Zener regulated supplies

[rsumperl]

Greetings everyone,
Do zener regulated supplies cause any "noise"? If they do, how would you "quiet" them?


Thanks,
Ray

[Mooly]

Originally Posted by rsumperl

Greetings everyone,
Do zener regulated supplies cause any "noise"? If they do, how would you "quiet" them?


Thanks,
Ray

Depends on how you are using them ?
A small 0.1uf cap across each is normally more than sufficient. Zeners produce broadband noise (very low level) in operation and can actually be used as a noise source if you amplify it as here on page 3,
http://www.n0ss.net/noise_generator_ac7ac-style.pdf

Low voltage zeners ? high voltage ? and how are you using them ? same applies though, a small cap and the noise is gone.

[rsumperl]

I'm using the zeners in a bias supply. The zeners will be regulating voltage coming from a bridge rectifier.

Ray

Originally Posted by Mooly

Depends on how you are using them ?
A small 0.1uf cap across each is normally more than sufficient. Zeners produce broadband noise (very low level) in operation and can actually be used as a noise source if you amplify it as here on page 3,
http://www.n0ss.net/noise_generator_ac7ac-style.pdf

Low voltage zeners ? high voltage ? and how are you using them ? same applies though, a small cap and the noise is gone.

[Mooly]

That's fine... a small cap kills the noise. It's standard practice.

Just make sure the zeners operated within it's ratings... current and power wise.

[rsumperl]

What's your thinking on type of cap? My local parts guy only has Polyester Mylars in stock.

Ray

Originally Posted by Mooly

That's fine... a small cap kills the noise. It's standard practice.

Just make sure the zeners operated within it's ratings... current and power wise.

[Mooly]

Polyesters fine, and so too ceramic for this. Electroylitics are no good as they offer increasing impedance at HF, even if you could get such small values.

[rsumperl]

Just to change the subject a bit, am I going overboard by using a bridge instead of a half wave?

Thanks

Originally Posted by Mooly

Polyesters fine, and so too ceramic for this. Electroylitics are no good as they offer increasing impedance at HF, even if you could get such small values.

[BinaryMike]

In most cases, because bias supply current drain is so low, there is essentially nothing to gain by using a bridge.

[atmasphere]

Originally Posted by rsumperl

Greetings everyone,
Do zener regulated supplies cause any "noise"? If they do, how would you "quiet" them?


Thanks,
Ray

Of course the cap is a good practice, but some zener diodes are light sensitive; more *or* less noisy in the presence of light. Its easily measurable if this is the case. So if they don't like light, some heatshrink will do nicely.

[Sch3mat1c]

Zeners are notoriously noisy, particularly at low current. This is completely irrelevant in a bias supply, where the voltage is high and noise doesn't matter. Keep current high, and bypass with a cap. You won't notice a thing.

Tim