Channel charge compensation switch with first order process independence.

摘要

Channel charge compensation is achieved in a MOS switch comprising two MOSFETs (20, 22) connected in parallel and a compensating MOSFET (24) placed on the semiconductive substrate in precise symmetry with the two switching FETs, each of the FETs being designed to have the same channel charge storing capacity. Accordingly, first order variations in oxide thickness or in gate width across the surface of the semiconductive substrate do not affect the accuracy with which channel charge is compensated in the invention. The compensating FET is switched in complementary fashion with the two switching FETs so that it absorbs one-half of the channel charge expelled from the switching FETs when they are turned off; thus preventing this charge from upsetting other components in the circuit such as precision storage capacitors connected to the switch.