1 Features

1• Operates from ±5-V to ±18-V Supplies

• Less than 10-μs Acquisition Time

• Logic Input Compatible With TTL, PMOS, CMOS

• 0.5-mV Typical Hold Step at Ch = 0.01 μF

• Low Input Offset

• 0.002% Gain Accuracy

• Low Output Noise in Hold Mode

• Input Characteristics Do Not Change During Hold

Mode

• High Supply Rejection Ratio in Sample or Hold

• Wide Bandwidth

• Space Qualified, JM38510

2 Applications

• Ramp Generators With Variable Reset Level

• Integrators With Programmable Reset Level

• Synchronous Correlators

• 2-Channel Switches

• DC and AC Zeroing

• Staircase Generators

3 Description

The LFx98x devices are monolithic sample-and-hold

circuits that use BI-FET technology to obtain ultrahigh

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 LFx98x to be included

inside the feedback loop of 1-MHz operational

amplifiers without having stability problems. Input

impedance of 1010 Ω allows high-source impedances

to be used without degrading accuracy.

P-channel junction FETs 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

JFETs have much lower noise than MOS devices

used in previous designs and do not exhibit high

temperature instabilities. The overall design ensures

no feedthrough from input to output in the hold mode,

even for input signals equal to the supply voltages.

Logic inputs on the LFx98x are fully differential with

low input current, allowing for direct connection to

TTL, PMOS, and CMOS. Differential threshold is

1.4 V. The LFx98x will operate from ±5-V to ±18-V

supplies.

An A version is available with tightened electrical

specifications.