Noise analysis was done using SR785. SR560 was used with a flat gain of 100 to get above the noise floor of SR785. The input range was constantly maintained at -44dBVpk for all measurements. Voltage regulators LM317 and LM337 were used to power the circuit. 200 averages were taken for all the measurements. The TIA was configured with a 5.1k feedback resistor and 100pf feedback capacitor. Please refer elog:2390 for better understanding of the circuit diagram.
** Referring to elog:2411 the 8kHz noise bump went away on its own without changing anything in the circuit. I have no clue how it happened and why it's not happening again.
Attachment 1: Noise analysis using OP27 in transimpedance amplifier. At Frequencies below 100Hz, data was taken in 4 parts, starting from 0Hz with a span of 25Hz but with 10 number of averages(fewer averages were taken only in this case). At high frequencies(above 100Hz) data was taken with 200 averages. A noise was observed to be 10pA/rtHz was observed at 10Hz and 3pA/rtHz above 300Hz.
Attachment 2: LT1792 was used in this case. It was seen that it is less noisy as compared to OP27. The noise was observed to be 2pA/rtHz above 20Hz.
Attachment 3: LT1012 was used for this measurement. The noise was observed to be 3pA/rtHz above 20Hz.
Attachment 4: AD820 was used for this case. The noise was observed to be 3pA/rtHz above 500Hz.
Attachment 5: OPA140 was used for the TIA during this measurement. The noise was observed to be 2pA/rtHz above 2Hz.
Attachment 6: Noise comparison between all the OpAmps used. It was seen that OP27 isn't able to deliver performance as expected because it is getting affected a lot by the noise(1/f noise). OPA140 performs better than all the others.
Attachment 7: Zip file to re-create all data