Draw labeled constructional diagram for GTO and describe its working principle with V-I characteristics.

Ans:

Constructional diagram: 

Operating Principle:- 

 Basic operation of GTO is same as that of the conventional SCR but the major difference between is that the conducting GTO can be turned off by applying a negative gate current to it. Thus positive gate current turns it on and negative gate current turns it off. 

•  From two transistor model of GTO both transistor Q1 and Q2 are in saturation when the GTO is in it’s on state. 

• If the base current of Q2 could be made less than the value needed for maintaining it in saturation, then Q2 will come out of saturation and will be in active state, this will reduce the regeneration and GTO will begin to turn off.  

•  In order to reduce the base current of Q2 & –ve gate current must flow in the direction as shown in diagram A. It can be proved that the negative gate current required for turning off a conducting GTO. 

V-I characteristics: