CMOS voltage comparator with internal hysteresis

Claim 1

A CMOS comparator with internal positive current feedback for generating hysteresis in the switching of the output voltage signal as a function of the input voltage signal, said comparator comprising: a transconductance amplifier for generating a current through a first insulated gate field effect transistor which is a function of voltage at its input, said first insulated gate field effect transistor having its source connected to a first potential terminal and having its drain connected to a common junction terminal; a second insulated gate field effect transistor having its source to drain conduction path connected between said common junction terminal and a second potential terminal; a source of control current; means for generating a first feedback current as a function of said control current; an output terminal; an output inverter comprised of third and fourth insulated gate field effect transistors, said third transistor having its source to drain conductive path connected between said output terminal and said first potential terminal and said fourth transistor having its source to drain conductive path connected between said output terminal and said second potential terminal, said third and fourth transistors further having their gate electrodes connected to said common junction terminal; and switching means connected to said means for generating said first feedback current and to said output terminal for connecting said first feedback current in parallel with said first transistor as a function of voltage at said output terminal.