LT1194 查看數據表（PDF） - Linear Technology

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LT1194

Video Difference Amplifier

Linear Technology 

LT1194

APPLICATIO S I FOR ATIO

A scope photo of the amplifier output with no supply

bypassing is used to demonstrate this bypassing toler-

ance, RL = 1k.

In many 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 ampli-

fied to 10mV/DIV the settling time to 10mV is 200ns. The

time drops to 162ns with multiple bypass capacitors, and

does not exhibit the characteristic power supply ringing.

Settling Time Good Bypass

LT1194 • TA07

SETTLING TIME TO 10mV,

SUPPLY BYPASS CAPACITORS = 0.1µF + 4.7µF TANTALUM

No Supply Bypass

IN DEMO BOARD, RL = 1k

LT1194 • TA05

Settling Time Poor Bypass

Cable Terminations

The LT1194 video difference amplifier has been optimized

as a low cost cable driver. The ±50mA guaranteed output

current enables the LT1194 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 en-

ergy. The best performance can be obtained by double

termination (75Ω in series with the output of the amplifier,

and 75Ω to ground at the other end of the cable). This

termination is preferred because reflected energy is ab-

sorbed 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 (LT1194 gain of 10), the –3dB bandwidth is over

30MHz with no peaking.

SETTLING TIME TO 10mV,

SUPPLY BYPASS CAPACITORS = 0.1µF

LT1194 • TA06

A Voltage Controlled Current Source

The LT1194 can be used to make a fast, precise, voltage

controlled current source. The LT1194 high speed differ-

ential amplifier senses the current delivered to the load.

The input signal VIN, applied to the (+) input of the LT1191,

8

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