8 MAX 10 11 1.0 2.0 UNITS mV A A nV/Hz pA/Hz k pF mV V dB dB V V V % V/s MHz MHz ns ns % ns % DEGP-P
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-2.5 70 70 3.8 6.7 6.4 100
3.5
GE SR FPBW BW tr, tf tPD ts Diff AV Diff Ph
Gain Error Slew Rate Full Power Bandwidth Small-Signal Bandwidth Rise Time, Fall Time Propagation Delay Overshoot Settling Time Differential Gain Differential Phase
1.0
150
325
2
LT1187 5V ELECTRICAL CHARACTERISTICS
SYMBOL IS IS/D tON tOFF PARAMETERS Supply Current Shutdown Supply Current Shutdown Pin Current Turn-On Time Turn-On Time CONDITIONS Pin 5 at V- Pin 5 at V- Pin 5 from V- to Ground, RL = 1k Pin 5 from Ground to V-, RL = 1k
TA = 25C (Note 4) 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 LT1187C/I/M MAX 13 0.8 5 500 600 MAX 16 1.5 25 UNITS mA mA A ns ns
TA = 25C (Note 4) 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.
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 CONDITIONS Either Input (Note 5) SO Package Either Input Either Input VCM = 2.0V to 3.5V RL = 300 to Ground (Note 4) VO = 1.5V to 3.5V AV = 10 Pin 5 at V- Pin 5 at V- MIN LT1187C/I/M TYP 2.0 2.0 0.2 0.5 100 4.0 0.15 130 5.3 12 0.8 5 MAX 10 12 1.0 2.0 3.5 UNITS mV mV A A V dB V V V/s MHz mA mA A
5V ELECTRICAL CHARACTERISTICS + -
VOUT High VOUT Low
2.0 70 3.6
0.4
15 1.5 25
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
-55C TA 125C (Note 4) 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 5) 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 4) VO = 1V, AV = 10, RL = 1k Pin 5 at V- (Note 12) Pin 5 at V- -2.5 70 60 3.7 6.6 6.4 MIN LT1187M TYP 2.0 8.0 0.2 0.5 100 85 4.0 7.0 6.8 0.2 13 0.8 5 MAX 15 1.5 3.5 3.5 UNITS mV mV/C A A V dB dB V V V % mA mA A
GE IS IS/D
Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current
1.2 17 1.5 25
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LT1187 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
0C TA 70C (LT1187C) -40C TA 85C (LT1187I) (Note 4) 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 5) 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 4) VO = 1V, AV = 10, RL = 1k Pin 5 at V- (Note 12) Pin 5 at V- -2.5 70 65 3.7 6.6 6.4 MIN LT1187C/I TYP 2.0 9.0 0.2 0.5 100 85 4.0 7.0 6.8 0.2 13 0.8 5 MAX 12 1.5 3.5 3.5 UNITS mV mV/C A A V dB dB V V V % mA mA A
GE IS IS/D
Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current
1.0 17 1.5 25
0C TA 70C (LT1187C) -40C TA 85C (LT1187I) (Note 4) 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.
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 CONDITIONS Either Input (Note 5) SO Package Either Input Either Input VCM = 2.0V to 3.5V RL = 300 to Ground (Note 4) Pin 5 at V- (Note 12) Pin 5 at V- 2.0 70 3.5 MIN LT1187C/I TYP 2.0 2.0 9.0 0.2 0.5 100 4.0 0.15 12 0.8 5 MAX 12.0 13.0 1.5 3.5 3.5 UNITS mV mV V/C A A V dB V V mA mA A
5V ELECTRICAL CHARACTERISTICS + -
VOUT High VOUT Low
0.4 16 1.5 25
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 required to keep the junction temperature below absolute maximum when the output is shorted continuously. Note 3: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formulas: LT1187MJ8, LT1187CJ8: TJ = TA + (PD * 100C/W) LT1187CN8: TJ = TA + (PD * 100C/W) LT1187CS8: TJ = TA + (PD * 150C/W) Note 4: 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 5: VOS measured at the output (Pin 6) is the contribution from both input pair and is input referred.
