Can anyone plz tell me how to calculate internal impedance of a circuit?

[LvW]

Oh no.The input resistance was 1Gohm at the inverting input.Supply was given to pins 4 and 8(V- and V+ pins)

Hi anushaas,
I don't know if it is still interesting for you, but I have discovered a new article in EDN magazine dealing with the measurement of small currents. Here is the link:

**broken link removed**

Perhaps it supports your investigations.
Regards
LvW

 

[FvM]

I'm unable to relate the simulation results to the previous postings. The simulation shows all in all normal operation, the previous post told about circuit failure. Do you mean, that the real hardware doesn't behave according to the simulation?