Patent ID: 6157222
Filing Date: 2000-12-05
Classification: H03K

Abstract:
A variable threshold comparator receiving, on an input node, an input signal having a voltage, and providing an output signal on an output node when said voltage of said input signal exceeds a selectable threshold voltage of said comparator, comprising:a transistor coupled by way of its source and drain between a first polarity power supply node and an output node, and having its gate coupled to said input node;a plurality of pairs of transistors, each pair in said plurality of pairs of transistors being coupled together by a source of a first one of said each pair of transistors and a drain of a second one of said each pair of transistors, and coupled in series between said output node and a second polarity power supply node, a gate of said first one of said each pair of transistors coupled to said input node, and a gate of said second one of said each pair of transistors coupled to a control signal specific to said second one of said each pair of transistors;wherein said threshold voltage of said comparator is selectable by the application of one or more of said control signals to a respective one or more of said second ones of said each pair of transistors; anda calibration sequencer, said calibration sequencer comprising:a reference voltage source, for use as a temporary substitute for said input signal;means for automatically sequencing different selections of said control signals while monitoring said output signal;means for determining and holding an optimum selection of said control signals; andmeans for continuing to provide said optimum selection of said control signals, while removing said reference voltage such that said input signal may be applied to said input node.