Hi, I am new here. I need to build an op amp with a single supply input. I am trying to amplify a signal from 125mVrms to a nominal 1 volt pk-pk. So any help I could get regarding plans or direction for building a low power single supply op amp with a gain factor of about 5 or 6 would be awesome. Thanks.
Is your signal a normal AC bipolar signal (+/-) centered around ground? If so then you will need to couple the signal through a capacitor with the cap output going to a resistor divider connected the + supply and ground. Two 20kΩ resistors should work. The capacitor needs to be large enough to transfer the lowest signal frequency into a 10kΩ load. For 20Hz this would be 1µF or greater.
Connect the junction of the two resistors and capacitor to the op amp + (non-inverting) input.
For a nominal gain of 5.6, connect a 10kΩ resistor from the - (inverting) input to ground and also connect a 46kΩ resistor from the op amp output to the - input.
The output voltage will have a DC offset of 1/2 the supply voltage. If you need the output referred back to +/- ground level, you will need to add a capacitor at the op amp output.