The figure shows how to drive a load up to 300 mA with an LM3900. The transistor can be a BD136. We found this setting in the 1994 National Semiconductor Linear Applications Handbook.
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...