ABSTRACT
The switched device usually requires a current of several milliamperes, possibly several amperes. The current needed for operating the transistor switch is a lot smaller, often only a few microamperes. This makes it possible to control high-current devices from sensors, logic gates and other circuits with low-current output The main limitation is that only devices working on direct current can be switched, but not devices powered by alternating current These points are illustrated by the examples below.
