Switching circuitry as for a flash A/D converter

摘要

A flash type A/D converter has a plurality of transistor switch means for alternately connecting respective ones of a plurality of reference potentials or input signal to a plurality of summing capacitors each serially connected to a self biased inverter (comparator) circuit. Certain ones of the switches are configured to operate in the source follower mode to preclude excessive capacitor discharging when extremes of input signal are applied. This reduces the current required to recharge the capacitors by the reference potential source and tends to limit loading affects on the reference source. In addition certain ones of the switch transistors have their turn on or threshold potentials tailored to effectively reduce feedthrough between the respective switch control electrodes and the capacitor-switch interconnection.