
Chapter
3
Active components
If passive components are the cogs and pinions of a
circuit, an active component is the mainspring.
The analogy is not quite exact perhaps, for the
mainspring stores and releases the energy to drive
the clockwork, whereas an active component
drives a circuit by controlling the release of energy
from a battery or power supply in a particular
manner. In this sense, active devices have existed
since the days of the first practical applications of
electricity for communications. For although the
receiving apparatus of the earliest electric tele-
graphs may have been passive in the sense that the
indicators were operate ...