gain change from bread board to pref board

Discussion in 'General Electronics Chat' started by holden c, Jan 25, 2014.

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  1. holden c

    Thread Starter New Member

    Jan 23, 2014
    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?
  2. bertus


    Apr 5, 2008
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