Ans: Symbol and V-I characteristics of GTO:
Operation of GTO: i) As the applied anode to cathode voltage is increased above zero, very small current (leakage current) flows through the device. Under this condition the GTO is said to be off. It will be continued till the applied voltage reaches the forward Breakover voltage (VBRF). ii) If the anode-cathode (applied) voltage exceeds the breakover voltage, the device conducts heavily and the GTO is turned ON. The anode to cathode voltage decreases quickly because, the GTO offers very low resistance when it is ON, hence it drops very low voltage across it. iii) At this stage the GTO allows more current to flow through it. The amplitude of the current is depending upon the supply voltage and load resistance connected in the circuit. iv) If the value of the gate current Ig is increased above zero, the GTO turns ON even at lower anode-cathode voltage (less than forward breakover voltage, VBRF). v) If the polarity of applied voltage is reversed, we get the reverse characteristics. vi) In reverse direction GTO breaks down at very low voltage (VBRR). The reverse breakdown voltage is of the order of 20 to 30 volt only.