During forward blocking state, the SCR has

During forward blocking state, the SCR has

Right Answer is:

Low current, large voltage


silicon-controlled rectifier or semiconductor-controlled rectifier is a four-layer solid-state current-controlling unidirectional device (i.e. can conduct current only in one direction).

The silicon control rectifier (SCR) consists of four layers of semiconductors, which form NPNP or PNPN structures, having three P-N junctions labeled J1, J2 and J3, and three terminals.

The SCR has Two state

  1. High current Low Impedance ON state
  2. Low current High Impedance OFF state

Forward Blocking Mode

The SCR is said to be forward-biased when the anode is made positive with respect to the cathode. Due to this forward bias, the junction J1 and J3are forward biased and J2 is reverse biased. Hence the forward voltage is to be held by junction J2. A very small current flows from anode to cathode. This current is called forward leakage current. This current is of the order of a few milliamperes. In the forward blocking mode, the voltage can be increased by VBO. When the forward voltage reaches VBO, the SCR turns on.  During Forward Blocking Mode SCR acts as a Resistor.

Scroll to Top