Microwave devices – Match device to application List I (Device) A. PIN diode B. GaAs MOSFET (or MESFET) C. Transferred electron device (TED, e.g., Gunn diode) D. Varactor diode List II (Application) Microwave amplification (low-noise or power gain stage) Low-noise microwave generation (oscillator source) Electronic tuning of a microwave oscillator (voltage-variable capacitance) Light-wave detection (photodiode role) Choose the correct mapping.

Introduction / Context:
This match checks practical roles of common solid-state microwave parts used in front ends, oscillators, and control networks. While some parts can serve multiple roles, there are canonical uses that appear across textbooks and datasheets.

Given Data / Assumptions:

• PIN diode: behaves as a current-controlled resistor/isolator at RF; also a widely used photodiode for light detection.
• GaAs MOSFET/MESFET: popular microwave transistor for low-noise and power amplification.
• Transferred electron device (Gunn): negative differential resistance device used for microwave oscillation.
• Varactor: reverse-biased junction used for voltage-controlled capacitance (electronic tuning).

Concept / Approach:

Map parts to their “most associated” applications: PIN diode → optical detection (when used as photodiode) or RF switching/attenuation; GaAs FET → amplification; Gunn (TED) → microwave generation; varactor → tuning (VCOs, multipliers, filters). Among given choices, this yields a clean one-to-one mapping without contradictions.

Step-by-Step Solution:

Verification / Alternative check:

Standard RF handbooks show GaAs FET LNAs, varactor-tuned VCOs/filters, Gunn oscillators, and PIN photodiodes/switches, confirming the typical associations.

Why Other Options Are Wrong:

Swapping FET with varactor or Gunn contradicts their core device physics. Assigning microwave amplification to a varactor or Gunn conflicts with their usual oscillator/tuning roles.

Common Pitfalls:

Over-generalizing the PIN diode solely as an RF switch and forgetting its photodiode use; conflating “low-noise generation” with “amplification.”

Final Answer:

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