Transistors
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Questions and Answers

Which type of transistor configuration is most commonly used?

  • Unipolar Junction Transistor
  • pnp Transistor
  • Field Effect Transistor
  • npn Transistor (correct)

In a bipolar junction transistor, which junction is forward biased?

  • Emitter-Collector Junction
  • Emitter-Base Junction
  • Base-Collector Junction
  • Base-Emitter Junction (correct)

What is the primary function of the base in an npn transistor?

  • To provide a path for electron flow
  • To dissipate excess heat
  • To collect the majority of current
  • To control current flow between collector and emitter (correct)

What analogy is used to explain the operation of a bipolar junction transistor?

<p>Fluid Flow (A)</p> Signup and view all the answers

In a pnp transistor, the base must be connected to which potential to allow current flow?

<p>Low potential (C)</p> Signup and view all the answers

Which statement accurately describes the collector in an npn transistor?

<p>It has a higher potential than the emitter. (B)</p> Signup and view all the answers

What occurs when a signal is applied as a current to the base of a BJT?

<p>A valve between the collector and emitter opens and closes. (A)</p> Signup and view all the answers

How is the flow of electricity considered in a BJT?

<p>Flow is considered positive to negative. (A)</p> Signup and view all the answers

What significant problem did transistors solve compared to vacuum tubes?

<p>Reduced size and power consumption (C)</p> Signup and view all the answers

Who were the creators of the first transistors?

<p>William Shockley, John Bardeen, and Walter Brattain (D)</p> Signup and view all the answers

What is the role of dopants in semiconductor materials?

<p>To enhance electrical properties (A)</p> Signup and view all the answers

Which of the following is a P-type dopant?

<p>Boron (D)</p> Signup and view all the answers

Under forward bias conditions in a diode, where does current flow?

<p>From P to N (D)</p> Signup and view all the answers

In N-type semiconductors, which element commonly acts as a dopant?

<p>Phosphorus (B)</p> Signup and view all the answers

Which of the following describes the term 'transistor'?

<p>A combination of transconductance and variable resistor (A)</p> Signup and view all the answers

What happens to dopants in a semiconductor device over time?

<p>They migrate due to excessive heat (A)</p> Signup and view all the answers

What is the minimum number of transistors that can be found in an advanced microprocessor today?

<p>1.7 billion (B)</p> Signup and view all the answers

What occurs during reverse bias in a diode?

<p>Current is blocked (D)</p> Signup and view all the answers

What occurs when the gate voltage of a MOSFET is increased past the threshold voltage?

<p>Electrons from the source and drain form an inversion layer. (B)</p> Signup and view all the answers

What is the channel length in a MOSFET?

<p>The distance between source and drain. (A)</p> Signup and view all the answers

During which state does a MOSFET not conduct current?

<p>When the gate voltage is zero. (D)</p> Signup and view all the answers

What happens to the depletion region when the gate voltage is increased?

<p>The depletion region expands until it covers the entire channel. (D)</p> Signup and view all the answers

What must be present for a MOSFET to operate in the linear (or triode) region?

<p>An applied voltage across the source and drain. (A)</p> Signup and view all the answers

What is the primary difference between FETs and BJTs in terms of their operation?

<p>FETs switch by voltage, BJTs by current. (A)</p> Signup and view all the answers

Which type of transistor is designed to allow for much greater gain in a circuit?

<p>Darlington Transistor. (B)</p> Signup and view all the answers

In a P-N junction, what naturally occurs when no electric fields are present?

<p>A depletion region is created. (A)</p> Signup and view all the answers

What are the primary components of a MOSFET transistor?

<p>Gate, Drain, Source. (A)</p> Signup and view all the answers

Which FET type is most commonly used in practice?

<p>Metal-Oxide-Semiconductor FET. (A)</p> Signup and view all the answers

What additional lead is present in BJTs that is not applicable to FETs?

<p>Collector. (A)</p> Signup and view all the answers

How do the gate leads of MOSFETs and JFETs function in digital circuits?

<p>They act as voltage switches. (D)</p> Signup and view all the answers

What is the role of the body lead in a FET transistor?

<p>It is not applicable to all FETs. (B)</p> Signup and view all the answers

What property defines the operation principles of a bipolar junction transistor?

<p>Current amplification. (A)</p> Signup and view all the answers

When comparing FETs to BJTs, which statement is correct?

<p>FETs are easier to integrate into circuits. (A)</p> Signup and view all the answers

Which terminal of a Bipolar Junction Transistor (BJT) is responsible for controlling the output current?

<p>Base (C)</p> Signup and view all the answers

What distinguishes a Field Effect Transistor (FET) from a Bipolar Junction Transistor (BJT)?

<p>FET operates with conduction involving either holes or electrons. (A)</p> Signup and view all the answers

In an NPN BJT, what is the current flow direction when it is in the active region?

<p>From Emitter to Collector. (C)</p> Signup and view all the answers

Which of the following is true concerning the input resistance of FETs?

<p>FETs have very high input resistance, allowing negligible current flow. (D)</p> Signup and view all the answers

What defines an enhancement-mode FET compared to a depletion-mode FET?

<p>Enhancement-mode FET requires a voltage to turn ON. (D)</p> Signup and view all the answers

What are the main terminals of a Field Effect Transistor (FET)?

<p>Source, Drain, Gate (C)</p> Signup and view all the answers

In which scenario would you use a power transistor?

<p>To handle high current and voltage applications. (D)</p> Signup and view all the answers

What is the primary application of transistors in electronic circuits?

