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.