In an n-channel JFET, what is the doping type of the gate region that controls channel conduction?
Electronics and Communication Engineering
Electronic Devices and Circuits
Difficulty: Easy
Choose an option
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An type
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Bp type
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Ceither n or p
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Dpartially n and partially p
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Eintrinsic (undoped)
Answer
Correct Answer: p type
Explanation
Introduction / Context:JFETs (junction field-effect transistors) operate by reverse-biasing a p–n junction between the gate and the channel. Recognizing which region is doped as p or n helps understand pinch-off, VGS control, and device fabrication.
Given Data / Assumptions:
- Device type: n-channel JFET.
- Channel: n-type semiconductor providing electron conduction.
- Gate: forms a p–n junction with the channel.
Concept / Approach:To form a controllable depletion region around the channel, the gate must be p-type. Applying reverse bias between gate and channel widens the depletion region, reducing channel width until cutoff (pinch-off) occurs.
Step-by-Step Solution:
n-channel → conduction by electrons in n-type channel.Gate region must be opposite type, i.e., p-type, to form the p–n junction.Therefore, correct answer: p type.Verification / Alternative check:
Compare with p-channel JFET: channel is p-type, gate is n-type, confirming the symmetry.Why Other Options Are Wrong:
n type: would create an ohmic contact, not a junction.Either or partial doping: meaningless for junction formation.Intrinsic: not practical in real devices.Common Pitfalls:
Confusing channel doping with gate doping; gate is always opposite type.Final Answer:
p type