Op-Amps based schmitt trigger with controllable threshold voltage and its application to voltage-to-period converter

In this paper, a simple Schmitt trigger circuit with controllable threshold voltage consisted of a voltage comparator circuit and controllable unity-gain inverting/non-inverting amplifier is presented. The DC-transfer characteristics of the proposed circuit is in the form of voltage controllable Schmitt trigger. The configuration of the proposed circuit comprises basic commercially available devices such as operational amplifiers (op-amps), analog switch and resistors. The performance of the proposed approach confirmed by experimental results indicates that the proposed Schmitt trigger circuit can function effectively and agree with the expected value. In addition, the application of the proposed scheme implemented to a voltage-to-period converter and its experimental results are also included.