SCR internal connection statement check Consider the construction of a silicon-controlled rectifier (SCR). “In a thyristor the gate lead is connected to the n-layer near the p-layer to which the anode is connected.” Is this statement true or false?

Introduction / Context:
Understanding the internal layer structure of an SCR (PNPN device) is essential for appreciating how gating works and why the device exhibits latching behavior. The gate connection location determines how minority carrier injection assists turn-on.

Given Data / Assumptions:

• Standard SCR layer order from anode to cathode: P1–N1–P2–N2.
• Anode connected to outer P1; cathode connected to outer N2.
• Gate terminal is taken from the inner P2 region (also called p-base) near the cathode junction.

Concept / Approach:

The gate must effectively modulate the junction nearest the cathode (J2) to initiate regenerative action in the two-transistor equivalent. Hence, the gate is bonded to the inner p-base (P2) region, not to an n-layer near the anode. This allows a small gate current to inject carriers that forward-bias the internal transistor pair and trigger conduction.

Step-by-Step Solution:

Verification / Alternative check:

The two-transistor model (PNP–NPN) shows that injecting into the P2 base region facilitates rapid turn-on via positive feedback.

Why Other Options Are Wrong:

Marking the statement as true contradicts SCR construction; there is no standard variant where the gate connects to an n-layer near the anode.

Common Pitfalls:

Confusing the gate-bond region (P2) with the outer P1 anode region or with N-type layers; misreading cross-sectional diagrams.

Final Answer:

False