Question 1

The terminal is the JFET counterpart of the BJT base terminal.
A) gate
B) drain
C) source

Accepted Answer

The gate terminal in a JFET (Junction Field-Effect Transistor) serves a similar function to the base terminal in a BJT (Bipolar Junction Transistor), controlling the flow of current through the device.

Question 2

JFETs are
A) current-controlled devices.
B) voltage-controlled devices.
C) frequency-controlled devices.
D) impedance-controlled devices.

Accepted Answer

JFETs (Junction Field-Effect Transistors) are voltage-controlled devices, where the input voltage controls the current flow through the device.

Question 3

A JFET has the following ratings: VGSoff) = -2 V to -5 V and IDSS = 4 mA to 12 mA. The device is being used in a voltage divider circuit. When the load line is plotted, it is found that the VGS for the circuit has a range of -1 V to -3.5 V. What are the corresponding Qmax) values?
A) VGSQ = -1 V, IDQ = 7.68 mA
B) VGSQ = -3.5 V, IDQ = 1.1 mA
C) VGSQ = -1 V, IDQ = 1 mA
D) Cannot be determined with the information given.

Accepted Answer

B

Question 4

A JFET has values of IDSS = 12 mA and VGSoff) = -4 V. What is the value of ID at VGS = -8 V?
A) 12 mA
B) 0 mA
C) 4 mA
D) 2 mA

Accepted Answer

When $V_{GS}$ is less than $V_{GS(off)}$, the JFET is completely off, and the drain current $I_D$ is 0 mA. Since $-8V < -4V$, the JFET is off.

Question 5

The value of gm is always the value of gm0 for a given JFET.
A) less than
B) equal to
C) less than or equal to
D) greater than

Accepted Answer

The value of gm (transconductance) for a given JFET can be less than or equal to gm0 (maximum transconductance) depending on the operating point of the JFET. At maximum drain current (Idss), gm equals gm0, but it decreases with the decrease in drain current as the JFET moves away from its ideal operating point.

Question 6

The region of the JFET drain curve that lies between pinchoff and breakdown is called
A) the constant-voltage region.
B) the ohmic region.
C) the constant-current region.
D) Both B and C above.

Accepted Answer

The region of the JFET drain curve that lies between pinchoff and breakdown is called the constant-current region, because in this region, the current through the device remains relatively constant despite changes in the drain-source voltage.

Question 7

A JFET has the following ratings: VGSoff) = -2 V to -5 V and IDSS = 4 mA to 12 mA. This device is being used in a self-bias circuit. When the bias line for the device is plotted, it is found that VGS for the circuit will have a range of -1 V to -2.5 V. What are the corresponding Qmin) values?
A) VGSQ = -1 V, IDQ = 1 mA
B) VGSQ = -2.5 V, IDQ = 250 μA
C) VGSQ = -1 V, IDQ = 7.86 mA
D) Cannot be determined with the information given.

Accepted Answer

The correct answer is A because the bias line is within the range of VGSoff) and IDSS, so the device is operating in the saturation region. In the saturation region, ID is independent of VGS, so IDQ will be equal to IDSS.

Question 8

The value of ID is always the value of IDSS for a given JFET.
A) less than
B) equal to
C) less than or equal to
D) greater than

Accepted Answer

The value of ID (drain current) for a given JFET can be less than or equal to IDSS (the maximum drain current for a JFET when the gate-source voltage is 0V), depending on the gate-source voltage applied.

Question 9

Which of the following is usually used to control the channel width of a given JFET?
A) VS
B) VGS
C) The operating frequency
D) ID

Accepted Answer

The channel width of a Junction Field Effect Transistor (JFET) is primarily controlled by the gate-source voltage (VGS). Adjusting VGS varies the electric field in the channel, which in turn modulates the channel's conductivity and width.

Question 10

As the channel width of a JFET decreases, the source-to-drain resistance of the device
A) increases.
B) decreases.

Accepted Answer

As the channel width of a JFET decreases, the path available for current flow also decreases, leading to an increase in the source-to-drain resistance. This is because a narrower channel restricts the flow of charge carriers, making it harder for current to pass through, which effectively increases the resistance.

Question 11

A JFET has values of IDSS = 10 mA and VGSoff) = -5 V. What is the value of ID at VGS = -3 V?
A) 1.6 mA
B) 3.6 mA
C) 25.6 mA
D) 4 mA

Accepted Answer

ID = IDSS * (1 - VGS/VGSoff)^2 = 10 mA * (1 - (-3 V)/(-5 V))^2 = 1.6 mA

Question 12

A JFET has the following ratings: VGSoff) = -2 V to -5 V and IDSS = 4 mA to 12 mA. The device is being used in a gate bias circuit with a gate supply voltage of VGG = -1 V. What is the difference between the minimum and maximum values of ID for the circuit?
A) 7.68 mA
B) 9.6 mA
C) 6.68 mA
D) 8.6 mA

Accepted Answer

The answer of A JFET has the following ratings: VGSoff)...

Question 13

The value of VDS that causes ID to reach its maximum value at a constant value of VGS is called
A) VDmax).
B) pinchoff voltage.
C) VDSS.
D) None of these is correct.

