Can anyone help me with this amplifier circuit?

The circuit given as attachment is a current to voltage converter designed to convert input current of pA range to voltage and to amplify it so that the output voltage is within a measurable range of 0-10V.The pA current input is given to LMC662CN by connecting mV source in series with 1 GigaOhm resistance

I tried this circuit on PCB but it is giving a constant output voltage of 10.722V.The output remains as such even if you remove the input voltage of mV range.

Can anyone please tell me what could be wrong?

Where did you find a 1 gig ohm resistor?

Trouble shoot:
Each IC should have a +12V and a -12V.
IC2 output is stuck at +10. What is IC1 output at? Is it at -10V?

You're working with extreme gains. Any slight offset on the input will swing the output from rail to rail. (+10v to -10v). If the circuit is built properly, ground your input source and see if R6 will allow you to set your zero on the output. If not, you have a wiring error. Because of the extreme gain, even breathing on the circuit can cause the output to swing wildly. Any leakage around the first IC will cause problems too. One possible solution is to swap the two stages. The input impedance of the OP-07 as drawn is relatively low (100 ohms) so if you are worried about loading, change the input and feedback resistors to 100k and 1meg respectively. reversing the two stages will allow you to set your zero point first and then make your gain as needed. You can also study some basic op-amp info here: https://www.neatcircuits.com/op_amp.htm

Radioman913 said:

You're working with extreme gains.https://www.neatcircuits.com/op_amp.htm

Click to expand...

What? Maybe current gain but not voltage gain. IC1 gain=1, IC2 gain=10

I can't even make much sense of the circuit, the image is too grainy.

It may just be a buglet. But any leakage from the input to either of the positve voltages would have the same effect. Is the board squeeky clean after soldering?

Until I get the voltage on every pin of both ICs I can not trouble shoot.
"Doctor I don't feel good. Whats wrong?" From 2000 miles away I can see your left kidney is where your leg should be.

Oops! You're right. I thought the input resistor was much lower. In this case if he was looking for a very high input impedance, he should just make the first stage a follower. Tie pins 1 + 2 together, pin 3 should have the *1 gig* resistor going to ground and feeding the source directly to pin 3.