Zener diode application suggetions

mistermotown · Oct 29, 2012

Hi, I recently bought 10 Zener diodes the last time I purchase circuit elements. I was wondering if anyone had simple circuits or projects I could do, that needs zener diodes.

Studiot · Oct 29, 2012

How about making a white nose generator and a pink noise generator?

I don't think the classic noise diode is available any more so you have to use something like a zener.

Edit : These generators can be the basis for all sorts of sound effects.

dlgoff · Oct 29, 2012

Zener diode current sources, voltage regulators, and clippers come to mind.

AlephZero · Oct 29, 2012

This should keep you busy for a while, if you can't find ideas on the web.
http://www.amazon.co.uk/Circuits-Germanium-Silicon-Publishing-Electronics/dp/0859340392

Studiot said: ↑

I don't think the classic noise diode is available any more so you have to use something like a zener.

Reverse biasing the base-emitter junction of a low voltage BJT transsistor (pretty much any type) makes a nice "noisy" zener, with a breakdown voltage of about 5V. Probably a better noise source than a good quality "real" zener!

mistermotown · Oct 29, 2012

The noise circuits and the clipper look really interesting, and that's exactly what I was looking for! Thanks!

And that book was unavailable to ship, but I will look into getting it, it seemed pretty interesting.

Septivalian · Nov 5, 2012

The Zener diode can be used to limit a voltage on a node to its rated value! Try taking a few and seeing how de-rated the datasheet is. Diode manufacturers can deflate the robustness of their diode at times, and other times the doping is so inconsistent you could get a zener that breaks down at twice the rated voltage (like having two cheerios stuck together.)

Enthalpy · Nov 5, 2012

If your Zener have a good voltage, like 30-200V, you can see a funny effect.

Observe the (amplified) noise in the darkness. Provide light an access to the junction (saw...) and illuminate, at identical Zener current: the noise decreases sharply.

I did it to verify that the cause of noise is that charge carriers move in bunches created by avalanche multiplication. Light creates more avalanche "seeds" so each bunch gets smaller and this reduces the noise.

Consistently, heat reduces the noise, as well as a low Zener voltage. The noise sqrt(2*I*Q*B) makes also bunches of Q total charge roughly compatible with the Zener voltage.

For instance, a 5V Zener (which isn't a good Zener then, rather a Tunnel diode) has a very soft (=bad) I-V characteristic because 5V don't suffice to multiply the charge carriers much, but is very silent. Much more silent than a bandgap voltage reference. So if you want a silent voltage reference chip, say for an ADC, choose one that integrates a Zener (with the necessary compensations) and not a bandgap circuit.