Accepted Answer

The pinchoff voltage is the value of VDS at which the drain current ID reaches its maximum value for a given constant value of VGS in a field-effect transistor (FET). At this point, the channel is fully depleted at the drain end, preventing any further increase in current despite increases in VDS.

Question 14

A given JFET has values of Vp = +10 V and IDSS = 8 mA. What is the value of VGSoff) for the device?
A) +10 V
B) -10 V
C) -5 V
D) Cannot be determined from the information given.

Accepted Answer

VGS(off) is the gate-source voltage at which the JFET channel is completely pinched off, and it is equal to Vp. Since Vp is given as +10 V, VGS(off) would be -10 V because Vp is defined as a negative value for an n-channel JFET and a positive value for a p-channel JFET, indicating the polarity of the gate-source voltage required to completely turn off the channel.

Question 15

Which of the JFET biasing circuits listed below provides the best Q-point stability?
A) Gate-bias
B) Self-bias
C) Voltage-divider bias
D) Current-source bias

Accepted Answer

Current-source bias provides the best Q-point stability because it uses a constant current source to bias the JFET, which results in a stable Q-point even when the JFET parameters or the supply voltage change.

Question 16

Which of the following statements is true?
A) JFET drain current is controlled by its input gate) current.
B) JFET channel width is controlled by its gate-source voltage.
C) There is only one way to vary JFET channel width.
D) JFET drain current at a given drain supply voltage) varies inversely with channel width.

Accepted Answer

The JFET channel width is controlled by its gate-source voltage, which affects the depletion region and thus the current flow.

Question 17

The terminal is the JFET counterpart of the BJT emitter terminal.
A) gate
B) drain
C) source

Accepted Answer

The source terminal in a JFET (Junction Field-Effect Transistor) is analogous to the emitter terminal in a BJT (Bipolar Junction Transistor). Both serve as the primary terminal through which carriers (electrons or holes) enter the device.

Question 18

A given JFET has values of gm0 = 1200 μS and VGSoff) = -4 V. What is the value of gm for the device at VGS = -2 V?
A) 600 μS
B) 1200 μS
C) 300 μS
D) Cannot be determined with the information given.

Accepted Answer

The transconductance (gm) for a JFET can be calculated using the formula gm = gm0 * (1 - VGS/VGSoff), where gm0 is the maximum transconductance, VGS is the gate-source voltage, and VGSoff is the gate-source cutoff voltage. Plugging in the given values: gm = 1200 μS * (1 - (-2)/(-4)) = 1200 μS * 0.5 = 600 μS.

Question 19

The terminal is the JFET counterpart of the BJT collector terminal.
A) gate
B) drain
C) source

Accepted Answer

The drain terminal in a JFET is analogous to the collector terminal in a BJT, as both are the terminals through which the main current flows out of the device.

Question 20

The JFET uses a positive drain supply voltage VDD).
A) n-channel
B) p-channel

Accepted Answer

n-channel JFETs use a positive drain supply voltage (VDD) to operate, as they are constructed with n-type semiconductor material and require a positive voltage for proper operation.

Quiz 12: Field-Effect Transistors

The terminal is the JFET counterpart of the BJT base terminal.

JFETs are

A JFET has the following ratings: VGSoff) = -2 V to -5 V and IDSS = 4 mA to 12 mA. The device is being used in a voltage divider circuit. When the load line is plotted, it is found that the VGS for the circuit has a range of -1 V to -3.5 V. What are the corresponding Qmax) values?

A JFET has values of IDSS = 12 mA and VGSoff) = -4 V. What is the value of ID at VGS = -8 V?

The value of gm is always the value of gm0 for a given JFET.

The region of the JFET drain curve that lies between pinchoff and breakdown is called

A JFET has the following ratings: VGSoff) = -2 V to -5 V and IDSS = 4 mA to 12 mA. This device is being used in a self-bias circuit. When the bias line for the device is plotted, it is found that VGS for the circuit will have a range of -1 V to -2.5 V. What are the corresponding Qmin) values?

The value of ID is always the value of IDSS for a given JFET.

Which of the following is usually used to control the channel width of a given JFET?

As the channel width of a JFET decreases, the source-to-drain resistance of the device

A JFET has values of IDSS = 10 mA and VGSoff) = -5 V. What is the value of ID at VGS = -3 V?

A JFET has the following ratings: VGSoff) = -2 V to -5 V and IDSS = 4 mA to 12 mA. The device is being used in a gate bias circuit with a gate supply voltage of VGG = -1 V. What is the difference between the minimum and maximum values of ID for the circuit?

The value of VDS that causes ID to reach its maximum value at a constant value of VGS is called

A given JFET has values of Vp = +10 V and IDSS = 8 mA. What is the value of VGSoff) for the device?

Which of the JFET biasing circuits listed below provides the best Q-point stability?

Which of the following statements is true?

The terminal is the JFET counterpart of the BJT emitter terminal.

A given JFET has values of gm0 = 1200 μS and VGSoff) = -4 V. What is the value of gm for the device at VGS = -2 V?

The terminal is the JFET counterpart of the BJT collector terminal.

The JFET uses a positive drain supply voltage VDD) .