LF398M (TEXAS INSTRUMENTS)

The LF398M is a monolithic Sample and Hold Circuit utilizes 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 6µs 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 1MHz op-amps without having stability problems. P-channel junction FET's are combined with bipolar devices in the output amplifier to give droop rates as low as 5mV/min with a 1µF 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.