<p>For switching, amplification, and as variable resistors. (D)</p> Signup and view all the answers

How do BJTs operate concerning the current flowing through their terminals?

<p>The Base controls the current into the Emitter and Collector. (B)</p> Signup and view all the answers

Which of the following statements about the operation of an N-channel FET is true?

<p>The channel is typically made from N-type material. (A)</p> Signup and view all the answers

Flashcards

NPN Transistor

A type of bipolar junction transistor where the base is a thin region with less dopants.

BJT (Bipolar Junction Transistor)

A three-terminal electronic component used for amplifying or switching electronic signals and power.

Base, Collector, Emitter

The three terminals of a BJT. Base is thin region with less dopants; the collector reverses biased; and emitter forward biased.

Base-Emitter Junction (Forward Biased)

The junction between the base and emitter is forward biased, allowing current flow.

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Base-Collector Junction (Reverse Biased)

The junction between the base and collector is reverse-biased, preventing current flow to the collector when the base is low.

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NPN Transistor Operation

Current flows from collector to emitter when a high potential is applied to the base.

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PNP Transistor Operation

Current flows from emitter to collector when a low potential is applied to the base.

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BJT Signal Amplifier

A small signal applied to the base controls a much larger current flow between the collector and emitter.

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Transistor as signal amplifier

Transistors amplify input signals, producing outputs of the same shape but larger amplitude.

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Darlington Transistor

A type of transistor configuration that provides higher gain in circuits.

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Field Effect Transistor (FET)

A transistor that switches based on voltage, not current.

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MOSFET

A type of FET using a metal oxide semiconductor for controlling the current.

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JFET

Another type of FET, using a p-n junction.

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FET vs BJT

FETs are controlled by voltage, BJTs by current.

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MOSFET Circuit Symbols

MOSFET circuit symbols show the gate (G), source (S), and drain (D) connections of the MOSFET.

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JFET Circuit Symbols

JFET circuit symbols show the gate (G), source (S), and drain (D) connections of a JFET.

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Depletion Region (Diodes)

Naturally occurring area around a PN junction in a diode, even without an electric field, due to the movement of charge carriers.

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FET Types

FETs include MOSFETs, JFETs, MESFETs, and MODFETs. MOSFETs are the common type.

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Transistor

A 3-terminal electronic device made of semiconductor material used for amplification, switching, voltage regulation, and signal modulation.

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Vacuum tube

An electronic component used in circuits before transistors, bulky, fragile, and energy-intensive.

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Semiconductor Material

Material that can conduct electricity better than insulators but not as well as conductors, crucial for transistors.

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Doping (semiconductors)

Adding foreign elements to a semiconductor to change its electrical properties (positive or negative).

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P-type semiconductor

Semiconductor doped with elements that create "holes" increasing positive charge.

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N-type semiconductor

Semiconductor doped with elements that donate extra electrons, increasing negative charge.

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Diode (Forward Bias)

Current flows from the P-type to N-type material in a diode.

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Diode (Reverse Bias)

No current flows through the diode when this occurs; or voltage causes current to flow the opposite direction.

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Transistor Invention Year

Transistors were invented in 1947 at Bell Telephone Laboratories.

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Transistor Inventors

William Shockley, John Bardeen, and Walter Brattain developed the first transistors.

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FET vs. BJT: How are they different?

Field-Effect Transistors (FETs) use an electric field to control current flow in a channel, unlike Bipolar Junction Transistors (BJTs) which rely on a current flow in the base to control the flow from collector to emitter.

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What are the terminals of a FET?

A FET has three terminals: Source (S), Drain (D), and Gate (G). The Source and Drain form the ends of the channel and the Gate controls the channel conductivity.

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What is a depletion-type FET?

A depletion-type FET is inherently conductive when no voltage is applied to the gate. It's like an open switch in the 'ON' state.

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Enhancement-type FET

An enhancement-type FET is 'OFF' when no voltage is applied to the gate. It needs a voltage to be applied to the gate to turn 'ON' the channel conductivity.

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JFET vs. MOSFET

Both are FETs but have different construction. A JFET uses a PN junction to control the channel conductivity whereas a MOSFET uses an insulated gate.

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Power Transistors

These are transistors designed to handle higher current and voltage levels. They have additional material to help dissipate heat.

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What are the uses of transistors?

Transistors are used for switching, amplifying electronic signals, and as variable resistors.

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What is a common application of BJTs?

BJTs are used in amplifier circuits, where a small signal applied to the base controls a much larger current flow between the collector and emitter.

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What is the role of a resistor in the LED circuit?

The resistor limits the current flowing through the LED, preventing it from overheating and burning out.

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Why is a forward bias necessary for the base-emitter junction in the NPN BJT?

A forward bias allows current flow from emitter to collector, enabling the transistor to amplify or switch the signal.

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MOSFET State at 0 Gate Voltage

When the gate voltage is 0, no current flows between the source and drain. The channel region is depleted of electrons, acting as an insulator.

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Channel Formation in MOSFET

As gate voltage increases, electrons are attracted to the channel region between the source and drain. This builds up an electron-rich channel.

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Threshold Voltage

The gate voltage that needs to be exceeded to create a conductive channel. This is the point where enough electrons are gathered to form a connection between source and drain.

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Linear Region Operation

When the gate voltage is above the threshold voltage, the MOSFET operates in the linear (or triode) region. Current flows proportionally to the voltage between source and drain.

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Channel Length and Width

These physical dimensions of the MOSFET influence its characteristics. Length (L) is the distance between source and drain, while width (W) is the length of the source/drain.

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