This circuit has a sensitivity of 2uW. We found it in documentation from the 1980s. The integrated circuit is from that time. Equivalents can be tried.
This circuit was found in the National component manual which is not currently simple to obtain....
In this circuit, the current capacity doubles, but is still of the order of microamps. The...
We found this circuit in a Hands On Electronics from the 90s. However, the circuit can still be...