Deck 11: JFETS

Question 1

The transconductance curve of a JFET is a graph of drain current versus voltage gate to source.

Answer 1

True

Question 2

The JFET is a voltage-controlled device because an input voltage controls an output current.

Answer 2

True

Question 3

What is a circuit that steers one or more of the input signals to the output line?

A) dc amplifier
B) regulator
C) oscillator
D) multiplexer

Answer 3

D

Question 4

In order to produce a JFET,a manufacturer diffuses two areas of p-type semiconductor into the n-type semiconductor.

Question 5

A stage that isolates the preceding stage from the following stage is called a

A) chopper amplifier.
B) driver amplifier.
C) buffer amplifier.
D) preamplifier.

Question 6

In the schematic symbol for a p-channel JFET,the gate arrow points out.

Question 7

A slow shift in the final dc output voltage produced by minor changes in supply voltage,transistor parameters,and temperature variations is referred to as _________.

A) drift
B) transconductance
C) pinchoff
D) chopper

Question 8

Circuits that amplify frequencies down to 0 Hz are called

A) small-signal amplifiers.
B) narrowband amplifiers.
C) dc amplifiers.
D)tuned RF amplifiers.

Question 9

The current drain to source with a shorted gate (I_DSS )is the maximum drain current a JFET can produce.

Question 10

Gate bias is the best way to bias a JFET in the active region because the Q point is very stable.

Question 11

A JFET chopper can be used to build a dc amplifier.

Question 12

A circuit that generates an ac signal is

A) a rectifier.
B) an oscillator.
C) an oscilloscope.
D) a channel.

Question 13

A JFET common-source amplifier produces a noninverted output that is coupled from the drain.

Question 14

Transconductance tells us how effective the gate-source voltage is in controlling the source current.

Question 15

The unit mho is the ratio of current to voltage and the modern unit for mho is the siemen.

Question 16

The supply voltage (V_DD )for a JFET forces free electrons to flow from the drain to the source.

Question 17

JFET self-bias results when the circuit creates its own bias by using the voltage developed across the source resistor to reverse-bias the gate.

Question 18

A JFET analog switch operates either in the ohmic region or in the cutoff region.

Question 19

The source and drain terminals are interchangeable at high frequencies.

Question 20

The term field effect is related to the depletion layers around each p region of a JFET.

Question 21

Which amplifying device is preferred for most linear applications?

A) FET
B) BJT
C) triode
D) magnetron

Question 22

The almost-vertical part of the drain curve below pinchoff is called the

A) static region.
B) channel.
C) ohmic region.
D) saturation.

Question 23

The minimum JFET voltage V_P is called

A) cutoff voltage.
B) filtered voltage.
C) reverse voltage.
D) pinchoff voltage.

Question 24

In audio applications,JFETs are often used as

A) analog switches.
B) tuned RF amplifiers.
C) common-source amplifiers.
D) source followers.

Question 25

The power supply for a JFET forces free electrons to flow from

A) drain to source.
B) source to drain.
C) gate to source.
D) gate to drain.

Question 26

The JFET is a

A) voltage-controlled device.
B) current-controlled device.
C) bipolar device.
D) nonlinear device.

Question 27

What is the breakdown voltage as listed on the drain curves shown in Figure 11-5?

A) 0 V
B) 4 V
C) 15 V
D) 30 V

Question 28

Which instrument cannot be used in the testing of a JFET?

A) curve tracer
B) oscilloscope
C) watt meter
D) DMM

Question 29

Because of the large spread in JFET parameters,which method of biasing cannot be used?

A) gate
B) VDB
C) two supply
D) current source

Question 30

What is the pinchoff voltage as listed on the drain curves shown in Figure 11-5?

A) 0 V
B) - 1 V
C) 15 V
D) 4 V

Question 31

A graph of drain current versus voltage gate to source is called

A) drain curve.
B) transconductance curve.
C) gate curve.
D) conductance curve.

Question 32

To prevent unwanted changes in volume,most modern receivers use

A) automatic frequency control.
B) automatic gain control.
C) faders.
D) woofers.

Question 33

An entry shown on the data sheet that helps to determine the dc input resistance of a JFET is _________.

A) IGSS
B) VGS
C) I_D
D) R_S

Question 34

The current flowing from the JFET's source to drain must pass through what between the depletion layers?

A) gate
B) ground
C) channel
D) base

Question 35

The source and drain terminals are

A) changeable at high frequencies.
B) not changeable at high frequencies.
C) not changeable at low frequencies.
D) connected to the gate.

Question 36

A typical JFET has an input resistance of

A) about 200 ohms.
B) about 2000 ohms.
C) about 200 kΩ.
D) about 200 MΩ.

Question 37

With a JFET,the gate-source diode is

A) always reverse-biased.
B) always forward-biased.
C) is connected to the drain voltage.
D) is connected to ground.

Question 38

A JFET is a symmetrical device at low frequencies since

A) either end can act like a source or the drain.
B) either end can act like a source or the gate.
C) either end can act like a drain or the gate.
D) either end can act like the channel.

Question 39

Since the field-effect transistor depends on only one type of charge,it is referred to as _________.

A) unipolar
B) bipolar
C) singular
D) unilateral

Question 40

One of the most important pieces of information on the data sheet of a depletion-mode device is

A) derating factor.
B) reverse breakdown.
C) maximum drain current.
D) minimum gate to source voltage.

Question 41

What is the type of JFET circuit that has the ac signal coupled to the gate and the output taken from the drain?

A) common source
B) common drain
C) common gate
D) source follower

Question 42

Which JFET amplifier configuration exhibits a very high input impedance and low output impedance?

A) common source
B) common gate
C) source follower
D) drain follower

Question 43

How effective the gate-source voltage is controlling the drain current is referred to as _________.

A) pinchoff
B) saturation
C) transconductance
D) conductance

Question 44

What is unwanted disturbance superimposed on a useful signal?

A) alternating current
B) harmonics
C) chassis
D) noise

Question 45

A JFET circuit that converts a dc input voltage to a square-wave output is

A) a regulator.
B) a chopper.
C) an inverter.
D) a rectifier.

Question 46

What is the equivalent and modern unit for mho?

A) ohm
B) farad
C) siemen
D) henry

Question 47

Why is gate bias the worst method to bias a JFET in the active region?

A) because the operating point is too unstable
B) because the operating point is too stable
C) because the Q point is at pinchoff
D) because the gate is forward biased

Question 48

Self-biasing a JFET is used only with

A) small-signal amplifiers.
B) power amplifiers.
C) wideband amplifiers.
D) tuned RF amplifiers.

Question 49

The JFET source follower has

A) low input resistance.
B) high voltage gain.
C) a voltage gain less than one.
D) the output taken from the drain.

Question 50

When the JFET operates in only the ohmic region or in the cutoff region,it is being used as

A) an analog switch.
B) a linear amplifier.
C) an oscillator.
D) a regulator.