Is it possible to turn off an SCR by applying a negative pulse to its gate?
No, the SCR once triggered can only be turned off in two ways:
a) Interrupting the current that feeds its circuit. This can be done by turning off the power supply for a moment.
b) By causing the voltage between its anode and its cathode to fall to zero, which also corresponds to interrupting the current in the device. This can be done by connecting a pressure switch between the anode and the cathode.
There are special SCRs, called GTOs (Gate Turn-off Operated SCRs) that can be shut down by the gate, but are still little used and difficult to find.
