In an n-type junction field-effect transistor (JFET), under steady-state operation with the gate-to-channel junction reverse biased, will the device conduct when the drain is held at a positive potential and the source at a negative potential (so that VDS is positive)? Explain the correct operating condition for channel conduction in an n-type JFET.

Introduction / Context:
JFETs are voltage-controlled devices where the gate-to-channel junction is normally reverse biased. Understanding which terminal polarities allow conduction is essential for biasing and small-signal design. This item focuses on the polarity requirements for current to flow in an n-type JFET channel.

Given Data / Assumptions:

• Device is an n-type JFET.
• Gate-to-channel junction is kept reverse biased (VGS ≤ 0 referenced to the source).
• Polarities in question: drain positive, source negative, implying VDS = VD − VS > 0.
• Normal room-temperature operation; no breakdown or forward gate conduction.

Concept / Approach:
In an n-type JFET, the channel is n-type semiconductor. Electrons are the majority carriers. With the gate reverse biased, depletion regions pinch the channel to a degree set by VGS. Drain current ID flows when VDS > 0, pulling electrons from source to drain (conventional current from drain to source). The current magnitude follows ID = f(VGS, VDS), saturating when VDS exceeds a threshold often called VDS(sat) in the JFET context, with control primarily through VGS.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets show characteristic curves ID versus VDS for different VGS ≤ 0; conduction increases with more positive VDS until saturation. This confirms that a positive VDS enables current for an n-channel device.

Why Other Options Are Wrong:

• Drain negative (option b) describes p-channel behavior, not n-channel.
• Positive VGS (option c) forward-biases the gate junction, which is incorrect for JFET operation and risks damage.
• Gate shorted to source (option d) is a possible bias (VGS = 0) but not a necessity for every case; it is not a precondition for conduction.

Common Pitfalls:
Confusing JFET polarity with MOSFET conventions, or assuming VGS must be positive for all field-effect devices. JFET gates are reverse biased; MOSFET gates are insulated and can take positive VGS for n-channel operation.

Final Answer:
Correct — with VDS > 0 and the gate reverse biased, an n-type JFET conducts.