Our sensor(capacitance is around 1300pF) output current is very low(low light detection) around 1 to 10 micro amperes..
I tried with standard TIA design but due to very low level of current, it is mixing up with noise and I am unable to differentiate with noise..
I have tried the circuit referred in LTC6244 datasheet(bootstrap technique.. Fig 6a).. But the opamp is oscillating or saturating.. No signal is seen..
OPAmp used is OPA656
Feedback capacitor replaced with 0.5pF.
What could be the problem.???.
OPAmp inverting pin is not at virtual ground. At Gate of BF862, 5V is observed.. (At this time opamp is saturating)
Sensor capacitance is around 1300pF. How I can analyse the circuit?? Please provide me the detailed analysis of the circuit... How to calculate feedback capacitance when capacitance of sensor varies or If feedback resistor varies??
[edited by: bhavani at 11:16 AM (GMT -5) on 9 Feb 2021]