DC Biasing for JFET and MOSFET
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Questions and Answers

What is a key characteristic of an Enhancement MOSFET (E-MOSFET) in terms of its operation mode?

  • Has an IDSS parameter
  • Has no structural channel (correct)
  • Can only operate in depletion mode
  • Operates in both enhancement and depletion modes
  • What happens when the gate voltage is below the threshold in an n-channel Enhancement MOSFET?

  • The IDSS parameter affects the operation
  • It operates in depletion mode
  • A channel is formed with increased conductivity
  • No channel is formed (correct)
  • How does the conductivity of the channel in an Enhancement MOSFET change with an increase in gate-source voltage?

  • Remains constant
  • Increases (correct)
  • Decreases
  • Is not affected
  • Which statement is true about the gate voltage required for an n-channel E-MOSFET and a p-channel E-MOSFET to operate?

    <p>n-channel requires a positive VGS while p-channel requires a negative VGS</p> Signup and view all the answers

    Which configuration describes an Enhancement MOSFET used as a switch?

    <p>Normally off configuration</p> Signup and view all the answers

    Which technologies are EMOSFET technologies developed for higher power dissipation?

    <p>LD MOSFET, VMOSFET, TMOSFET</p> Signup and view all the answers

    In which region of transistor action are both junctions forward biased?

    <p>Saturation region</p> Signup and view all the answers

    What is the term used to describe the operating point of a transistor with time-varying sources out of the circuit?

    <p>Q-point</p> Signup and view all the answers

    Which region of transistor action involves the base-emitter junction being forward biased and the collector-base junction being reverse biased?

    <p>Active region</p> Signup and view all the answers

    What is the straight line drawn on the collector curves between the cut-off and saturation points of a transistor called?

    <p>Loadline</p> Signup and view all the answers

    Which H-parameter represents the short circuit forward current gain of a Bipolar Junction Transistor (BJT)?

    <p>hf</p> Signup and view all the answers

    What happens to a transistor in the cut-off region?

    <p>Both junctions are reverse biased.</p> Signup and view all the answers

    Which term is sometimes used to refer to MOSFETs due to the presence of an insulated gate?

    <p>IGFETs</p> Signup and view all the answers

    How does a Depletion MOSFET differ from JFET?

    <p>It has no PN junction structure.</p> Signup and view all the answers

    What is the primary difference between Depletion MOSFET and Enhancement MOSFET?

    <p>Operation modes - depletion and enhancement</p> Signup and view all the answers

    In which mode is the Depletion MOSFET normally operated?

    <p>Depletion mode</p> Signup and view all the answers

    What happens when a positive gate voltage is applied to an Enhancement Mode MOSFET?

    <p>More conduction electrons are attracted to the channel.</p> Signup and view all the answers

    What configuration is a normally-on switch when using a D-MOSFET?

    <p>Depletion mode</p> Signup and view all the answers

    Study Notes

    Enhancement MOSFET (E-MOSFET)

    • Operates only in enhancement mode, with no depletion mode. • No structural channel and no IDSS parameter. • An n-channel E-MOSFET requires a positive gate voltage above threshold to induce a channel. • A layer of negative charges (inversion layer) is created in the substrate portion adjacent to the SiO2 layer. • A p-channel E-MOSFET requires a negative VGS.

    E-MOSFET Characteristics

    • Conductivity of the channel is enhanced by increasing the gate-to-source voltage. • No channel is formed for gate voltage below the threshold. • Configured as a switch, the device is normally off.

    E-MOSFET Technologies

    • LD MOSFET, VMOSFET, and TMOSFET are E-MOSFET technologies for higher power dissipation.

    Amplifiers

    Classification of Amplifiers

    • Voltage Amplifier: voltage controlled source, e.g., Op-amps. • Current Amplifier: current controlled source, e.g., BJTs.

    BJT Transistor Biasing

    Regions of Transistor Action

    • Active region: base-emitter junction is forward biased, collector-base junction is reverse biased. • Saturation region: both junctions are forward biased. • Cut-off region: both junctions are reverse biased.

    Loadline and Q-Point

    • Loadline: a straight line drawn on the collector curves between the cut-off and saturation points. • Q-point (Quiescent point): the operating point of the transistor with time-varying sources removed.

    BJT Small Signal Analysis

    Transistor Hybrid Equivalent Circuit

    • hi: short circuit input impedance. • hr: open circuit reverse voltage gain (voltage feedback ratio). • hf: short circuit forward current gain.

    Field Effect Transistors (FETs)

    MOSFET

    • A type of FET with an insulated gate, sometimes called IGFET. • Two basic types: Depletion MOSFET (D-MOSFET) and Enhancement MOSFET (E-MOSFET).

    Depletion MOSFET (D-MOSFET)

    • Drain and source are diffused into substrate material, connected by a narrow channel adjacent to the insulated gate. • Operated in depletion mode or enhancement mode. • Normally operated in depletion mode, and configured as a switch, it is normally-on.

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    Description

    Test your knowledge on DC biasing techniques used for Junction Field Effect Transistors (JFET) and Metal Oxide Semiconductor Field Effect Transistors (MOSFET). Understand how to set up proper biasing for optimal transistor operation.

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