Are there any chips similar to a Schmitt trigger but with a wider high low input threshold that trigger high with 3-3.3V and low 0.1-0.2V?

I need it to alleviate switch bounce.

A comment from the Teensy forum:

You want to get it below 1.15 to be sure it reads as low, and above 2.31 to be sure it reads as high. The actual threshold is somewhere between those two, with approx 60 mA hysteresis.

I looked and I saw a circuit that can be made with an op amp. I want to know if there is a chip similar to a Schmitt trigger. Simple input-output and many inputs/outputs.

enter image description here

  • 1
    \$\begingroup\$ You should maybe explain why you can't use any stadard Schmitt trigger input device for simple switch debouncing, why do think you need a special chip with custom thresholds for that? \$\endgroup\$
    – Justme
    Oct 30, 2021 at 10:48
  • \$\begingroup\$ <<<The actual threshold is somewhere between those two, with approx 60 mA ??? hysteresis >>> .Use a CD40106 (inverter) with power supply 3.3V. You will have trigger points at ~ 0.150 V and ~ 3.1 V. Or CD4584 ? \$\endgroup\$
    – Antonio51
    Oct 30, 2021 at 11:39
  • 1
    \$\begingroup\$ A schmitt trigger is a circuit configuration, not a specific chip! For debouncing you just sample the input at a given rate and if the input has not changed for n samples, then it is considered stable. Of course you’re not using external interrupts for a switch input as that would be bad juju. \$\endgroup\$
    – Kartman
    Oct 30, 2021 at 11:41
  • \$\begingroup\$ If you insist on hardware debouncing, simply slow down the signal with an RC network and use any chip with a ST input such as 74HC14. \$\endgroup\$ Oct 30, 2021 at 13:14
  • \$\begingroup\$ Radu, two BJTs and a few resistors and you are done if you really want those thresholds. Of course, we've no idea if that's the appropriate direction. \$\endgroup\$
    – jonk
    Oct 30, 2021 at 19:20

1 Answer 1


No, there is no Schmitt trigger device that evaluates >3V to high and <0,2V to low. A Schmitt trigger is nothing else than an amplifier with positive feedback loop so you can build your circuit like that:


simulate this circuit – Schematic created using CircuitLab

The problem can also be solved with an operational amplifier, but it makes more sense to use the 4069 hex inverter.

The Hysteresis is calculated as follows: $$ Hysteresis_{} = \frac{R_1}{R_2} $$ R2 must be larger than R1. with almost equal resistors you can achieve almost 100% Hysteresis and with a R2>>R1 basically 0

e.g.: 3,3V logic R1=100k; R2=120k the Hysteresis is 0,83, the lower Voltage is ~0,11V and the upper Voltage is ~1,93.

Debouncing requires a low pass filter before Schmitt trigger input. I made good experiences with 10nF and 51kOhms. My mechanical switches bounce back and forth for about 1ms, and I found 0,5τ to 1τ perfect for debouncing.


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