Thyristor

The name thyristor  is derived bya  combination of the  capital  letters from  thyratron and  translstor. This means that thyristor is a solid  state device like  a transistor  and has characteristics similar  to that of  a thyratron  tube. Basically  thyistor is a family  of power semiconductor device and SCR is an oldest  member of this family  that why  some  times we use the  name  thyristor  instead of SCR.

SCR  stand  for silicon controlled rectifier. It is four layer  PNPN three  junctions ( J1,J2, and J3) and three terminal device. The  terminals are  named as anode A  cathode K and  gate G as shown in figure.

                                           Figure  Thyristor  basic  structure  symbol

The terminal  anode  is connected to outer region the terminal cathode  is connected to  outer  in region  and the terminal gate is connected to inner P region, when a small  current  flows  into the  gate  this allows  a larger current  to flow  from the  anode  to the cathode. Even  when the current  into the gate shop  the thyristor continues to allow current  to flow  from  anode  to cathode. It  latches on. Thyristors  are usually manufactured from silicon because of its overall properties. It also has  goo  thermal  properties. The  other reason for using  silicon  is that  silicon technology is well  established. As a  result  it is very cheap  and easy for semiconductor  manufacturers  to uses.