Features

n Operates from ±5V to ±18V supplies

n Less than 10 μs acquisition time

n TTL, PMOS, CMOS compatible logic input

n 0.5 mV typical hold step at Ch = 0.01 μF

n Low input offset

n 0.002% gain accuracy

n Low output noise in hold mode

n Input characteristics do not change during hold mode

n High supply rejection ratio in sample or hold

n Wide bandwidth

n Space qualified, JM38510

General Description

The LF198/LF298/LF398 are monolithic sample-and-hold

circuits which utilize BI-FET technology to obtain ultra-high

dc accuracy with fast acquisition of signal and low droop

rate. Operating as a unity gain follower, dc gain accuracy is

0.002% typical and acquisition time is as low as 6 μs to

0.01%. A bipolar input stage is used to achieve low offset

voltage and wide bandwidth. Input offset adjust is accomplished

with a single pin, and does not degrade input offset

drift. The wide bandwidth allows the LF198 to be included inside

the feedback loop of 1 MHz op amps without having stability

problems. Input impedance of 1010W allows high

source impedances to be used without degrading accuracy.

P-channel junction FET’s are combined with bipolar devices

in the output amplifier to give droop rates as low as 5 mV/min

with a 1 μF hold capacitor. The JFET’s have much lower

noise than MOS devices used in previous designs and do

not exhibit high temperature instabilities. The overall design

guarantees no feed-through from input to output in the hold

mode, even for input signals equal to the supply voltages.