LINER LT1187MJ8 Low power video difference amplifi er Datasheet

LT1187
Low Power
Video Difference Amplifier
FEATURES
DESCRIPTION
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The LT®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.
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■
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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
Available in 8-Lead PDIP and SO Packages
APPLICATIONS
■
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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.
Line Receivers
Video Signal Processing
Cable Drivers
Tape and Disc Drive Systems
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Cable Sense Amplfier for Loop Through Connections with DC Adjust
Closed-Loop Gain vs Frequency
40
V IN
5V
CABLE
2
VDC
1
8
+
–
+
–
30
7
LT1187
6
VOUT
4
–5V
VOLTAGE GAIN (dB)
3
VS = ±5V
RL = 1k
20
10
1k
0
1k
–10
0.1
LT1187 • TA01
1
10
FREQUENCY (MHz)
100
LT1187 • TA02
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LT1187
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
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 .................................................. 0°C to 70°C
LT1187I ............................................... –40°C to 85°C
LT1187M (OBSOLETE) ...................... –55°C to 150°C
Junction Temperature (Note 3)
Plastic Packages (CN8, CS8) ............................ 150°C
Ceramic Packages (CJ8, MJ8) (OBSOLETE) ..... 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
LT1187CN8
LT1187CS8
LT1187IN8
N8 PACKAGE
S8 PACKAGE
8-LEAD PDIP
8-LEAD PLASTIC SO
TJMAX = 150°C, θJA = 100°C/W (N8)
TJMAX = 150°C, θJA = 150°C/W (S8)
S8 PART MARKING
1187
J8 PACKAGE 8-LEAD CERDIP
TJMAX = 175°C, θJA = 100°C/W
LT1187MJ8
LT1187CJ8
OBSOLETE PACKAGE
Consider the N8 or S8 Packages for Alternate Source
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
TA = 25°C (Note 4)
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
VOS
PARAMETERS
Input Offset Voltage
IOS
IB
en
in
RIN
CIN
VIN LIM
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
CMRR
PSRR
VOUT
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
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 = 300Ω, 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
–2.5
70
70
±3.8
±6.7
±6.4
100
150
LT1187C/I/M
MAX
2.0
2.0
0.2
±0.5
65
1.5
100
2.0
±380
MAX
10
11
1.0
±2.0
3.5
100
85
±4.0
±7.0
±6.8
0.2
165
53
5.7
230
26
0
100
0.6
0.8
1.0
325
UNITS
mV
µA
µA
nV/√Hz
pA/√Hz
kΩ
pF
mV
V
dB
dB
V
V
V
%
V/µs
MHz
MHz
ns
ns
%
ns
%
DEGP-P
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LT1187
±5V ELECTRICAL CHARACTERISTICS
TA = 25°C (Note 4)
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
IS
IS/D
tON
tOFF
PARAMETERS
Supply Current
Shutdown Supply Current
Shutdown Pin Current
Turn-On Time
Turn-On Time
CONDITIONS
MIN
Pin 5 at V–
Pin 5 at V–
Pin 5 from V– to Ground, RL = 1k
Pin 5 from Ground to V–, RL = 1k
LT1187C/I/M
MAX
13
0.8
5
500
600
MAX
16
1.5
25
UNITS
mA
mA
µA
ns
ns
5V
ELECTRICAL
CHARACTERISTICS
+
–
TA = 25°C (Note 4)
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
VOS
PARAMETER
Input Offset Voltage
IOS
IB
Input Offset Current
Input Bias Current
Input Voltage Range
Common Mode Rejection Ratio
Output Voltage Swing
CMRR
VOUT
SR
BW
IS
IS/D
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 = 300Ω to Ground
(Note 4)
MIN
VOUT High
VOUT Low
2.0
70
3.6
VO = 1.5V to 3.5V
AV = 10
Pin 5 at V–
Pin 5 at V–
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
0.4
15
1.5
25
UNITS
mV
mV
µA
µA
V
dB
V
V
V/µs
MHz
mA
mA
µA
±5V ELECTRICAL CHARACTERISTICS
–55°C ≤ TA ≤ 125°C (Note 4)
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
VOS
ΔVOS/ΔT
IOS
IB
CMRR
PSRR
VOUT
GE
IS
IS/D
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
Gain Error
