The ability of a transistor to control a large Emitter - Collector current by means of a small
Base - Emitter current means it can act as a switch or amplifier: as a switch by turning the
Base - Emitter current on and off, or as an amplifier by superimposing a small alternating
current signal on the Bias voltage. In conjunction with the Junction Diode and other electronic
components, such as resistors, capacitors and inductors, the applications for the transistor are
almost limitless.
Furthermore, the ability to control precisely those areas to which doping is applied, using
photo-etching techniques, means that all of the above components can be incorporated into
a highly sophisticated and complex circuit within a single, small piece of silicon. The ubiquitous
computer chip is one such example.
For the future, as production techniques improve, faster, more powerful circuits will be
contained in ever smaller packages, leading in turn to more sophisticated technology being
incorporated in the modern airliner