the diode thingy is use to supply the OP-AMP AND also use to modulate the OP-AMP signal to the supply line. I don't know how the RCX handle it but to me , for your application it's way too complicated.


Now if you want to use this grand'pa 16F84, you will need to boost the MIC signal. A single rail op-amp will do the job.

Did you already know which mic model you will use?