Reverse-conducting thyristor (RCT): how many external leads does the device provide?

Introduction / Context:
A reverse-conducting thyristor (RCT) integrates an anti-parallel diode within the same package as the thyristor. Understanding its terminal count clarifies how it connects in power converters where reverse conduction is needed for commutation or freewheeling paths.

Given Data / Assumptions:

• Device type: reverse-conducting thyristor (thyristor + anti-parallel diode internally).
• Standard thyristor terminals are anode (A), cathode (K), and gate (G).
• The freewheel diode is internally bonded anti-parallel to A–K.

Concept / Approach:

RCTs still require a gate to trigger forward conduction. Therefore, despite including an internal diode, they present the same number of external terminals as a standard SCR: three leads (A, K, G). The internal diode does not create extra external terminals; it shares A and K with the thyristor structure.

Step-by-Step Solution:

Verification / Alternative check:

Manufacturers’ datasheets for RCT devices list three pins. Packages and symbols confirm a gate plus two main terminals.

Why Other Options Are Wrong:

• 2 leads: would correspond to a diode or a two-terminal device; an SCR requires a gate.
• 1 or 4+ leads: not representative of standard RCT packages.

Common Pitfalls:

• Assuming the internal diode needs separate pins.
• Confusing RCTs with two-terminal devices like DIACs.

Final Answer:

3