Voltage comparators with electrical variable hysteresis and applications

This paper describes the issues and tradeoffs in the design and monolithic implementation of the voltage comparators with electrical variable hysteresis (VCEVH). The increasing trend to integrate information acquisition and digital processing on the same chip determines increasing number of functions for typical electronic circuits. We propose two variants of VCEVH for bipolar and unipolar applications. These circuits use a voltage controlled current source to control the width of the hysteresis cycle. The output current of the current source is switched by the optically coupled isolators or by bipolar transistors. This current is applied to a resistor and the voltage across the resistor controls the width of the hysteresis cycle. The circuits can be made as integrated circuits. Finally, we present a voltage to time period linear converter which uses these types of comparators. The results are confirmed experimentally