Device characteristics – Match characteristic to the appropriate device List I (Characteristic) A. Voltage-controlled device B. Current-controlled device C. Conductivity modulation device D. Negative-conductance device List II (Device) BJT UJT FET IMPATT diode Choose the correct mapping.

Introduction / Context:
Different semiconductor devices are categorized by how their control input affects conduction and by special effects like negative conductance or conductivity modulation. Matching these attributes helps in quickly identifying suitable parts for amplification, switching, oscillation, or triggering.

Given Data / Assumptions:

• FETs are voltage-controlled (gate modulates channel with negligible input current).
• BJTs are current-controlled (collector current depends on base current).
• UJT exhibits conductivity modulation in its emitter-triggered behavior and negative-resistance region often used for relaxation oscillators.
• IMPATT diodes are classic negative-conductance microwave diodes due to impact ionization and transit-time effects.

Concept / Approach:

Assign each characteristic to the best-known exemplar: voltage control → FET; current control → BJT; conductivity modulation → UJT (emitter injection alters channel conductivity); negative conductance → IMPATT (microwave oscillators/amplifiers in the negative-resistance region).

Step-by-Step Solution:

Verification / Alternative check:

Datasheets and textbooks consistently describe FET gate control as voltage-driven, BJTs as current-driven, UJTs as conductivity-modulated triggers, and IMPATTs as negative-resistance microwave devices.

Why Other Options Are Wrong:

Swapping BJT and FET reverses fundamental control laws; attributing negative conductance to BJT or UJT confuses low-frequency negative resistance with the high-frequency negative conductance of IMPATT.

Common Pitfalls:

Assuming every device with a negative-resistance region is a “negative-conductance” microwave device; conflating MOSFET gate leakage with current control.

Final Answer:

A-3, B-1, C-2, D-4.