Product Overview

A semiconductor device called a silicon-controlled rectifier (SCR) is used to control the direction of current. It has three terminals: the anode (A), cathode (K), and gate. The gate leads form a conductive channel. The current passes through the silicon-controlled rectifier only one way. This makes them an ideal device for power control in AC systems.

The SCR works by controlling the voltage across its anode. Its gate is open-circuited and the anode and cathode terminals are connected to each other. When a negative voltage is applied across the anode, it causes the anode to become reverse biased, while the negative voltage at the cathode causes the device to become forward-biased.

When the voltage applied across the SCR exceeds the breakdown voltage, the minority carriers gain energy and collide with other atoms. This produces millions of charge carriers. When the junction J2 is broken, current starts flowing through the SCR. Once the gate is closed, the current can continue to flow and the SCR is turned on. But before this, it must be noted that there is a depletion region around the junction J2.

In addition to the p-type semiconductor, a silicon-controlled rectifier is made up of four layers of semiconductor materials. These layers are connected to each other in a NPNP structure. A transistor in a NPNP circuit has three P-N junctions. A gate is a semiconductor that controls the flow of current between the anode and the cathode.