Note 6: VIN LIM is the maximum voltage between -VIN and +VIN (Pin 2 and Pin 3) for which the output can respond. Note 7: Slew rate is measured between 0.5V on the output, with a VIN step of 0.75V, AV = 3 and RL = 1k. Note 8: Full power bandwidth is calculated from the slew rate measurement: FPBW = SR/2VP. Note 9: Settling time measurement techniques are shown in "Take the Guesswork Out of Settling Time Measurements," EDN, September 19, 1985. Note 10: NTSC (3.58MHz). 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). Note 12: See Application section for shutdown at elevated temperatures. Do not operate shutdown above TJ > 125C.
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LT1187 TYPICAL PERFORMANCE CHARACTERISTICS
Input Bias Current vs Common Mode Voltage
3.0 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 - 400 -50 INPUT BIAS CURRENT (nA) 0 VS = 5V 100 +IB
Input Bias Current vs Temperature
V+ -0.5 COMMON MODE RANGE (V) -1.0 -1.5 -2.0
Common Mode Voltage vs Temperature
V + = 1.8V TO 9V
-100 IOS -200
-IB
2.0 1.5 1.0 0.5 V- - 50 -25 V + = -1.8V TO -9V
-300
-25
50 0 25 75 TEMPERATURE (C)
100
125
0 25 75 50 TEMPERATURE (C)
100
125
LT1187 * TPC01
LT1187 * TPC02
LT1187 * TPC03
Equivalent Input Noise Voltage vs Frequency
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 VS = 5V TA = 25C RS = 0 12 10 8 6 4 2 0
Equivalent Input Noise Current vs Frequency
VS = 5V TA = 25C RS = 100k SUPPLY CURRENT (mA) 16
Supply Current vs Supply Voltage
14
- 55C 25C
12 125C 10
10
100
1k 10k FREQUENCY (Hz)
100k
8 0 2 4 6 8 SUPPLY VOLTAGE (V) 10
LT1187 * TPC04
LT1187 * TPC05
LT1187 * TPC06
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 VS/D = -VEE + 0.6V VS/D = -VEE + 0.4V -0.05 0
Gain Error vs Temperature
VS = 5V VOUT = 2V AV = 10 RL = 1k 8
Open-Loop Gain vs Temperature
VS = 5V VO = 3V RL = 1k OPEN-LOOP GAIN (kV/V) 6
-0.10
4
RL = 500
-0.15
2
-0.20 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
0 -50 -25
0 50 25 75 TEMPERATURE (C)
100
125
LT1187 * TPC07
LT1187 * TPC08
LT1187 * TPC09
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LT1187 TYPICAL PERFORMANCE CHARACTERISTICS
Gain, Phase vs Frequency
100 80 VOLTAGE GAIN (dB) 60 40 20 0 -20 100k GAIN PHASE VS = 5V TA = 25C RL = 1k 100 80 PHASE MARGIN (DEG) 60 40 20 0 -20 1M 10M FREQUENCY (Hz) 100M
LT1187 * TPC11
Open-Loop Voltage Gain vs Load Resistance
16k OPEN-LOOP VOLTAGE GAIN (V/V) GAIN BANDWIDTH PRODUCT (MHz) VS = 5V VO = 3V TA = 25C 60
Gain Bandwidth Product vs Supply Voltage
AV = 20dB TA = - 55C TA = 25C 50 TA = 125C
12k
8k
40
4k
0 100
30 1k LOAD RESISTANCE () 10k
LT1187 * TPC10
0
2
4 8 6 SUPPLY VOLTAGE (V)
10
LT1187 * TPC12
Gain Bandwidth Product and Unity Gain Phase Margin vs Temperature
60 GAIN BANDWIDTH PRODUCT (MHz) VS = 5V RL = 1k 65 100
Output Impedance vs Frequency
COMMON-MODE REJECTION RATIO (dB) VS = 5V TA = 25C 80
Common Mode Rejection Ratio vs Frequency
VS = 5V TA = 25C RL = 1k
50
GAIN BANDWIDTH PRODUCT
55
OUTPUT IMPEDANCE ()
70
PHASE MARGIN (DEG)
10
60
40
UNITY GAIN PHASE MARGIN
45
1.0
AV = 10
50
