Which transistor type is formed by placing a lightly doped P-type region between two N-type regions?

Which transistor type is formed by placing a lightly doped P-type region between two N-type regions?

• A. NPN Transistor
• B. PNP Transistor
• C. Junction Field-Effect Transistor
• D. Darlington Pair

Answer: (A)

A lightly doped P-type region between two N-type regions forms an NPN transistor. In this structure, the outer N regions act as the emitter and collector, while the thin, lightly doped P-type middle region serves as the base. When the emitter-base junction is forward biased and the base-collector junction is reverse biased, electrons are injected from the emitter into the base and quickly swept into the collector. The base’s light doping and thinness minimize recombination, so most electrons reach the collector, producing current gain. The other options don’t fit this arrangement: a PNP transistor would have a P-type emitter and collector with an N-type base (P-N-P); a junction field-effect transistor operates by controlling a channel with an electric field rather than a PN junction-based emitter-base structure; a Darlington Pair consists of two transistors in a specific configuration to boost gain, not a single PN stack.

A lightly doped P-type region between two N-type regions forms an NPN transistor. In this structure, the outer N regions act as the emitter and collector, while the thin, lightly doped P-type middle region serves as the base. When the emitter-base junction is forward biased and the base-collector junction is reverse biased, electrons are injected from the emitter into the base and quickly swept into the collector. The base’s light doping and thinness minimize recombination, so most electrons reach the collector, producing current gain.

The other options don’t fit this arrangement: a PNP transistor would have a P-type emitter and collector with an N-type base (P-N-P); a junction field-effect transistor operates by controlling a channel with an electric field rather than a PN junction-based emitter-base structure; a Darlington Pair consists of two transistors in a specific configuration to boost gain, not a single PN stack.