I need to design a over voltage protection circuit. I intend to use a comparator for the said circuit. The reference will be from a standard voltage ref source. While the voltage at the non-inverting terminal would be the output of voltage bus.

Now, based on the comparator truth table - if the 2 are equal the output is zero and if the Vsupply is greater than reference the output is high. Now, wouldnt small spikes in the Vsupply(to the non inv terminal) be a source of voltage corruption ? How can I ensure a smooth dc level here ?

Also, suppose I want to send the output of the comparator to 2 different MOSFETS,I understand that I cannot just supply it directly as the sourcing current of comparator might not be enough. I might have to have a driver. Would a transistor be sufficient in this case ?


1 Answer 1


Yes, you can add hysteresis using positive feedback from the comparator output.


simulate this circuit – Schematic created using CircuitLab

Of course, the amount of hysteresis you add depends on how noisy you expect your signals to be.

  • 1
    \$\begingroup\$ Adding small capacitors might also help to smooth the voltages. \$\endgroup\$
    – Arsenal
    Oct 29, 2015 at 12:07
  • \$\begingroup\$ R1 is superflous here. \$\endgroup\$ Oct 29, 2015 at 12:17
  • \$\begingroup\$ what do you mean superflous ? \$\endgroup\$
    – Board-Man
    Oct 29, 2015 at 12:18
  • 2
    \$\begingroup\$ It's not doing anything. It could just be a wire. The important components are R2 and R3 \$\endgroup\$
    – Icy
    Oct 29, 2015 at 12:19

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