AV = 2 30 -50 35 125 0.1
40
-25
25 75 0 50 TEMPERATURE (C)
100
1k
10k
100k 1M FREQUENCY (Hz)
10M
100M
30 100k
1M 10M FREQUENCY (Hz)
100M
LT1187 * TPC15
LT1187 * TPC13
LT1187 * TPC14
Power Supply Rejection Ratio vs Frequency
80 POWER SUPPLY REJECTION RATIO (dB) OUTPUT SHORT-CIRCUIT CURRENT (mA) VS = 5V TA = 25C VRIPPLE = 300mV 36 35 34 33 32 31
Output Short-Circuit Current vs Temperature
VS = 5V OUTPUT SATURATION VOLTAGE (V)
V+ - 0.7 -0.8 -0.9
Output Swing vs Supply Voltage
125C 25C
60
40
+PSRR -PSRR
-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
20
0
-20 1k 10k 1M 100k FREQUENCY (Hz) 10M 100M
30 - 50
-25
50 0 25 75 TEMPERATURE (C)
100
125
LT1187 * TPC16
LT1187 * TPC17
LT1187 * TPC18
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LT1187 TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage Swing vs Load Resistance
5 VS = 5V OUTPUT VOLTAGE SWING (V) 3 TA = -55C TA = 25C 1 TA = 125C SLEW RATE (V/s) 250
Slew Rate vs Temperature
VS = 5V RL = 1k VO = 0.5V AV = 2 -SLEW RATE 4
Output Voltage Step vs Settling Time, AV = 2
VS = 5V TA = 25C RL = 1k
OUTPUT VOLTAGE STEP (V)
2
10mV
200 +SLEW RATE
0
-1 TA = 25C -3 TA = 125C TA = -55C
-2
10mV
-5 10 100 LOAD RESISTANCE () 1000
LT1187 * TPC19
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
Harmonic Distortion vs Output Voltage
-30 VS = 5V TA = 25C -35 RL = 1k f = 1MHz AV = 10 -40 -45 -50 -55 -60 0 1 4 3 5 2 OUTPUT VOLTAGE (VP-P) 6 7
Large-Signal Transient Response
DISTORTION (dBc)
HD3 HD2
INPUT IN LIMITING, AV = 3, SR = 180V/s
LT1187 * TPC22
LT1187 * TPC23
Small-Signal Transient Response
Small-Signal Transient Response
AV = 2, RFB = 1k, OVERSHOOT = 25%
LT1187 * TPC24
AV = 2, RFB = 1k, OVERSHOOT = 25%
LT1187 * TPC25
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LT1187 APPLICATIONS INFORMATION
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 VIN 3 2 5 V+ V IN 3 2 S/D 5 V+
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)) * (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.
1 +/REF 8 -/FB 4
7 + - LT1187
6
VOUT
1 +/REF 8 -/FB 4
7 + - LT1187
6
VOUT
V- RFB AV = + RFB + RG RG
V- RFB RFB + RG RG
7 V+
RG
RG
AV = -
6
S/D 3 2 5 V+ VIN DIFF VOUT V IN RG 3 2 7 + - LT1187
S/D 5 V+ Q1 6 VOUT 3 Q2 RE 1.1k Q3 Q4 RE 1.1k 8 RG RFB 7 + - LT1187
VIN DIFF VIN
1 +/REF 8 -/FB 4
6
1 +/REF 8 -/FB 4
+
RS
2
-
RS
+
1 REF RREF
V- RFB RFB + RG RG
V- RFB
345mA
350mA 4 V-
ILT1187 * F01
RG
VO = (VIN DIFF + VIN)
VO =
(
RFB + RG RG
(
VIN DIFF -
(R (
G
RFB
VIN
LT1187 * AI01
Figure 1. Simplified Input Stage Schematic
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LT1187 APPLICATIONS INFORMATION
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 CLOSED-LOOP VOLTAGE GAIN (dB) 8 7 6 5 4 3 CFB = 10pF CFB = 5pF CFB = 0pF AV = 2, WITH 8pF FEEDBACK CAPACITOR
LT1187 * AI05
Small-Signal Transient Response
Extending the Input Range 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 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 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 technique are shown in the following scope photo.
