I designed a comparator that sets 12 V on the output whenever there is overvoltage on the input of the comparator (13 V from AC sin source). In my schematic, the output value of the SR latch reacts to overvoltage but only when the voltage is above 12 V. I want to set the output of the SR latch with NOR gates permanently "HIGH" whenever the first overvoltage comes to SET gate and set the output low only when reset is "HIGH". What should I change to make it work like the diagram below?


Simulation Simulation

Diagram how I want SR latch to work Diagram how I want SR latch to work

  • \$\begingroup\$ Where is your reset signal supposed to be coming from? The way you have it now, it automatically resets the latch. \$\endgroup\$
    – vir
    Commented Nov 26, 2023 at 22:58
  • \$\begingroup\$ @vir yes, in my schematic it is connected wrongly. It should be coming from external button \$\endgroup\$
    – Simplifier
    Commented Nov 26, 2023 at 23:15
  • 2
    \$\begingroup\$ Remove the inverter, output from comparator to Set input, button to Reset input. During startup you have to generate temporary High pulse to Reset (just once at begining). Or press Reset button right after circuit become supplied. \$\endgroup\$ Commented Nov 26, 2023 at 23:38

1 Answer 1


I removed the inverter and added an extra voltage pulse source which is working as the external reset button. The source resets the SR NOR latch immediately after the start of the simulation and every 35 ms to check latch proper functionality.

Schematic Schematic

Simulation Simulation

  • \$\begingroup\$ is this the answer to your question? \$\endgroup\$
    – jsotola
    Commented Nov 27, 2023 at 1:11

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