[sdiy] Clean Power Supplies

Tim Ressel madhun2001 at yahoo.com
Tue Aug 20 08:03:17 CEST 2002


Glen,

Any pass-transistor (series) style regulator will have
good noise characteristics, because the pass
transistor acts as a capacitance multiplier. In fact,
one can add little series-pass transistors to the
power supply pins of an opamp to improve PSRR. Its
something like the capacitance on the base gets
multiplied but the beta of the transistor.

The layout of the circuit, both electrical and
physical, will have an impact on regulator
performance. I have had good luck with 7815/7915s, as
long as I make beefy grounds and good bypassing. For
reference voltages (+/-10V), I use a LT1021 feeding an
opamp with a drive transistor on the output. Quiet and
precision, hust the way I like it.

--TR

--- Glen <mclilith at ezwv.com> wrote:
> I've been wondering, which voltage regulators have
> the least amount of noise? I
> know we can discard most switch mode supplies, as
> being relatively high noise
> devices. So then, which analog regulator would give
> the absolute least noise
> for common audio circuitry like op-amps?
> 
> In addition to figuring out which regulator chip or
> circuit to use, one of my
> gut feelings is to avoid regulator circuits with a
> potentiometer adjustment,
> because the pot will eventually become a poor
> connection, and your supply
> voltage will become noisy. Likewise, I would limit
> my use of mechanical
> connectors, preferring to solder connections when
> possible. 
> 
> 
> 
> later,
> Glen


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