2 VS = 5V T = 25C 1 AA = 2 V 0 RFB = 900 RG = 900 -1 100k 1M 10M FREQUENCY (Hz)
100M
LT1187 * AI03
Small-Signal Transient Response
AV = 2, OVERSHOOT = 25%, RFB = RG = 1k
LT1187 * AI04
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LT1187 APPLICATIONS INFORMATION
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. 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 bi-directional "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 twisted-pair receiver converts signals from differential to single-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 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
(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 shut down 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
AV = 2, RFB = RG = 1k
LT1187 * AI07
LT1187 * AI08
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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 3 75 1k 2 TRANSMIT 2 3 1k 75
+
LT1195 6 6
+
LT1195
-
1k 1k
-
2
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
- + + - + -
5 LT1187
2
3
+ + 5 - LT1187 + - R
FB
3
3 2 1 8
15
75
6
6
75
300 RG 300
1000pF 50
RFB 300
RECEIVE 2
RECEIVE 1
LT1187 * AI11
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LT1187 SIMPLIFIED SCHEMATIC
VBIAS
+
VBIAS
+
7 V+
+ -
3 CFF 2 +V
CM
+V
6 VOUT
*
5 S/D 1 +/REF 8 -/FB * SUBSTRATE DIODE, DO NOT FORWARD BIAS
4 V-
LT1187 * SS
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LT1187 PACKAGE DESCRIPTION
J8 Package 8-Lead CERDIP (Narrow .300 Inch, Hermetic)
(Reference LTC DWG # 05-08-1110)
CORNER LEADS OPTION (4 PLCS) .405 (10.287) MAX 8 7 6 5
.005 (0.127) MIN
.023 - .045 (0.584 - 1.143) HALF LEAD OPTION .045 - .068 (1.143 - 1.650) FULL LEAD OPTION .300 BSC (7.62 BSC)
.025 (0.635) RAD TYP 1 2 3
.220 - .310 (5.588 - 7.874)
4
.200 (5.080) MAX .015 - .060 (0.381 - 1.524)
.008 - .018 (0.203 - 0.457)
0 - 15
NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS
.045 - .065 (1.143 - 1.651) .014 - .026 (0.360 - 0.660) .100 (2.54) BSC
.125 3.175 MIN
J8 0801
OBSOLETE PACKAGE
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13
LT1187 PACKAGE DESCRIPTION
N8 Package 8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.400* (10.160) MAX 8 7 6 5
.255 .015* (6.477 0.381)
1 .300 - .325 (7.620 - 8.255)
2
3
4 .130 .005 (3.302 0.127)
.045 - .065 (1.143 - 1.651)
.008 - .015 (0.203 - 0.381) +.035 .325 -.015 8.255 +0.889 -0.381
.065 (1.651) TYP .120 (3.048) .020 MIN (0.508) MIN .018 .003 (0.457 0.076)
N8 1002
(
)
.100 (2.54) BSC
INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
NOTE: 1. DIMENSIONS ARE
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14
LT1187 PACKAGE DESCRIPTION
S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.045 .005 .050 BSC
8
.189 - .197 (4.801 - 5.004) NOTE 3 7 6 5
.245 MIN
.160 .005 .228 - .244 (5.791 - 6.197)
.150 - .157 (3.810 - 3.988) NOTE 3
.030 .005 TYP RECOMMENDED SOLDER PAD LAYOUT
.010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254) 0- 8 TYP
1
2
3
4
.053 - .069 (1.346 - 1.752)
.004 - .010 (0.101 - 0.254)
.016 - .050 (0.406 - 1.270) NOTE: 1. DIMENSIONS IN
INCHES (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)
.014 - .019 (0.355 - 0.483) TYP
.050 (1.270) BSC
SO8 0303
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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.
15
LT1187 RELATED PARTS
PART NUMBER LT1189 LT1193 LT1194 LT1206 LT1354 LT6552 LT6559 DESCRIPTION Low Power Video Difference Amplifier Adjustable Gain Video Difference Amplifier Gain = 10 Video Difference Amplifier 250mA Out, 900V/s, 60MHz CFA 1mA, 12MHz 400V/s Op Amplifier 3.3V Video Difference Amplifier Low Cost 5V/5V Triple Video Amplifier with Shutdown
1187fa
16 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 1006 REV A * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 1993

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