I´ve read that the zener diodes are used for voltage regulation, and the resistor in this circuit limits the current through the diode and drops the excess voltage when the diode is conducting.

circuit with zener diode

Does that mean the voltage across R2 will be very close to 0 when the zener is not in breakdown region with the appropiate load, like in this picture??

voltage across zener diode and serie resistor

If the load conected in parallel with the zener diode is more complex, like on this other circuit, will the combination of the resistor and zener diode behave the same way?

circuit with different load

  • \$\begingroup\$ How old is this circuit you've drawn here? Can you even get UJTs anymore? \$\endgroup\$
    – Hearth
    Oct 22, 2020 at 1:22

1 Answer 1


No, because the load current also flows through R2, and that happens all the time — even when VZ is not conducting.


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