Hi all,
I've started playing around with the awesome TIA model (TIA_universalopamp_shotnoise.asc) and have a couple of questions or perhaps statements that I'd like verified so I can understand I'm going the right way about things.
I'm designing a low speed (~kHz) high sensitivity photodiode circuit. Initial testing suggest that the optical signals are very low so I'm going to need a high gain, and want to understand the limiting noise components in the circuit so I can choose the correct photodiode and op amp for my circuit.
From what I understand, the main inputs into the model are:
A) The feedback cap & resistor (C1, R1). Used to adjust such that the noise spectrum is flat around frequency of operation, and the gain is sufficient.
B) The photodiode specs: the shunt resistance (Rsh), the photocurrent itself (I1) and the junction capacitance (Cjo in DP)
C) and obviously the cable capacitance, Ccable and actual op amp model.
A few queries:
1. I'm a little confused about the presence of D2, I2, C2 & V3 and how shot noise can be included in this model.
2. Also, what other parameters can be set that define the photodiode?
3. To work out the dark current contribution to the output voltage of the TIA, can I simply put as I1?
Thanks in advance!
