[sdiy] DC blocking caps on inputs - or not?

[Neil Johnson]

Mattias Rickardsson wrote:
> There isn't any voltage over a DC-blocking cap unless you are in the
> low frequency range where it actually blocks DC.

What about circuits where there really is  DC bias if some sort?
E.g., microphone pre-amp might see 48V phantom power, or a modern
audio DAC might bias the outputs at half-Vref?

> So if you don't
> expect a DC-offset situation, and keep the cap big enough to pass all
> the expected signal, then it doesn't matter much that the cap is
> polar, and its marked voltage doesn't matter much either - it could
> even be less than your expected signal swing.

You also need to think about what happens to op-amp outputs during
turn-on - they can hit the rails and stay there for quite some time
before the loop closes.

Neil
--
http://www.njohnson.co.uk