True or False: The RF impedance level of IMPATT diodes is generally lower than that of Gunn diodes.
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AFalse
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BTrue
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CTrue only above 60 GHz
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DFalse unless series resonated
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ECannot be determined
Answer
Correct Answer: False
Explanation
Introduction / Context:Gunn and IMPATT diodes are common solid-state microwave sources but operate on different physical principles and present different device impedances to resonant circuits or transmission lines.
Given Data / Assumptions:
- Typical Gunn diode impedances are relatively low (a few to a few tens of ohms).
- Typical IMPATT diode impedances are higher (tens to hundreds of ohms), depending on design and frequency.
Concept / Approach:Gunn diodes (transferred electron effect) are commonly matched using low-impedance resonant circuits, while IMPATT diodes (avalanche transit-time) exhibit higher negative resistance magnitude and effective impedance, thus often require different matching networks. Therefore, the statement that IMPATT has “lower” impedance than Gunn is incorrect.
Step-by-Step Solution:
Recall typical ranges: Z_Gunn ≈ few Ω to ~20 Ω; Z_IMPATT ≈ ~20 Ω to a few hundred Ω.Compare: Z_IMPATT > Z_Gunn in most practical designs.Hence the assertion “IMPATT impedance is generally lower than Gunn” is false.Verification / Alternative check:Device application notes and oscillator design examples routinely show low-Q, low-Z resonators for Gunns, whereas IMPATT oscillators use higher-Z matching networks or resonators.
Why Other Options Are Wrong:
“True” variants contradict widely observed device characteristics.“Cannot be determined” ignores broad empirical ranges known to practitioners.Common Pitfalls:
Confusing the higher RF power capability of IMPATT in some bands with lower impedance; these are independent attributes.Final Answer:
False