Charge feedthrough in analog MOS switches has been measured. The dependence of the feedthrough voltage on the input and tub voltages, device dimensions, and load capacitances was characterized. Most importantly, it was observed that the feedthrough voltage decreases linearly with the input voltage. The significance of this observation when considering harmonic distortion in sample-and-hold circuits is discussed. A first-order computer simulation based on the quasi-static small-signal MOSFET capacitances shows good agreement with experimental results.