The thyristor can be turned ON by the application of positive current flowing from gate to cathode without increasing the forward voltage across the device upto forward break over level. With positive gate current,
\(I_A=\frac{\propto_2I_G+I_{CO}}{1-(\propto_1+\propto_2)}\)
With sufficiently large IG, the thyristor can be turned ON for any value of I and hence VAK. This is called gate assisted turn on of a Thyristor. A thyristor is usually turned ON by this usual method only.
