Dear all, I also have tried to build this circuit. Its not working. I have used IRF 9540 which is p-channel MOSFET in place of J176. And instead of LM358 I have used TLV2374 which is a R-R opamp. Also I have not used a POT, instead I have fixed the resistor value 10K. Rest of the circuit is all same. Can any one help me out in correcting the circuit and make it work.