ABSTRACT
Extensions on the sample and hold application of analog switches include peak detectors, voltage to frequency converters, switched-capacitor filters, and time-division multiplexed systems, to name a few. This chapter looks at analog switch applications in sampled-data systems such as the above. It focuses on the basic sample and hold function, examines ways to optimize S/H performance for differing applications. Body snatchers are additional MOSFETs in a CMOS switch output stage that are often included inside the switch to compensate for switch leakage and ON resistance modulation that results from the body effect. The cause of the glitch is the difference in turn-ON time between the body snatcher and the switch Field Effect Transistor. Leakages in the analog switch will cause droop rate errors as the leakage current charges/discharges the hold capacitor. The input buffer presents the previous stage with a high impedance, so that there will be no losses due to the loading of a low ON-resistance switch.
