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Questions and Answers
Questions and Answers
What is the primary function of a transistor?
What is the primary function of a transistor?
- To control current flow with a small electrical signal (correct)
- To store electrical energy
- To generate electrical power
- To act as a passive resistor in a circuit
Which family of transistors uses a small voltage to control a larger current?
Which family of transistors uses a small voltage to control a larger current?
- Neither BJTs nor FETs
- Bipolar Junction Transistors (BJTs)
- Field-Effect Transistors (FETs) (correct)
- Both BJTs and FETs equally
What distinguishes FETs from BJTs in terms of charge carriers?
What distinguishes FETs from BJTs in terms of charge carriers?
- FETs use only majority charge carriers (electrons or holes), while BJTs use both. (correct)
- BJTs use only majority charge carriers, while FETs use both.
- FETs use both electrons and holes, while BJTs use only electrons.
- Both FETs and BJTs use both types of charge carriers equally.
In an N-channel JFET, what type of charge carriers are responsible for current flow?
In an N-channel JFET, what type of charge carriers are responsible for current flow?
What is the function of the gate terminal in a JFET?
What is the function of the gate terminal in a JFET?
Within a JFET, where does the majority of charge carriers flow?
Within a JFET, where does the majority of charge carriers flow?
What determines whether a JFET is classified as n-channel or p-channel?
What determines whether a JFET is classified as n-channel or p-channel?
Which terminal introduces majority charge carriers into the FET?
Which terminal introduces majority charge carriers into the FET?
What is the primary function of the drain terminal in a FET?
What is the primary function of the drain terminal in a FET?
How is the gate terminal formed in a JFET?
How is the gate terminal formed in a JFET?
What is the state of a JFET when no voltage is applied (VDS = 0 and VGS = 0)?
What is the state of a JFET when no voltage is applied (VDS = 0 and VGS = 0)?
What happens when VDS is applied and VGS = 0 in an N-channel JFET?
What happens when VDS is applied and VGS = 0 in an N-channel JFET?
What is the effect of applying a negative VGS on an N-channel JFET?
What is the effect of applying a negative VGS on an N-channel JFET?
What is meant by the 'pinch-off voltage' ($V_p$) in a JFET?
What is meant by the 'pinch-off voltage' ($V_p$) in a JFET?
What happens to the drain current ($I_{DS}$) when $V_{DS}$ exceeds $V_p$ (pinch-off voltage)?
What happens to the drain current ($I_{DS}$) when $V_{DS}$ exceeds $V_p$ (pinch-off voltage)?
In the output characteristics of a JFET, what does the Ohmic region indicate?
In the output characteristics of a JFET, what does the Ohmic region indicate?
In a JFET, what condition defines the cut-off region?
In a JFET, what condition defines the cut-off region?
What is the primary characteristic of the saturation or active region of a JFET?
What is the primary characteristic of the saturation or active region of a JFET?
What occurs in the breakdown region of a JFET?
What occurs in the breakdown region of a JFET?
How does the behavior of a P-channel JFET differ from that of an N-channel JFET regarding the influence of gate-source voltage ($V_{GS}$)?
How does the behavior of a P-channel JFET differ from that of an N-channel JFET regarding the influence of gate-source voltage ($V_{GS}$)?
What condition must be met for the drain current ($I_D$) in a JFET to be zero?
What condition must be met for the drain current ($I_D$) in a JFET to be zero?
If a JFET has a drain current $I_{DSS}$ when $V_{GS} = 0$, how is drain current ($I_D$) at the active region related to $I_{DSS}$, $V_{GS}$, and $V_P$?
If a JFET has a drain current $I_{DSS}$ when $V_{GS} = 0$, how is drain current ($I_D$) at the active region related to $I_{DSS}$, $V_{GS}$, and $V_P$?
In a JFET, how is the drain-source channel resistance ($R_{DS}$) calculated if you know the drain-source voltage ($V_{DS}$) and drain current ($I_D$)?
In a JFET, how is the drain-source channel resistance ($R_{DS}$) calculated if you know the drain-source voltage ($V_{DS}$) and drain current ($I_D$)?
