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.
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AA-1, B-2, C-4, D-3
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BA-4, B-1, C-2, D-3
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CA-2, B-3, C-1, D-4
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DA-3, B-4, C-2, D-1
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EA-4, B-3, C-1, D-2
Answer
Correct Answer: A-4, B-1, C-2, D-3
Explanation
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:
A (PIN diode) → 4 (light-wave detection).B (GaAs FET) → 1 (microwave amplification).C (TED/Gunn) → 2 (microwave generation; “low-noise” is relative here compared with some tubes).D (Varactor) → 3 (electronic tuning of MW oscillator).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.