7820 regulator source...?

[Gene Zumchak]

Rob,

    Quiescent current for a 78XX is about 3 ma.  If you connect about a 1.6K
resitor from a 7815 ground pin to ground, you'll drop about 5 volts across the
resistor and the regulator will ride on a five volt pedestal.  Bypassing the
resistor won't hurt.  If you were doing this for a lot of systems, you would
use a smaller resistor and connect another resistor from the output to the
ground lead.  This provides 15/R of current.  If this is few times larger than
3mA, then the output will be less dependent on the quiescent current.

Gene Z.



Rob Hukin wrote:

> Anyone know of a source for these 20V regulators? Slightly off topic
> (apologies) but it's for an old Revox B77 and good old Revox want to charge
> me 15ukp for one!
>
> rob.