What does the term 'transconductance gain' ($g_m$) represent in a JFET?
What does the term 'transconductance gain' ($g_m$) represent in a JFET?
What is the formula for the amplification factor ($\mu$) of a JFET, given the drain voltage ($V_{DS}$) and gate voltage ($V_{GS}$)?
What is the formula for the amplification factor ($\mu$) of a JFET, given the drain voltage ($V_{DS}$) and gate voltage ($V_{GS}$)?
What is the primary purpose of analyzing the transfer characteristics of a JFET?
What is the primary purpose of analyzing the transfer characteristics of a JFET?
What does the bottom end of a JFET transfer characteristic curve represent?
What does the bottom end of a JFET transfer characteristic curve represent?
What quantity does the top end of a JFET transfer characteristic curve typically represent?
What quantity does the top end of a JFET transfer characteristic curve typically represent?
In a JFET, if the transfer characteristic curve is expressed by the equation $I_D = I_{DSS}(1 - V_{GS}/V_{GS(off)})^2$, what can be inferred about JFETs?
In a JFET, if the transfer characteristic curve is expressed by the equation $I_D = I_{DSS}(1 - V_{GS}/V_{GS(off)})^2$, what can be inferred about JFETs?
Which of the following characteristics is generally true for JFETs compared to BJTs?
Which of the following characteristics is generally true for JFETs compared to BJTs?
For what type of applications are JFETs generally preferred over BJTs?
For what type of applications are JFETs generally preferred over BJTs?
Which of the following generally applies to JFETs in comparison to BJTs?
Which of the following generally applies to JFETs in comparison to BJTs?
In terms of output impedance, how do JFETs typically compare to BJTs?
In terms of output impedance, how do JFETs typically compare to BJTs?
How does the switching time of a JFET generally compare to that of a BJT?
How does the switching time of a JFET generally compare to that of a BJT?
How does power consumption generally compare between JFETs and BJTs?
How does power consumption generally compare between JFETs and BJTs?
What is a key structural difference between a MOSFET and a JFET?
What is a key structural difference between a MOSFET and a JFET?
What insulates the gate of a MOSFET from its channel?
What insulates the gate of a MOSFET from its channel?
Which type of MOSFET is more widely used in general applications?
Which type of MOSFET is more widely used in general applications?
At what gate-source voltage ($V_{GS}$) are depletion mode MOSFETs generally ON?
At what gate-source voltage ($V_{GS}$) are depletion mode MOSFETs generally ON?
What happens in a depletion MOSFET when $V_{GS}$ is -ve with respect to the substrate?
What happens in a depletion MOSFET when $V_{GS}$ is -ve with respect to the substrate?
What is the mode of operation called when a depletion MOSFET has too much negative Gate voltage to "pinch-off the channel"?
What is the mode of operation called when a depletion MOSFET has too much negative Gate voltage to "pinch-off the channel"?
What charge carriers does the Gate attract when $V_{GS}$ = +ve is applied to a MOSFET?
What charge carriers does the Gate attract when $V_{GS}$ = +ve is applied to a MOSFET?
Which term describes the MOSFET operation when Gate attracts the negative charge carriers from the P-substrate to the N channel?
Which term describes the MOSFET operation when Gate attracts the negative charge carriers from the P-substrate to the N channel?
What is the minimum gate-source voltage ($V_{GS}$) required to form the induced N-channel in an E-MOSFET (Enhancement-mode MOSFET) called?
What is the minimum gate-source voltage ($V_{GS}$) required to form the induced N-channel in an E-MOSFET (Enhancement-mode MOSFET) called?
What is the typical state of an E-MOSFET (Enhancement-mode MOSFET) when $V_{GS} = 0V$?
What is the typical state of an E-MOSFET (Enhancement-mode MOSFET) when $V_{GS} = 0V$?
In an E-MOSFET, what happens to the induced N channel if the value of $V_{GS}$ exceeds $V_{GS(th)}$?
In an E-MOSFET, what happens to the induced N channel if the value of $V_{GS}$ exceeds $V_{GS(th)}$?
