Explain construction detail of a thyristor
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The silicon controlled rectifier ( SCR ) is a three terminal semiconductor switching device which can be used as a controlled switch to perform various functions such as rectification, inversion and regulation of power flow.
An SCR can handle currents upto several thousand amperes and voltages upto more than 1kV.
The SCR has appeared in the market under different names such as thyristor, thyrode transistor.
Like the diode, SCR is a unidirectional device,i.e. it will only conduct current in one direction only, but unlike a diode, the SCR can be made to operate as either an open-circuit switch or as a rectifying diode depending upon how its gate is triggered.
In other words, SCR can operate only in the switching mode and cannot be used for amplification.
Hence, it is extensively used in switching d.c. and a.c., rectifying a.c. to give controlled output, converting d.c. into a.c. etc.
Constuctional Details of SCR
When a pn junction is added to a junction transistor, the resulting three pn junctions device is called a silicon controlled rectifier.
It is clear that it is essentially an ordinary rectifier (pn) and a junction transistor (npn) combined in one unit to form pnpn device.
Three terminals are taken; one from the outer p-type material called anode A, second from the outer layer of n-type material called cathode K and the third from the base of transistor section and is called gate G.
In the normal operating conditions of SCR, anode is held at high positive potential w.r.t. cathode and gate at small positive potential w.r.t. cathode.
An SCR can handle currents upto several thousand amperes and voltages upto more than 1kV.
The SCR has appeared in the market under different names such as thyristor, thyrode transistor.
Like the diode, SCR is a unidirectional device,i.e. it will only conduct current in one direction only, but unlike a diode, the SCR can be made to operate as either an open-circuit switch or as a rectifying diode depending upon how its gate is triggered.
In other words, SCR can operate only in the switching mode and cannot be used for amplification.
Hence, it is extensively used in switching d.c. and a.c., rectifying a.c. to give controlled output, converting d.c. into a.c. etc.
Constuctional Details of SCR
When a pn junction is added to a junction transistor, the resulting three pn junctions device is called a silicon controlled rectifier.
It is clear that it is essentially an ordinary rectifier (pn) and a junction transistor (npn) combined in one unit to form pnpn device.
Three terminals are taken; one from the outer p-type material called anode A, second from the outer layer of n-type material called cathode K and the third from the base of transistor section and is called gate G.
In the normal operating conditions of SCR, anode is held at high positive potential w.r.t. cathode and gate at small positive potential w.r.t. cathode.
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