I am building a 9 V battery-powered microphone pre-amplifier and I'm encountering a design problem which I don't know how to solve.
I have an op-amp that serves as main amplifier which is powered by a battery using a ground and 9 V rail. In the context of this question I think this circuit is sufficient to explain my situation (values are not accurate and circuit is not complete):
My main problem is that whenever I close SW1 to turn on the device, I get a loud pop sound at the output because C4 is not yet charged (at least that's what my simulation is telling me).
I'd prefer to use the smallest circuit possible and a circuit with very low quiescent currents. There are two ways I've considered:
- Somehow make the main amplifier supply rise very slowly when SW1 is closed
- Somehow short R5 when the device is turned on. I've considered using an n-channel MOSFET, but I'm not sure if I can reliably make sure it's always shorting R5 fast enough.
Would one of these be the way to solve this and if so, what would a circuit look like?
I've also looked at this question. Since I'm not hooking up a speaker: Would disconnecting my output ground using a MOSFET work like in answer 1? Unfortunately I don't understand answer 2 at all.