This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

OPA2134: Setting the gain of a preamplifier for MEMS microphone

Part Number: OPA2134
Other Parts Discussed in Thread: TL072,


I'm using TI's OPA2134 and TL072 OpAmps to amplify the audio signal from a MEMS microphone. Schematic and board designs are here.  I am looking for very high gain; R2 is a 100K pot; I expect R2/R1 to be the gain for the 1st channel of this preamp. JP1 and JP2 are this MEMS microphone breakout board, and IC3 is a 5V regulator for powering the MEMS microhpone breakout board.  The battery is a 12V A27.

My questions are:

1) I find the circuit doesn't work unless the R2 pot is turned to its highest setting, no matter what the value of this pot is.  I've tried a 10K, 20K and 100K pot; all appear to produce the same gain, and only work at their highest setting.  How do I get better/variable gain out of this design?
2) Are there better (higher gain, lower noise, lower power consuption) ICs for this task? 
3) How can I reduce the power consumption of this board to allow for longer battery life?

Thank you,