gain change from bread board to pref board

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holden c

Joined Jan 23, 2014
19
i have the attached circuit whit following values:
R1=20 k ohm, R2=200 k ohm, R3= 100 M ohm, and R4= 1 G ohm resistor,
my overall gain should be R3/R4 for the fist stage and R2/R1 for the second stage. And total of 0.1*10=1.

the purpose of circuit is to amplify tunneling current which is in the order of nano amp (that is why i have very high value for R4)

i made the circuit on a bread board and it works totally fine but when i transfer everything to a pref board, my gain decreases from one to about 0.3. (the output voltage fluctuates)

I have cleaned the soldering borders with razor blade and clean everything with ethanol to make sure i don't have any mis-connection.

Any idea why i have this weird problem?
 

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