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LT1192CN8#PBF

P1-P3P4-P6P7-P9P10-P12
7
LT1192
Small-Signal Transient Response
TEMPERATURE (°C)
–50
300
SLEW RATE (V/µs)
400
500
600
–25 125
LT1192 • TPC19
0 25 50 75 100
V
S
= ±5V
T
A
= 25°C
R
L
= 1k
V
O
= ±2V
+SLEW RATE
–SLEW RATE
SETTLING TIME (ns)
20
–4
OUTPUT VOLTAGE STEP (V)
–2
2
4
40 160
LT1192 • TPC20
60 80 100 120 140
1mV
1mV
10mV
10mV
V
S
= ±5V
T
A
= 25°C
R
L
= 1k
0
SETTLING TIME (ns)
50
–4
OUTPUT VOLTAGE STEP (V)
–2
2
4
200
LT1192 • TPC21
100 150
0
V
S
= ±5V
T
A
= 25°C
R
L
= 1k
1mV
10mV
1mV
10mV
Output Overload
Large-Signal Transient Response
Slew Rate vs Temperature
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Output Voltage Step
vs Settling Time, A
V
= –5
Output Voltage Step
vs Settling Time, A
V
= 5
LT1192 • TPC22
A
V
= 5, C
L
= 10pF SCOPE PROBE
LT1192 • TPC24
A
V
= 10, V
IN
= 1.2V
P-P
LT1192 • TPC23
A
V
= 5, SMALL-SIGNAL RISE TIME,
WITH FET PROBES
APPLICATIO S I FOR ATIO
WUUU
Power Supply Bypassing
The LT1192 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. A
scope photo of the amplifier output with no supply by-
passing is used to demonstrate this bypassing tolerance,
R
L
= 1k.
In most applications, and those 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. Two oscilloscope photos with different
bypass conditions are used to illustrate the settling time
characteristics of the amplifier. Note that although the
output waveform looks acceptable at 1V/DIV, when
No Supply Bypass Capacitors
LT1192 • TA04
A
V
= – 5, IN DEMO BOARD, R
L
= 1k
8
LT1192
APPLICATIO S I FOR ATIO
WUUU
LT1192 • TA05
SETTLING TIME TO 1mV, A
V
= –1
SUPPLY BYPASS CAPACITORS = 0.1µF
V
OUT
1V/DIV
V
OUT
1mV/DIV
0V
LT1192 • TA06
SETTLING TIME TO 1mV, A
V
= –1
SUPPLY BYPASS CAPACITORS = 0.1µF + 4.7µF TANTALUM
V
OUT
1V/DIV
V
OUT
1mV/DIV
0V
Settling Time Poor Bypass
Settling Time Good Bypass
ampli
fied to 1mV/DIV the settling time to 1mV is 4.132µs
for the 0.1µF bypass; the time drops to 140ns with multiple
bypass capacitors.
Cable Terminations
The LT1192 operational amplifier has been optimized as a
low cost video cable driver. The ±50mA guaranteed output
current enables the LT1192 to easily deliver 7.5V
P-P
into
100Ω, while operating on ±5V supplies or 2.6V
P-P
on a
single 5V supply.
When driving a cable it is important to terminate the cable
to avoid unwanted reflections. This can be done in one of
two ways: single termination or double termination. With
single termination, the cable must be terminated at the
receiving end (75Ω to ground) to absorb unwanted
energy. The best performance can be obtained by double
termination (75Ω in series with the output of the ampli-
fier, and 75Ω to ground at the other end of the cable). This
termination is preferred because reflected energy is
absorbed at each end of the cable. When using the double
termination technique it is important to note that the
signal is attenuated by a factor of 2, or 6dB. For a cable
driver with a gain of 5 (op amp gain of 10) the –3dB
bandwidth is 56MHz with only 0.25dB of peaking.
Using the Shutdown Feature
The LT1192 has a unique feature that allows the amplifier
to be shut down 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 15kΩ in parallel with the feedback resis-
tors. The amplifiers must be used in a noninverting con-
figuration for MUX applications. In inverting configura-
tions the input signal is fed to the output through the
feedback components. When the output is loaded with as
little as 1kΩ from the amplifier’s feedback resistors, the
amplifier shuts off in 400ns. This shutoff can be under the
control of HC CMOS operating between 0V and –5V.
0V
0V
9
LT1192
Closed-Loop Voltage Gain vs Frequency
Small-Signal Transient Response
Output Shutdown
FREQUENCY (Hz)
CLOSED-LOOP VOLTAGE GAIN (dB)
24
1G
LT1192 • TA10
100M10M1M100k
A
V
= 10
A
V
= 5
22
20
18
16
14
12
10
APPLICATIO S I FOR ATIO
WUUU
LT1192 • TA08
1MHz SINE WAVE GATED OFF WITH
SHUTDOWN PIN, A
V
= 10, R
L
= 1k
LT1192 • TA09
A
V
= 10, SMALL-SIGNAL RISE TIME, WITH FET PROBES
V
OUT
–5V
0V
V
SHDN
The ability to maintain shutoff is shown on the curve
Shutdown Supply Current vs Temperature in the Typical
Performance Characteristics section. At very high
elevated temperatures it is important to hold the SHDN pin
close to the negative supply to keep the supply current
from increasing.
Operating with Low Closed-Loop Gains
When using decompensated amplifiers it should be real-
ized that peaking in the frequency domain, and overshoot
and ringing in the time domain occur as closed-loop gain
is lowered. The LT1192 is stable to a closed-loop gain of
5, however, peaking and ringing can be minimized by
increasing the closed-loop gain. For instance, the LT1192
peaks 5dB when used in a gain of 5, but peaks by less than
0.5dB for a closed-loop gain of 10. Likewise, the overshoot
drops from 50% to 4% for gains of 10.
Murphy Circuits
There are several precautions the user should take when
using the LT1192 in order to realize its full capability.
Although the LT1192 can drive a 50pF load, isolating the
capacitance with 20Ω can be helpful. Precautions prima-
rily have to do with driving large capacitive loads.
Other precautions include:
1. Use a ground plane (see Design Note 50, High Fre-
quency Amplifier Evaluation Board).
2. Do not use high source impedances. The input capaci-
tance of 2pF, and R
S
= 10k for instance, will give an
8MHz –3dB bandwidth.
3. PC board socket may reduce stability.
4. A feedback resistor of 1k or lower reduces the effects of
stray capacitance at the inverting input.
P1-P3P4-P6P7-P9P10-P12

LT1192CN8#PBF

Mfr. #:
Buy LT1192CN8#PBF
Manufacturer:
Analog Devices Inc.
Description:
High Speed Operational Amplifiers Ultra Hi Speed Op Amp
Lifecycle:
New from this manufacturer.
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