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.
The range of generated signals depends on coil L1. The circuit was found in old English...
This circuit was suggested by Electronic Engineering in a 1980s publication. The circuit makes use...
This automotive tachometer circuit uses a FET and a 1 mA full-scale instrument. We found it in the...