NPN Transistor—Three-element semiconductor formed by placing a lightly doped, very thin region of P-type silicon or germanium between two regions of N-type material

NPN Transistor—Three-element semiconductor formed by placing a lightly doped, very thin region of P-type silicon or germanium between two regions of N-type material

• A. Junction Diode
• B. Bipolar Transistors
• C. Field Effect Transistor
• D. Insulated Gate Bipolar Transistor

Answer: (B)

The idea being tested is how a transistor is built from three regions and two PN junctions. The description specifies a lightly doped, very thin P-type region between two N-type regions, which is the classic structure of a Bipolar Junction Transistor in the NPN form. Here, the three regions are emitter (N), base (P), and collector (N). The thin base allows carriers to move from the emitter into the base and then on to the collector, enabling current amplification when the device is properly biased (forward-active: emitter-base forward biased, base-collector reverse biased). This is why the best label is Bipolar Transistors. It’s not a junction diode, which is two-terminal and lacks the three-region structure needed for amplification. It’s not a Field Effect Transistor, which controls current with an electric field in a channel rather than through PN junctions. And it’s not an insulated-gate device, which refers to a more complex class of devices that use a gate oxide-insulated control but aren’t described by this simple three-region PN structure.

The idea being tested is how a transistor is built from three regions and two PN junctions. The description specifies a lightly doped, very thin P-type region between two N-type regions, which is the classic structure of a Bipolar Junction Transistor in the NPN form. Here, the three regions are emitter (N), base (P), and collector (N). The thin base allows carriers to move from the emitter into the base and then on to the collector, enabling current amplification when the device is properly biased (forward-active: emitter-base forward biased, base-collector reverse biased).

This is why the best label is Bipolar Transistors. It’s not a junction diode, which is two-terminal and lacks the three-region structure needed for amplification. It’s not a Field Effect Transistor, which controls current with an electric field in a channel rather than through PN junctions. And it’s not an insulated-gate device, which refers to a more complex class of devices that use a gate oxide-insulated control but aren’t described by this simple three-region PN structure.