JFET terminology — are pinch-off voltage and breakdown voltage the same? Consider a JFET: the gate-source pinch-off voltage (|V_P|) defines channel control, while breakdown (e.g., gate-to-channel avalanche) defines destructive or limiting conditions. Evaluate the statement that these two are “the same voltage level.”

Difficulty: Easy

Correct Answer: Incorrect

Explanation:


Introduction / Context:
Properly biasing a JFET requires distinguishing between the pinch-off voltage, which is a normal operating parameter, and breakdown voltages, which are stress or limit ratings. Confusing them can lead to device damage or misinterpretation of I–V curves.



Given Data / Assumptions:

  • Pinch-off voltage V_P (often specified as V_GS(off)) is the gate-source voltage at which the channel current is reduced to a small value (near cutoff).
  • Breakdown voltages (e.g., BV_GD, BV_GS, BV_DS) indicate avalanche or tunneling onset; exceeding them risks permanent damage.


Concept / Approach:
V_P defines the control range of the JFET channel and is typically a few volts (negative for n-channel devices). Breakdown voltages are usually larger in magnitude and mark the onset of high, potentially destructive currents. They serve entirely different purposes: one is an operating parameter, the other a limit rating.



Step-by-Step Solution:

Identify V_P (or V_GS(off)) from the transfer curve: current approaches zero as V_GS → V_P.Identify breakdown on I–V curves: sharp current increase at a high reverse bias.Compare magnitudes and roles: they do not coincide; breakdown exceeds normal control range.Conclusion: calling them the same voltage is incorrect.


Verification / Alternative check:
Datasheets list V_GS(off) separately from breakdown ratings (BV_GS, BV_GD, BV_DS), confirming distinct definitions and values.



Why Other Options Are Wrong:

Correct / conditional qualifiers: contradict standard datasheet terminology and device physics.


Common Pitfalls:
Misreading the term “pinch-off” used for channel current saturation in FETs versus catastrophic junction breakdown events.



Final Answer:
Incorrect

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