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Difficulty: MediumTransistors

While standard bipolar junction transistors (BJTs) operate as current-controlled components, field-effect transistors (FETs) are commonly used in high-impedance input stages. What is the primary operating mechanism of a field-effect transistor?

  1. A
    Controlling collector current by drawing a continuous input current through a forward-biased base junction
  2. Regulating current between the source and drain using an electric field established by a gate voltageAnswer
  3. C
    Directing electron flow by altering magnetic flux across a series of reverse-biased diode barriers
  4. D
    Modulating channel resistance by requiring a high input control current at the gate terminal

Answer

Regulating current between the source and drain using an electric field established by a gate voltage
A field-effect transistor (FET) controls the flow of electrical charge carriers between the source and drain terminals by varying the strength of an electrostatic field within the semiconductor channel. This field is established by applying a voltage to the gate terminal, allowing the device to modulate conductivity with almost zero input gate current.

Step-by-Step Solution

1
Identify the fundamental category and terminals of a Field-Effect Transistor (FET)
FETs have three primary terminals: Gate, Drain, and Source.
Recognizing terminal designations separates FET functionality from BJT terminals (Base, Collector, Emitter).
2
Determine the control mechanism of a FET
An electric field created by voltage applied to the gate controls the conductive channel between the source and drain.
FETs are voltage-controlled solid-state devices that draw negligible gate current due to extremely high input resistance.

Key Concept

Field-Effect Transistor (FET) Voltage-Controlled Operation
Estimated Time:1m 0s
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Topics

Transistors

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