Question 1

JFETs are

Accepted Answer

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

Question 2

-The amplifier has low input impedance, high output impedance, and high voltage gain.

Accepted Answer

A)  common-gate 
B)  common-drain 
C)  common-source

Question 3

A given JFET has values of gm0 = 1200 μs and VGSoff) = -4 V. What is the approximate value of IDSS?

Accepted Answer

A)  4.8 mA 
B)  9.6 mA 
C)  2.4 mA 
D)  Cannot be determined with the information given.

Question 4

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

Accepted Answer

A)  less than 
B)  equal to 
C)  less than or equal to 
D)  greater than

Question 5

In a JFET amplifier, VGS = -2 V and ID = IDSS. Which of the following statements is true?

Accepted Answer

A)  The gate terminal of the JFET is probably open. 
B)  The gate-source junction of the JFET is probably shorted. 
C)  The drain terminal of the JFET is probably open. 
D)  The readings do not indicate that any problem exists.

Question 6

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

Accepted Answer

A)  gate 
B)  drain 
C)  source

Question 7

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

Accepted Answer

A)  the constant-voltage region. 
B)  the ohmic region. 
C)  the constant-current region. 
D)  Both B and C above.

Question 8

The high input impedance of a JFET amplifier prevents it from being used as a buffer.

Accepted Answer

A) True 
 B)False

Question 9

Gate-source breakdown voltage can be defined as

Accepted Answer

A)  the value gate-source voltage that will allow the channel to break down and conduct. 
B)  the value of gate-source voltage that will damage the JFET. 
C)  the maximum allowable value of VGS. 
D)  None of the above.
Chapter 12 Field-Effect Transistors Answer Key

Question 10

-Assume that the JFET has values of IDSS = 12 mA and VGSoff) = -6 V. If VGG = -3 V, what is the value of ID for the circuit?

Accepted Answer

A)  1 mA 
B)  3 mA 
C)  4.55 mA 
D)  6 mA

Question 11

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?

Accepted Answer

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.

Question 12

Which of the following statements is true?

Accepted Answer

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.

Exam 12: Field-Effect Transistors