CHP Home GenChem     Analytical     Instrumentation     Index   

Silicon-Controlled Rectifier (SCR)

Introduction

SCR's are used for overvoltage protection for digital circuits.

Circuit symbol:

The SCR is normally nonconducting as long as the gate is at a lower voltage than the cathode. If the gate voltage becomes larger than the cathode voltage, then the SCR becomes a short and lets current pass from the anode to the cathode.

Circuit for overvoltage protection

If the input voltage exceeds the zener breakdown voltage of approximately 6 V, current passes through the zener diode and produces a voltage on the SCR gate. The SCR then shorts the input power supply to ground protecting the rest of the circuit.


 Top of Page   
 Copyright © 2000 by Brian M. Tissue, all rights reserved.