In field-effect devices, when an applied input voltage modulates the conductive channel’s resistance (and therefore current), what is this phenomenon called?

Introduction / Context:
The defining feature of JFETs and MOSFETs is that an electric field, applied via a control terminal (gate), modulates the charge carriers in a semiconductor channel. This electric-field control changes the channel resistance and current without requiring significant input current at the gate.

Given Data / Assumptions:

• Input signal appears at the gate (JFET or MOSFET).
• The gate modulates channel width/charge density.
• We seek the correct term for this mechanism.

Concept / Approach:
Applying a gate voltage establishes an electric field across the gate dielectric (MOSFET) or depletion region (JFET). This field attracts or repels carriers, changing channel conductivity. The generic name for this control principle is the “field effect,” which gives FETs their name.

Step-by-Step Solution:
Apply a gate voltage relative to source.The resulting electric field alters carrier density in the channel.Channel resistance and drain current change accordingly.Therefore, the action is termed the field effect.

Verification / Alternative check:
Device equations (transfer characteristics ID vs. VGS) directly relate current to gate-controlled fields; empirical datasheets confirm near-zero gate current in MOSFETs, distinguishing field control from current injection control (as in BJTs).

Why Other Options Are Wrong:

• Saturization: Nonstandard term; saturation in FETs refers to the constant-current region, not the control mechanism.
• Polarization: Refers to dielectric dipole alignment; not the channel control principle.
• Cutoff: A region where current is minimal due to strong reverse gate bias; not the general effect.

Common Pitfalls:

• Confusing BJT current-controlled behavior with FET field-controlled behavior.
• Assuming gate current modulation is required; in MOSFETs the gate current is ideally zero.

Final Answer:
field effect