Silicon Controlled Rectifier Actual. A silicon controlled rectifier is made up of 4 semiconductor layers of alternating p and n type materials which forms npnp or pnpn structures. It has three p n junctions namely j 1 j 2 j 3 with three terminals attached to the semiconductors materials namely anode a cathode k and gate g.
Silicon controlled rectifier consists of three terminals anode cathode and gate unlike the two terminal diode anode and cathode rectifier. This extra terminal is called the gate and it is used to trigger the device into conduction latch it by the application of a small voltage. A silicon controlled rectifier or scr is essentially a shockley diode with an extra terminal added.
The principle of four layer p n p n switching was developed by moll tanenbaum goldey and holonyak of bell laboratories in 1956.
These scrs will be widely used in electronic devices which have to control high voltage and power. The anode and cathode of an scr are similar to the anode and cathode of an ordinary diode. It can also be applicable in medium and high ac power operations like motor control function. A silicon controlled rectifier scr is a four layer pnpn semiconductor device that uses three electrodes for normal operation.
