Sorry to bother with questions but I'm seeking a bit of guidance/help. As part of a project I'm trying to amplify the signal from a microphone (https://datasheets.maximintegrated.com/en/ds/MAX9814.pdf) by using an op-amp (LM 358). Both the op-amp and microphone are powered by the 5 V output of the Arduino, with the negative connection on the op-amp being connected to ground.
The signal being received from the microphone pre-amplification is around 0.2 - 0.3 V. I was using two resistors for a non-inverting amplification, but I'm not getting the expected results. Using identical resistors is resulting in no amplification. The op-amp 'works' when set up as a voltage follower. However, when the resistors are different (10 / 50 Ohm used and 50 /1k Ohm used, the output is 0).
I've initially assumed that the resistors were incorrectly connected, wrong way round etc... but this hasn't solved the issue. I've replaced the op-amp with another LM 358 and the problem is the same.
My next point of call would be to change the op-amp. Another port of call would be investigation into the DC-biased output of the microphone, and the impact that will have.
Any suggestions and ideas more than welcome.