Zener diode application suggetions

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.

 

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

 

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

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!

 

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.)

 

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.