The circuit shown is from the 1994 Linear Applications Handbook by National Semiconductor. Some of the components are not currently common and should be looked for equivalents.
This circuit can be used to control loads up to 500 mA from the outputs of microcontrollers such...
This circuit with transistors in parallel was found in a Radio Electronics of August 1952....
This Linear Technology circuit can measure currents from 100 pA to 100 uA. The circuit is from the...