Under what condition is the channel in an E-MOSFET said to be cut-off?
Under what condition is the channel in an E-MOSFET said to be cut-off?
What condition applies to the drain current ($I_D$) when VGS is less than VGS(th) in an E-MOSFET (Enhancement-mode MOSFET)?
What condition applies to the drain current ($I_D$) when VGS is less than VGS(th) in an E-MOSFET (Enhancement-mode MOSFET)?
Questions and Answers
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Flashcards
Flashcards
What is a transistor?
What is a transistor?
Semiconductor device that controls current using a small electrical signal.
What are BJTs?
What are BJTs?
Transistors which utilize a small current to control a large current.
What are FETs?
What are FETs?
Transistors which utilize a small voltage to control a current.
What does it mean for FETs to be unipolar?
What does it mean for FETs to be unipolar?
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What is a JFET?
What is a JFET?
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What are the 4 FET components?
What are the 4 FET components?
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What is a FET channel?
What is a FET channel?
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What is a FET source?
What is a FET source?
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What is a FET drain?
What is a FET drain?
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What is a FET gate?
What is a FET gate?
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What is the condition in a JFET when no voltage is applied?
What is the condition in a JFET when no voltage is applied?
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What happens when Vds is applied?
What happens when Vds is applied?
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What happens when Vgs is negative?
What happens when Vgs is negative?
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What is pinch-off voltage (Vp)?
What is pinch-off voltage (Vp)?
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What happens to current when Vds = Vp?
What happens to current when Vds = Vp?
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What is the ohmic region of a JFET?
What is the ohmic region of a JFET?
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What is the cut-off region of a JFET?
What is the cut-off region of a JFET?
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What is the saturation/active region of a JFET?
What is the saturation/active region of a JFET?
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What is the breakdown region of a JFET?
What is the breakdown region of a JFET?
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Transconductance Gain (gm)
Transconductance Gain (gm)
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Amplification Factor (μ)
Amplification Factor (μ)
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What is the Transfer Characteristic of a JFET?
What is the Transfer Characteristic of a JFET?
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What is unique about MOSFETs?
What is unique about MOSFETs?
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What are the two basic MOSFET types?
What are the two basic MOSFET types?
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How are depletion mode MOSFETs are generally ON?
How are depletion mode MOSFETs are generally ON?
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What happens when Vas = -ve in a D-MOSFET?
What happens when Vas = -ve in a D-MOSFET?
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What happens when Vgs = +ve in a D-MOSFET?
What happens when Vgs = +ve in a D-MOSFET?
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What is the threshold voltage Vgs(th)?
What is the threshold voltage Vgs(th)?
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What happens when VGS = 0V in E-MOSFET?
What happens when VGS = 0V in E-MOSFET?
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Describe E-MOSFET operation
Describe E-MOSFET operation
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When does a E-MOSFET enters cut-off?
When does a E-MOSFET enters cut-off?
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Study Notes
Study Notes
- The document comprises study notes for Basic Electronics, specifically Module 2, taught by Faculty Tejashree S (Scheme: 2022)
- The syllabus includes bipolar junction transistors (BJTs) and field-effect transistors (FETs).
Introduction to Transistors
- A transistor controls current using a small electrical signal.
- Transistors are mainly divided into bipolar and field-effect families.
- BJTs use current to control a larger current.
- FETs use voltage to control current.
Field-Effect Transistors (FETs)
- FETs are unipolar rather than bipolar components.
- Current through FETs involves either electrons (N-channel) or holes (P-channel).
- In JFETs, controlled current flows between the Source and Drain.
- The controlling voltage is applied between the Gate and Source
- The current in JFET channel relies on the Gate terminal input voltage.
- FETs are available in two types: JFETs (Junction Field Effect Transistors) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).
Junction Field Effect Transistors (JFETs)
- JFETs are voltage-controlled, three-terminal unipolar semiconductor devices.
- A JFET contains a Source (S), Gate (G), and Drain (D).
- Voltage applied to the Gate with respect to the Source (VGS) controls current between the Drain and Source.
