Zener regulated supplies

[rsumperl]

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


Thanks,
Ray

 

[Mooly]

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

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

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

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]

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

 

[DF96]

You probably already know this, but as nobody has said it, I will say it. Don't forget to include a series resistor to limit zener current i.e. don't just put a zener across the output from a bridge unless you are very sure of the resistance already supplied by the transformer.

Sorry if I'm stating the obvious.