Which semiconductor is used for AC outputs in solid state switching?

Which semiconductor is used for AC outputs in solid state switching?

• A. Diode
• B. Thyristor
• C. Transistor
• D. Triac

Answer: (D)

For AC switching, you need a device that can turn on and conduct current in both directions of the AC waveform. The triac does this naturally: it’s a bidirectional thyristor, so a gate pulse can trigger conduction in either direction, and it stays on until the current drops to zero at the end of each half-cycle. That makes it ideal for controlling AC power with a single component, like in light dimmers or motor speed controllers. Diodes only conduct in one direction, so they can’t handle full AC flow by themselves. A thyristor (SCR) also conducts in only one direction, so you’d need two back-to-back to handle AC, which adds complexity. Transistors can switch AC, but require additional circuitry to block current in both directions. The triac provides simple, effective bidirectional switching for AC power, which is why it’s used for AC outputs in solid-state switching.

For AC switching, you need a device that can turn on and conduct current in both directions of the AC waveform. The triac does this naturally: it’s a bidirectional thyristor, so a gate pulse can trigger conduction in either direction, and it stays on until the current drops to zero at the end of each half-cycle. That makes it ideal for controlling AC power with a single component, like in light dimmers or motor speed controllers.

Diodes only conduct in one direction, so they can’t handle full AC flow by themselves. A thyristor (SCR) also conducts in only one direction, so you’d need two back-to-back to handle AC, which adds complexity. Transistors can switch AC, but require additional circuitry to block current in both directions. The triac provides simple, effective bidirectional switching for AC power, which is why it’s used for AC outputs in solid-state switching.