Friday 27 November 2015

What Are Diodes, GTO And Transistors?


Diodes: It is a semiconductor device with two terminals that allows flow of current in one direction. It has low resistance to current in one direction and a very high resistance on the other. It is a vacuum tube that has two electrodes – a plate (anode) and a heated cathode.
vacuum tube diode

A semiconductor diode was the first semiconductor electronic devices. Most diodes are made of silicon, while selenium or germanium is also used sometimes. Because a diode allows electric current to pass one way but not the other, it is used as a rectifier to convert AC to DC current.

Diodes are also used as signal limiters, voltage regulators, switches, signal modulators, signal mixers etc.

GTO thyristorGTO: Gate Turn-Off Thyristor, is a high powered semi-conductor device. It differs from a normal Thyristor. Unlike them a GTO has a fully controllable switch that can be tuned off and on by a third lead i.e. the Gate lead.

A normal thyristor does not have a fully controllable switch i.e., which can be turned on and off at will. Once it has been turned on or fired, it remains turned on till a turn off state occurs. Which could be anything like a reverse voltage or if the current flowing falls below a certain threshold value.

A GTO can be turned on by a gate signal and can be turned off by one which has negative polarity.

transistor
Transistors: This is semi-conductor device that is used for amplifying and switching electronic signals and power. A transistor has 3 terminals. When voltage or current is applied to one pair of terminal it changes through the other pair. The output power could be higher than the input, a transistor can amplify signals. Most of the transistors are found in integrated circuits.

The three leads that the transistor has are – Base, collector and Emitter. One of the most used transistors is MOSFET.

MOSFET
MOSFET: It stand for Metal Oxide Semiconductor Field Effect Transistor. This is a type of transistors that is used for amplifying or switching electronic signals. Though a MOSFET is a 4 terminal device – Source, Gate, Drain and Body. But as the Body Terminal and the Source Terminal are often connected to each other internally, therefore only three terminals appear in electrical diagrams. MOSFET is one of the most common transistors in both digital and analog circuits.

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