[sdiy] 7905 output voltage, FAQ probably

[Seb Francis]

Jason Proctor wrote:
> thanks for the response.
>
> i currently have a little circuit breadboarded up that has an opamp 
> sucking on it, and the output voltage is down to -5.7v, so it's 
> heading in the right direction. i fully expect the one that's soldered 
> in to start behaving itself when i hook it up to various things.
>
> any idea why this affects only the -ve regulator? the 7805 i wired up 
> with nothing sucking on its output gave a reliable +5.
>

This is normal in my experience - 79XX regulators need quite a lot of 
load to get within the spec'ed voltage.  78XX on the other hand seem ok 
with no load.  However the datasheets state minimum of 5mA current draw 
for either type, so could be that even some 78XX need load.

Seb