Paul,
You probably want to build the input stage discretely if you want higher transimpedance gain. Instrumentation amplifiers normally have relatively low feedback resistors to minimize thermal noise for the typical voltage amplifier use case. You could…
Part Number: OPA188 Other Parts Discussed in Thread: OPA197 , OPA333 , OPA2387 , OPA2197 , OPA2192 , OPA2391 , OPA2392 , OPA2191 the following curcuit is a constane current circuit. and the output current range is 200nA to 4uA. we found that the circuit will…