Supply Current
Shutdown Supply Current
Shutdown Pin Current
CONDITIONS
Either Input (Note 5)
MIN
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 = 300Ω, 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
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
1.2
17
1.5
25
UNITS
mV
mV/°C
µA
µA
V
dB
dB
V
V
V
%
mA
mA
µA
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LT1187
±5V ELECTRICAL CHARACTERISTICS
0°C ≤ TA ≤ 70°C (LT1187C) –40°C ≤ TA ≤ 85°C (LT1187I) (Note 4)
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
VOS
ΔVOS/ΔT
IOS
IB
CMRR
PSRR
VOUT
GE
IS
IS/D
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
Gain Error
Supply Current
Shutdown Supply Current
Shutdown Pin Current
CONDITIONS
Either Input (Note 5)
MIN
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 = 300Ω, AV = 50 (Note 4)
VO = ±1V, AV = 10, RL = 1k
–2.5
70
65
±3.7
±6.6
±6.4
Pin 5 at V– (Note 12)
Pin 5 at V–
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
1.0
17
1.5
25
UNITS
mV
mV/°C
µA
µA
V
dB
dB
V
V
V
%
mA
mA
µA
5V
ELECTRICAL
CHARACTERISTICS
+
–
0°C ≤ TA ≤ 70°C (LT1187C) –40°C ≤ TA ≤ 85°C (LT1187I) (Note 4)
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
VOS
PARAMETER
Input Offset Voltage
ΔVOS/ΔT
IOS
IB
Input VOS Drift
Input Offset Current
Input Bias Current
Input Voltage Range
Common Mode Rejection Ratio
Output Voltage Swing
CMRR
VOUT
IS
IS/D
Supply Current
Shutdown Supply Current
Shutdown Pin Current
CONDITIONS
Either Input (Note 5)
SO Package
MIN
Either Input
Either Input
VCM = 2.0V to 3.5V
RL = 300Ω to Ground
(Note 4)
Pin 5 at V– (Note 12)
Pin 5 at V–
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 • 100°C/W)
LT1187CN8:
TJ = TA + (PD • 100°C/W)
LT1187CS8:
TJ = TA + (PD • 150°C/W)
Note 4: 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 5: VOS measured at the output (Pin 6) is the contribution from both
input pair and is input referred.
VOUT High
VOUT Low
2.0
70
3.5
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
0.4
16
1.5
25
UNITS
mV
mV
µV/°C
µA
µA
V
dB
V
V
mA
mA
µA
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/2πVP.
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 > 125°C.
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LT1187
TYPICAL PERFORMANCE CHARACTERISTICS
Input Bias Current vs
Common Mode Voltage
V+
100
VS = ±5V
1.5
1.0
–55°C
0.5
25°C
0
+IB
0
–100
COMMON MODE RANGE (V)
INPUT BIAS CURRENT (nA)
INPUT BIAS CURRENT (µA)
2.0
–IB
IOS
–200
–300
125°C
– 5 – 4 –3 –2 –1 0 1 2 3
COMMON MODE VOLTAGE (V)
– 400
–50
5
4
–25
50
0
25
75
TEMPERATURE (°C)
300
200
100
0
1k
10k
FREQUENCY (Hz)
12
10
8
6
4
V + = –1.8V TO –9V
Supply Current vs Supply Voltage
16
100
25°C
12
125°C
10
1k
10k
FREQUENCY (Hz)
8
100k
5
2
GAIN ERROR (%)
–0.05
VS/D = –VEE + 0.2V
4
6
8
±SUPPLY VOLTAGE (V)
10
LT1187 • TPC06
Open-Loop Gain vs Temperature
VS = ±5V
VOUT = ±2V
AV = 10
RL = 1k
VS = ±5V
VS/D = –VEE + 0.4V
2
0
Gain Error vs Temperature
0
3
– 55°C
14
LT1187 • TPC05
6
125
100
LT1187 • TPC03
0
10
100k
VS/D = –VEE + 0.6V
0
25
75
50
TEMPERATURE (°C)
2
Shutdown Supply Current vs
Temperature
SHUTDOWN SUPPLY CURRENT (mA)
1.5
1.0
V–
– 50 –25
125
VS = ±5V
TA = 25°C
RS = 100k
LT1187 • TPC04
4
100
SUPPLY CURRENT (mA)
400
EQUIVALENT INPUT NOISE CURRENT (pA/√Hz)
EQUIVALENT INPUT NOISE VOLTAGE (nV/√Hz)
VS = ±5V
TA = 25°C
RS = 0Ω
100
2.0
Equivalent Input Noise Current vs
Frequency
Equivalent Input Noise Voltage vs
Frequency
500
–1.5
–2.0
LT1187 • TPC02
LT1187 • TPC01
600
–1.0
0.5
–0.5
10
V + = 1.8V TO 9V
–0.5
2.5
–0.10
–0.15
8
VS = ±5V
VO = ±3V
RL = 1k
OPEN-LOOP GAIN (kV/V)
3.0
Common Mode Voltage vs
Temperature
Input Bias Current vs Temperature
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
0
50
25
75
TEMPERATURE (°C)
100
125
LT1187 • TPC09
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LT1187
