This Linear Technology circuit can measure currents from 100 pA to 100 uA. The circuit is from the 80's, using a component of the era. Transistors are general purpose types.
This circuit is from a 1968 Electronic Design. The characteristics of the output transformer are not...
We found this circuit in the July 1988 Radio Electronics magazine. The frequencies are given by...
This circuit is from 1967 General Electric documentation. It uses SUS which are not very common...