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 TPA3100D2 integrated circuit from Texas Instruments (www.ti.com) consists of an efficient...
This circuit was found in a 1965 General Electric publication. The circuit can be adapted to...
This circuit, which combines a bipolar with any JFET, was found in the April 1993 issue of...