LT1192CS8 查看數據表（PDF） - Linear Technology

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LT1192CS8

Ultrahigh Speed Operational Amplifier

Linear Technology 

LT1192

APPLICATIO S I FOR ATIO

amplified 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.

Settling Time Poor Bypass

Double Terminated Cable Driver

5V

3+

7

6

75Ω CABLE

2

LT1192

–4

RG

–5V

RFB

75 Ω

VOUT 0V

1V/DIV

0V

VOUT

1mV/DIV

Cable Driver Voltage Gain vs Frequency

24

TA = 25°C

20

AV = +5

16

RFB = 910Ω

RG = 100Ω

AV = +10

RFB = 910Ω

RG = 47Ω

12

8

SETTLING TIME TO 1mV, AV = –1

SUPPLY BYPASS CAPACITORS = 0.1µF

LT1192 • TA05

Settling Time Good Bypass

VOUT 0V

1V/DIV

VOUT

0V 1mV/DIV

LT1192 • TA06

SETTLING TIME TO 1mV, AV = –1

SUPPLY BYPASS CAPACITORS = 0.1µF + 4.7µF TANTALUM

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 7.5VP-P into

100Ω, while operating on ±5V supplies or 2.6VP-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

4

0

100k

1M

10M

FREQUENCY (Hz)

100M

LT1192 • TA07

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.

8

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