Hello all, I am interested in measuring the photoresponse of a transistor with a fixed source-drain bias. I would like to feed the drain current into a current preamplifier and output the preamplifier signal to another location. The preamplifier has a very low current maximum, so I will use a current divider. The preamplifier has a known input resistance. I am using an SMU to provide a constant VSD, and it is important to be able to fix this potential at whatever value I want. I have attached what I can come up with, but I am not sure this is the best approach.... In the cartoon below, I draw a cartoon and a (at least I think so) equivalent circuit. I have modeled the SMU potential across the SD as a battery with resistor in series. The CPA (Current preamplifier) is also modeled as a resistor. I believe the input has to be in series with I1 (current measurement). I have also included equations for what I think will be I1 and I0. Any advice for whether this looks reasonable, or improvements would be greatly appreciated!!!! Thanks.