Gate turn-off thyristors (GTOs) are four-layer PNPN devices that act as switches, rectifiers, and voltage regulators. Like other thyristors, GTOs can be turned on by the application of a positive gate signal (g > 0); however, unlike other more conventional devices that can be turned off only at a zero crossing of current, GTOs can be turned off at any time by the application of a gate signal equal to zero. Like silicon controlled rectifiers (SCRs) and silicon controlled switches (SCSs), GTOs have three external terminals: an input control terminal (gate), an output terminal (anode), and a terminal common to both the input and output (cathode). Unlike SCRs and SCSs, however, GTOs can be turned on or off by applying the proper pulse at only one terminal, the cathode. Applying a positive pulse to the cathode turns on the GTO. Conversely, applying a negative pulse to the cathode turns off the GTO.

Performance specifications for gate turn-off thyristors (GTOs) include peak repetitive off-state voltage, peak repetitive reverse voltage, peak cycle surge-on current, maximum root mean square (RMS) current, and holding current. Peak repetitive off-state voltage (VDRM) is the maximum instantaneous value of the off state. It includes all of the repetitive transient voltages and excludes all of the non-transient repetitive voltages. Peak repetitive reverse voltage (VRRM) is the maximum reverse voltage that can be applied continuously to the anode and cathode. Peak cycle surge-on current (ITSM), a non-repetitive amount, is the maximum on-state current of short-time duration that can be applied to gate-turn off thyristors for one full cycle of conduction without performance degradation. Maximum RMS current is a measure of the principal current when a device is in the on state for a specified case temperature. Holding current (IH) is the current required to maintain a steady state condition. Additional performance specifications for gate turn-off thyristors include repetitive peak controllable on-state voltage (VTM), power dissipation (Pd), and operating temperature (TJ). Rising ratio of off voltage (dv/dt) is the minimum value of the rate-of-rise of the principal voltage that causes switching from the off state to the on state.

Gate turn-off thyristors (GTOs) are available in a variety of integrated circuit (IC) packages. Basic types include dual in-line package (DIP), discrete package (DPAK), and small outline package (SOP). DIPs can be made of either ceramic (CDIP) or plastic (PDIP). SOP variants include thin small outline package (TSOP), thin shrink small outline L-leaded package (TSSOP), and thin small outline J-leaded package (TSOJ). DPAK variants include integrated packaging (IPAK) and power packaging (PPAK). D2PAK is large surface mounted package that include a heat sink. I2PAK is a plastic package with three leads. DO-15 and DO-35 are diode outline (DO) packages. TO-3, TO-3P, TO-39, TO-92, TO-202, and TO-220 are transistor outline (TO) packages. Metal electrode leadless face (MELF) component diodes have metallized terminals at each end of a cylindrical body.