Deck 5: Transistor Bias Circuits

Question 1

Refer to a)in the figure above. The most probable cause of trouble, if any, from these voltage measurements would be

A)RE is open.
B)the base- emitter junction is open.
C)a short from collector to emitter.
D)There are no problems.

Answer 1

A

Question 2

The most suitable biasing technique used is the

A)base- bias.
B)collector- bias.
C)emitter- bias.
D)voltage- divider bias.

Answer 2

D

Question 3

For linear operation, it is usual to set the Q- point so that

A)VCE = VCC.
B)VCE = VCC/2.
C)VCE = VE.
D)VCE = VCC/4.

Answer 3

B

Question 4

A certain transistor in a fixed- bias circuit has the following values: IB = 50 µA, fiDC = 125, VCC = 18 V, and RC = 1.2 k▲. VC is

A)10.5 V.
B)18 V.
C)0 V.
D)7.5 V.

Question 5

Base bias provides

A)a very unstable Q- point.
B)zero current in the base and collector circuits.
C)no current gain.
D)a very stable Q- point.

Question 6

A linear amplifier should have the Q- point located

A)in the distortion region.
B)close to saturation.
C)approximately half- way between saturation and cutoff.
D)close to cutoff.

Question 7

Refer to the figure above. If the transistor were replaced with a transistor whose fidc = 200, the change that might occur is

A)VC would change a small amount.
B)VC would increase to near 20 V.
C)IB would increase significantly.
D)VC would decrease to near 0 V.

Question 8

If a transistor operates at the middle of the dc load line, a decrease in the current gain will move the Q- point

A)off the load line.
B)down.
C)up.
D)nowhere.

Question 9

Refer to the figure above. If fiDC = 100, the minimum value of IB that would cause this transistor to saturate is

A)1 mA.
B)100 µA.
C)0.1 mA.
D)50 µA.

Question 10

Refer to the figure above. The voltage at the base of this silicon transistor is

A)0.3 V.
B)12 V.
C)0 V.
D)11.3 V.
E)0.7 V.

Question 11

If the base- emitter junction opens in a voltage- divider biased circuit, the emitter voltage will measure

A)0.7 V less than the base.
B)a voltage nearly equal to VCC.
C)0.7 V more than the base.
D)0 V.

Question 12

Saturation and cutoff are operating conditions that are very useful when operating the transistor as

A)a current amplifier.
B)a linear amplifier.
C)a switch.
D)None of the above.

Question 13

A circuit with a fixed emitter current is called

A)one- supply bias.
B)base- bias.
C)emitter- bias.
D)grid- bias.

Question 14

Adding an emitter resistor to a base- bias circuit produces a bias circuit called

A)base- emitter bias.
B)emitter- feedback bias.
C)emitter bias.
D)None of the above.

Question 15

Improper biasing can cause distortion in an amplifier's

A)output signal.
B)input signal.
C)frequency response.
D)power dissipation.

Question 16

The first step in analyzing emitter- biased circuits is to find the

A)base current.
B)collector current.
C)transistor power.
D)emitter voltage.

Question 17

Voltage- divider bias provides

A)an unstable Q- point.
B)a Q- point that easily varies with changes in the transistor's current gain.
C)a stable Q- point.
D)Both A and C above.

Question 18

Refer to d)in the figure above. The most probable cause of trouble, if any, from these voltage measurements is

A)a short from collector to emitter.
B)RE is open.
C)the base- emitter junction is open.
D)There are no problems.

Question 19

Refer to c)in the figure above. The most probable cause of trouble, if any, from these voltage measurements is

A)the base- emitter junction is open.
B)a short from collector to emitter.
C)RE is open.
D)There are no problems.

Question 20

Three different Q- points are shown on a dc load line. The upper Q- point represents the

A)cutoff point.
B)maximum current gain.
C)minimum current gain.
D)intermediate current gain.

Question 21

The emitter resistor in a voltage- divider bias circuit is open. The collector voltage will equal approximately

A)one- half VCC.
B)0 V.
C)VCC.
D)None of the above.

Question 22

If the collector resistor decreases to zero in a base- biased circuit, the load line will become

A)useless.
B)horizontal.
C)vertical.
D)flat.

Question 23

An indication of cutoff is that

A)VCE = 0 V.
B)IC = ICsat).
C)VCE = VCC.
D)VBE = 0.7 V.

Question 24

Refer to the figure above. The value of RC that will produce a value of VC = 10 V is

A)500 ▲.
B)1 k▲.
C)2.2 k▲.
D)2 k▲.

Question 25

Refer to the figure above. The purpose of RC is to

A)maintain VBE at 0.7 V.
B)stabilize the operating point with negative feedback.
C)develop the output voltage.
D)establish a dc base voltage.

Question 26

Two important yet easily measured quantities that can help determine if a transistor amplifier is operating correctly are

A)IC and VC.
B)fidc and IB.
C)VC and VBE.
D)VBE and IE.

Question 27

Refer to b)in the figure above. The most probable cause of trouble, if any, from these voltage measurements is

A)a short from collector to emitter.
B)RE is open.
C)the base- emitter junction is open.
D)There are no problems.

Question 28

The main difference between an NPN and PNP transistor amplifier is that

A)PNP transistors cannot amplify sine waves.
B)PNP transistors require opposite bias polarities as compared to NPN.
C)PNP transistors need more heat sinking.
D)NPN transistors are linear amplifiers, while PNP amplifiers are nonlinear.

Question 29

The Q- point of a two supply emitter- bias circuit is not affected by

A)current gain.
B)emitter resistance.
C)collector resistance.
D)VCC.

Question 30

On a dc load line, the area between saturation and cutoff is called the

A)saturation zone.
B)linear region.
C)depletion region.
D)breakdown region.

Question 31

Refer to the figure above. The purpose for R1 and R2 is to

A)maintain VBE at 0.7 V.
B)stabilize the operating point with negative feedback.
C)develop the output voltage.
D)establish a dc base voltage.

Question 32

For transistors using voltage- divider bias, the base current should be

A)much larger than the current through the voltage divider.
B)Beta times larger than the collector current.
C)about one- half the collector current.
D)much smaller than the current through the voltage divider.

Question 33

For a properly designed emitter- bias circuit, changes in current gain

A)affect the collector voltage.
B)severely affect the Q- point.
C)do not occur in the transistor.
D)do not affect the Q- point.