- JFET types depend on charge flow: (i) n-channel JFET (electrons) and (ii) p-channel JFET (holes).
FET Components
- Channel: Majority charge carriers flow in it, facilitating movement from source to drain.
- Source: The terminal where majority charge carriers enter the FET.
- Drain: The collecting terminal for majority charge carriers contributing to conduction.
- Gate: Formed by semiconductor diffusion to create a high impurity region, controlling carrier flow.
N-Channel JFET Operation
- Case I (VDS = 0, VGS = 0): The device is idle, and no current flows (IDS = 0).
- Case II (VDS applied, VGS = 0):
- PN junctions create depletion layers on N-channel sides.
- Electrons flow from Source to Drain through the channel between depletion layers.
- Depletion layer size determines channel width and IDS.
- Case III (VDS applied, VGS = -ve):
- The increased depletion region reduces the conducting channel.
- Increasing resistance reduces Source-to-Drain current.
- Greater (-VGS) further reduces channel width, leading to pinch-off voltage (VP).
- At pinch-off, IDS is limited by channel resistance until VDS reaches VP, where saturation occurs at IDSS
JFET Output Characteristics (Drain) V-I Curves
- Ohmic Region: At VGS = 0, the depletion region is small, and the JFET acts as a voltage-controlled resistor.
- Cut-off Region: Also known as the pinch-off region, VGS causes the JFET to act as an open circuit with max channel resistance.
- Saturation or Active Region: The JFET conducts well controlled by VGS, while VDS has minimal effect.
- Breakdown Region: High VDS causes the JFET's resistive channel to break down, allowing uncontrolled max current.
P-Channel JFET Characteristics
- Characteristics are similar to N-channel JFETs, but drain current ID decreases as positive gate-source voltage VGS increases.
Active Region Drain Current
- Drain current, ID is zero when VGS = VP; for typical operation, VGS is between VP and 0.
- Drain current, ID in the active region is defined.
Drain-Source Channel Resistance
- Drain-source channel resistance (RDS)
Transconductance Gain
- gm is the rate of change of ID (drain current) with respect to the change in VGS (gate-source voltage).
Amplification Factor
- Amplification factor (μ) is defined
JFET Transfer Characteristics
- Transfer characteristics for changes in ID due to VGS variation with constant VDS
- At VGS axis equals VGS(off), and on the ID axis equal to IDss.
- When VGS = VGS(off), ID = 0.
- When VGS = 0, ID = IDSS.
JFET Square-Law Devices
- JFETs are often referred to as square-law devices
BJT vs FET Comparison
- BJT: Bipolar junction transistor, low input impedance, current control, noisy, temperature-dependent, cheaper, larger.
- FET: Unipolar junction transistor, high input impedance, voltage control, less noisy, better heat stability, costly, smaller.
- BJT: High output impedance, high voltage gain, low current gain, medium switching time, consumes more power.
- FET: Low output impedance, low voltage gain, high current gain, fast switching time, consumes less power.
Metal Oxide Semiconductor Field Effect Transistor (MOSFET)
- MOSFET lacks the pn junction structure; the gate is insulated from the channel by a silicon dioxide (SiO2) layer.
- MOSFETs are used for switching and amplifying electronic signals, suitable for ICs due to small chip size.
- MOSFETs have two types: Enhancement (E-MOSFET) and Depletion (D-MOSFET); enhancement type is more common.
MOSFET Operation
- Depletion mode MOSFETs are ON at VGS = 0V; drain current is linked to the source current
- Channel conductivity in depletion MOSFETs is lower compared to enhancement MOSFETs
- Case I (VGS = 0): Max current flows
- Case II (VGS = -ve): Gate repels electrons, forming a depletion region that increases resistance and reduces drain current
- Too much negative gate can pinch-off the channel for OFF state
- Case III (VGS = +ve): Gate attracts negative carriers, reducing channel resistance and increasing drain current; referred to as enhancement-mode.
E-MOSFET
- Conductivity depends on positive gate bias
- The device is also an enchancement MOSFET
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