TYPICAL PERFORMANCE CHARACTERISTICS
Open-Loop Voltage Gain vs
Load Resistance
Gain, Phase vs Frequency
60
40
GAIN
20
20
0
PHASE MARGIN (DEG)
VOLTAGE GAIN (dB)
80
60
40
16k
0
–20
100k
12k
8k
4k
–20
1M
10M
FREQUENCY (Hz)
60
VS = ±5V
VO = ±3V
TA = 25°C
GAIN BANDWIDTH PRODUCT (MHz)
PHASE
80
100
VS = ±5V
TA = 25°C
RL = 1k
OPEN-LOOP VOLTAGE GAIN (V/V)
100
1k
LOAD RESISTANCE (Ω)
–25
25
75
0
50
TEMPERATURE (°C)
100
10
AV = 10
1.0
35
125
0.1
10k
1k
100k
1M
FREQUENCY (Hz)
LT1187 • TPC13
36
+PSRR
–PSRR
20
0
–20
1k
10k
1M
100k
FREQUENCY (Hz)
10M
2
4
8
6
±SUPPLY VOLTAGE (V)
100M
LT1187 • TPC16
10M
Common Mode Rejection Ratio
vs Frequency
VS = ±5V
TA = 25°C
RL = 1k
70
60
50
40
30
100k
100M
1M
10M
FREQUENCY (Hz)
34
33
32
31
30
– 50
–25
50
0
25
75
TEMPERATURE (°C)
100
125
LT1187 • TPC17
100M
LT1187 • TPC15
V+
– 0.7
VS = ±5V
35
10
LT1187 • TPC12
OUTPUT SATURATION VOLTAGE (V)
VS = ± 5V
TA = 25°C
VRIPPLE = ±300mV
40
0
Output Short-Circuit Current vs
Temperature
OUTPUT SHORT-CIRCUIT CURRENT (mA)
POWER SUPPLY REJECTION RATIO (dB)
60
40
LT1187 • TPC14
Power Supply Rejection Ratio vs
Frequency
80
TA = 125°C
80
VS = ±5V
TA = 25°C
AV = 2
30
–50
50
10k
COMMON-MODE REJECTION RATIO (dB)
OUTPUT IMPEDANCE (Ω)
45
100
PHASE MARGIN (DEG)
GAIN BANDWIDTH PRODUCT (MHz)
65
55
UNITY GAIN
PHASE MARGIN
40
TA = 25°C
Output Impedance vs Frequency
GAIN BANDWIDTH
PRODUCT
50
TA = – 55°C
LT1187 • TPC10
Gain Bandwidth Product and
Unity Gain Phase Margin vs
Temperature
VS = ±5V
RL = 1k
AV = 20dB
30
0
100
100M
LT1187 • TPC11
60
Gain Bandwidth Product vs
Supply Voltage
±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
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LT1187
TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage Swing vs
Load Resistance
250
TA = –55°C
SLEW RATE (V/µs)
TA = 25°C
TA = 125°C
1
–1
TA = 25°C
–3
TA = 125°C
10
4
VS = ±5V
RL = 1k
VO = ±0.5V
AV = 2
–SLEW RATE
200
+SLEW RATE
TA = –55°C
–5
100
LOAD RESISTANCE (Ω)
150
–50 –25
1000
LT1187 • TPC19
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)
90
100
LT1187 • TPC21
LT1187 • TPC20
Harmonic Distortion vs
Output Voltage
Large-Signal Transient Response
–30
DISTORTION (dBc)
OUTPUT VOLTAGE SWING (V)
VS = ±5V
OUTPUT VOLTAGE STEP (V)
5
3
Output Voltage Step vs
Settling Time, AV = 2
Slew Rate vs Temperature
VS = ±5V
TA = 25°C
–35 RL = 1k
f = 1MHz
AV = 10
–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 • TPC23
LT1187 • TPC22
Small-Signal Transient Response
AV = 2, RFB = 1k, OVERSHOOT = 25%
Small-Signal Transient Response
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
S/D
V+
7
+
– LT1187
1
+/REF
8
–/FB 4
6
V IN
VOUT
5
3
2
7
+
– LT1187
AV = +
6
1
+/REF
8
–/FB 4
V–
RFB
RG
V+
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)
VOUT
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
7 V+
RFB + RG
RG
6
S/D
VIN DIFF
VIN
3
2
5
S/D
V+
7
+
– LT1187
1
+/REF
8
–/FB 4
6
3
2
VIN DIFF
VOUT
V IN
5
V+
7
+
– LT1187
1
+/REF
8
–/FB 4
RG
V–
RFB
RFB
Q1
6
VOUT
3
+
RS
V–
RFB
2
–
RS
Q2
RE
1.1k
345mA
Q3
+
1 REF
RREF
Q4
8
RG
RE
1.1k
350mA
4 V–
RG
VO = (VIN DIFF + VIN)
RFB + RG
RG
VO =
(
RFB + RG
RG
(
VIN DIFF –
RFB
(R (
G
ILT1187 • F01
VIN
LT1187 • AI01
Figure 1. Simplified Input Stage Schematic
1187fa
8
LT1187
APPLICATIONS INFORMATION
Small-Signal Transient Response
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
CLOSED-LOOP VOLTAGE GAIN (dB)
9
8
7
CFB = 0pF
AV = 2, WITH 8pF FEEDBACK CAPACITOR
LT1187 • AI05
6
5
Extending the Input Range
CFB = 5pF
4
3
CFB = 10pF
2 VS = ±5V
T = 25°C
1 AA = 2
V
0 RFB = 900Ω
RG = 900Ω
–1
100k
1M
10M
FREQUENCY (Hz)
100M
LT1187 • AI03
Small-Signal Transient Response
AV = 2, OVERSHOOT = 25%, RFB = RG = 1k
LT1187 • AI04
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 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.
