About Transistors. Features
About transistors.Features
The transistor is a semiconductor electronic device category that has three terminals (terminals or electrodes), linking the three regions of the crystal semiconductor.Transistor aspect depends on the nature of the application for which they are intended.
Low-power transistors
These transistors are encapsulated in plastic or metal and are not fitted to the radiator.
Power Transistors
These transistors are encapsulated in plastic or metal and are fitted to the radiator.
Low Frequency Transistors
Transistors are designed for use up to a frequency of about 100 kHz, audio circuits and power control.
High frequency transistors
Are transistors for applications at frequencies above 100 kHz, as the radio-TV, microwave circuits, switching circuits etc.
Working principle
In normal operation emitter-base junction is forward biased and collector-base junction is reverse biased.Base-emitter junction, being biased, is traversed by a direct current (diffusion current) IE, high ratio of reverse current (residual) and a wide range of currents, with typical values of 0.6 to 0 , 7, or 0.2 V.
Base-collector junction being reverse biased, is characterized by its current, conversely, very small, nano amp.order for transistors and silicon germanium transistors order to micro amps.Transistor characteristic is electrical coupling of the two junctions.
1.emitter junction is highly asymmetric
2.basis will be very thin, so that the flow of majority carriers from emitter to reach virtually all of the collector region crossing
Construction:
The transistors are made on a semiconductor substrate (usually silicon, germanium less, but not only).The technology of processing varies depending on the desired transistor.For example, a PNP type transistor is performed on a P-type substrate, which is created by various methods (diffusion, for example) an N-type area, which will form the base of the transistor.
Use:
Transistors can be used in electronic equipment with discrete components in the signal amplifiers (in audio, video, radio), instrumentation amplifiers, oscillators, modulators and demodulators, filters, power supplies or switching or linear integrated circuit technology today, allowing integration in a single capsule of millions of transistors.