[sdiy] Power Supply Anecdotal Story

[Arthur Harrison]

For most 7912s, use an output capacitor of 1uF, solid tantalum.
For most 7812s, use an output capacitor of 0.1uF, ceramic.

Remember that the capacitance at the output of a regulator must
be considered more than just a bypass for noise, they also alter
the response of the regulator's internal feedback loop, which can
oscillate if the load reactance (including the output capacitor)
provides the right conditions.

Art Harrison
e-mail:  theremin1 at att.net
pages:  http://home.att.net/~theremin1


----- Original Message ----- 
From: "Scott Gravenhorst" <music.maker at gte.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, October 20, 2001 1:41 PM
Subject: [sdiy] Power Supply Anecdotal Story


> Previous to today, I was powering my nonlinear feedback filter
> from a bench supply.  I built the power supply for it and had
> noise on -V.  Tried a bypass cap.  WORSE.  I measured what 
> initially looked like 'grass' at over 2 volts of sawtooth with 
> a 6 microsecond period.  I replaced the 7912 regulator, (with 
> one from a different mfr) and it's nice and quiet now.  On with 
> more filter testing...
> 
> =========================================================  
> - Government: The other religion.
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> 
> -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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> 
> 
>