I'm attempting to create a guitar pedal using diodes to clip the audio signal and create distortion. Specifically, I'm trying to create a circuit with variable clipping by using a circuit that acts like a diode which has a variable voltage drop from around 0.7-3.5. It's also possible to use a Zener diode type circuit with a variable breakdown voltage.

I believe that the TL431 IC would serve this purpose, but the forward voltage drop is specified from 2.5-5 V, which is too high for the application. Are there any other components or circuits that perform a similar task with a lower voltage level?

Thanks in advance for any help

  • \$\begingroup\$ The TLV431 (note the V) works down to 1.25 V. Or you could do something more custom with an op amp. \$\endgroup\$
    – Hearth
    Commented May 16, 2022 at 5:40
  • \$\begingroup\$ There is such transistor circuit; its figurative name is "rubber diode" or "VBE multiplier". \$\endgroup\$ Commented May 17, 2022 at 4:37

2 Answers 2


Passive AC clipping circuit Rev2 This is a passive solution where you can control the clipping voltage by potentiometer.

  • \$\begingroup\$ Made a mistake: T2 must be PNP (e.g. BC557) \$\endgroup\$
    – Jens
    Commented May 16, 2022 at 22:08

Just use a regular diode with variable gain on the opamp. That will make the effective clipping voltage (relative to the signal voltage) variable.

Then apply more gain/attenuation as necessary.

Oh wait, that's what they all do anyway...


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