I was searching for the most simple LED flashing circuit. On a webpage (http://cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html) I found the following circuit with a transistor and a capacitor.

LED blinking circuit

As I read the description to the circuit, I was wondering, if it would be possible to swap the transistor with a z-diode, because the z-diode also uses the avalanche effect like the transistor in the circuit.

Would the ciruit below work ? And if yes, how would you have to calculate the values for the z-diode and the capacitor ?


simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ Do you really mean an enormous 330 F for C1? \$\endgroup\$ – Leon Heller Aug 20 '18 at 16:19

No, your circuit will never work with the ordinary Zener diode and low supply voltage. You need a tunnel diode or NPN transistor or some other negative resistance two-terminal device. Because the negative resistance region is the key here.

And this circuit will not work with all NPN transistor and will never work with PNP transistors.

To reduce the risk of failure builds a different circuit that uses a classic multivibrator. Because the original circuit is very fussy and for sure will not work with such a low supply voltage.


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