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I have a logic circuit currently consisting a few few AND gates and it's working fine (simulating) with if i use logic levels as the inputs. However my input levels might change in amplitude and I'd like to be able to control the logic threshold with something else (like and DAC or something). What would be the simplest way to do this?

if it helps, my inputs are very short pulses, that should have the same amplitude, although the amplitude may very from time to time.

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  • \$\begingroup\$ Why might your logic levels change? It's better to fix your logic levels so that they don't change unless there's some very good reason for it. And I can't think of any. \$\endgroup\$
    – Hearth
    Commented Oct 26, 2018 at 21:31
  • \$\begingroup\$ that should have the same amplitude, although the amplitude may very from time to time. - the two statements are contradictory. \$\endgroup\$
    – Eugene Sh.
    Commented Oct 26, 2018 at 21:42
  • \$\begingroup\$ How much do you expect these input amplitudes to vary? 0.01 V to 500 V is a whole different problem than 4.5 to 5.5 V. \$\endgroup\$
    – The Photon
    Commented Oct 26, 2018 at 21:44
  • \$\begingroup\$ the input isn't coming from a logic device, but rather it's an analog pulse. I'm not actually sure how much it's going to vary, but shouldn't be more than 3V. \$\endgroup\$ Commented Oct 26, 2018 at 22:08
  • \$\begingroup\$ Use an opamp to turn the analog into a digital pulse? \$\endgroup\$
    – mike65535
    Commented Oct 26, 2018 at 22:15

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Bring your input signals into suitably fast comparators. Run each input signal to the '+' input of a comparator, and run a reference voltage from a DAC output (or a good old fashioned potentiometer with a knob) to the '-' inputs of all the comparators.

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  • \$\begingroup\$ as soon as i posted i started thinking about adjusting the input to a logic level rather than trying to adjust the thresholds of the gates themselves. Thanks a bunch! \$\endgroup\$ Commented Oct 26, 2018 at 22:06

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