A gate turn off thyristor is a pnpn device. In which it can be turned ON like an ordinary SCR
by a positive gate current. However it can be easily turned off by a negative gate pulse of
appropriate magnitude.
Conventional SCR are turned on by a positive gate signal but once the SCR is turned on gate
loses control over it. So to turn it off we require external commutation circuit. These
commutation circuits are bulky and costly. So due to these drawbacks GTO comes into
existence.
The salient features of GTO are:
1. GTO turned on like conventional SCR and is turned off by a negative gate signal of
sufficient magnitude.
2. It is a non latching device.
3. GTO reduces acoustic and electromagnetic noise.
It has high switching frequency and efficiency.
A gate turn off thyristor can turn on like an ordinary thyristor but it is turn off by negative
gate pulse of appropriate magnitude.
Disadvantage
The negative gate current required to turn off a GTO is quite large that is 20% to 30 % of
anode current
Advantage
It is compact and cost less