[sdiy] Op Amp AC Coupling/DC Biasing (was Blocking audio at power off

[Stewart Pye]

Justin Owen wrote:
> I ended up using the schematic that Fabio provided (with a voltage divider/bias on the non-inverting input rather than just a resistor to ground).
>
> I messed around with the resistor values a bit - but it looks like the inputs want to be at VCC/4 (2.34 Volts from a supply that is sitting at about 9.38 Volts) and the output then sits at about VCC/2 (about 4.68 Volts)?
>
>   

Hi Justin,

I couldn't see the schematic that Fabio provided, but do you have a DC 
blocking cap between the resistor that goes from the inverting pin to 
ground and ground? If not it is a DC amplifier and this is why you are 
getting DC offset at the output.  I'm not sure what value resistors you 
are using, but 10uF should be ok. Calculate the low frequency cutoff by:

f = 1 / 2*pi*R*C

Cheers,
Stewart.