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.
1187fa
9
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
(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
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 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
LT1187 • AI08
1187fa
10
LT1187
APPLICATIONS INFORMATION
1.5MHz Square Wave Input and Equalized Response
Through 1000 Feet of Twisted-Pair
Multiburst Pattern Passed Through
1000 Feet of Twisted-Pair
LT1187 • AI09
LT1187 • AI10
Bi-Directional Video Bus
TRANSMIT 1
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
75Ω
6
75Ω
2
+
5
–
LT1187
+
–
R
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
LT1187 • AI11
1187fa
11
LT1187
SIMPLIFIED SCHEMATIC
VBIAS
+
3
–
2
+
VBIAS
7 V+
+
CM
CFF
+V
6 VOUT
+V
*
4 V–
5
S/D
1 +/REF
8 –/FB
* SUBSTRATE DIODE, DO NOT FORWARD BIAS
LT1187 • SS
1187fa
12
LT1187
PACKAGE DESCRIPTION
J8 Package
8-Lead CERDIP (Narrow .300 Inch, Hermetic)
(Reference LTC DWG # 05-08-1110)
CORNER LEADS OPTION
(4 PLCS)
.023 – .045
(0.584 – 1.143)
HALF LEAD
OPTION
.045 – .068
(1.143 – 1.650)
FULL LEAD
OPTION
.005
(0.127)
MIN
.405
(10.287)
MAX
8
7
6
5
.025
(0.635)
RAD TYP
.220 – .310
(5.588 – 7.874)
1
2
.300 BSC
(7.62 BSC)
3
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
1187fa
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
1
2
3
4
.255 ± .015*
(6.477 ± 0.381)
.300 – .325
(7.620 – 8.255)
.008 – .015
(0.203 – 0.381)
(
+.035
.325 –.015
8.255
+0.889
–0.381
)
.045 – .065
(1.143 – 1.651)
.130 ± .005
(3.302 ± 0.127)
.065
(1.651)
TYP
.100
(2.54)
BSC
.120
(3.048) .020
MIN
(0.508)
MIN
.018 ± .003
(0.457 ± 0.076)
N8 1002
NOTE:
1. DIMENSIONS ARE
INCHES
MILLIMETERS
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
1187fa
14
LT1187
PACKAGE DESCRIPTION
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
NOTE 3
.045 ±.005
.050 BSC
8
.245
MIN
7
6
5
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
1
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
× 45°
(0.254 – 0.508)
.008 – .010
(0.203 – 0.254)
3
4
.053 – .069
(1.346 – 1.752)
.004 – .010
(0.101 – 0.254)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
NOTE:
1. DIMENSIONS IN
2
.014 – .019
(0.355 – 0.483)
TYP
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)
.050
(1.270)
BSC
SO8 0303
1187fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LT1187
RELATED PARTS
PART NUMBER
DESCRIPTION
LT1189
Low Power Video Difference Amplifier
LT1193
Adjustable Gain Video Difference Amplifier
LT1194
Gain = 10 Video Difference Amplifier
LT1206
250mA Out, 900V/µs, 60MHz CFA
LT1354
1mA, 12MHz 400V/µs Op Amplifier
LT6552
3.3V Video Difference Amplifier
LT6559
Low Cost 5V/±5V Triple Video Amplifier with Shutdown
1187fa
16 Linear Technology Corporation
LT 1006 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 1993
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