Deck 5: Transistor Bias Circuits

Question 1

Figure 1
Refer to Figure 1. The end points of the dc load line are at approximately

A)7 mA and 8 V
B)15 mA and 15 V
C)8 mA and 7 V
D)0 mA and 15 V

Answer 1

B

Question 2

At cutoff,

A)VCE = VCC
B)VB = 0.7 V
C)IC = IC(sat)
D)VCE = 1/2 VCC

Answer 2

A

Question 3

Figure 4
Refer to Figure 4. Assume you were troubleshooting and found that VE is exactly the same as VEE. The trouble could be caused by

A)shorted RC
B)open RB
C)open R_E
D)any of the above

Answer 3

B

Question 4

Figure 4
Refer to Figure 4. The emitter voltage, VE is approximately

A)-6.4 V
B)-3.8 V
C)-5.2 V
D)-1.4 V

Question 5

Figure 7
Refer to Figure 3. Note the transistor is a pnp type. The value of IC is approximately

A)1.0 mA
B)3.4 mA
C)2.5 mA
D)1.3 mA

Question 6

Figure 5 (This is similar to Figure 4 but uses a pnp transistor with the same fi.)
Refer to Figure 5. If RB is increased, VE will

A)decrease
B)increase
C)not change

Question 7

Refer to Figure 6. Assume VC = 0.07 V and VB = 0.7 V. The fault may be that

A)VCC has dropped to 8 V
B)RC is open
C)V_CC is open
D)R_E is open

Question 8

Assume a pnp transistor is used in a voltage- divider biased circuit. If VB = -2.8 V, VE should be

A)+3.5 V
B)- 3.5 V
C)- 2.1 V
D)- 2.8 V

Question 9

Figure 1
Refer to Figure 1. The Q- point is approximately at

A)6.6 mA and 8.4 V
B)8.4 mA and 6.6 V
C)8.4 mA and 8.4 V
D)6.6 mA and 6.6 V

Question 10

Figure 5 (This is similar to Figure 4 but uses a pnp transistor with the same fi.)
Refer to Figure 5. The expected emitter voltage is

A)the same as the collector voltage in the npn circuit
B)the same as the npn circuit
C)the same as the collector voltage in the npn circuit except for the sign
D)the same as the npn circuit except for the sign

Question 11

Figure 7
Refer to Figure 7. Assume the thermistor has a resistance of 1.7 k▲. VOUT is approximately

A)5.9 V
B)4.7 V
C)7.5 V
D)5.4 V

Question 12

A stiff voltage divider is one in which

A)the Q- point will be centered
B)has very large bias resistors
C)loading effects can be ignored
D)two voltage sources are used

Question 13

Assume a load line is drawn for a transistor amplifier. If VCC is increased, the load line will

A)have a higher cutoff voltage
B)have a higher saturation current
C)both A and B
D)none of the above

Question 14

Figure 7
Refer to Figure 7. The input resistance of RIN(BASE)

A)depends on the fi of the transistor
B)depends on the resistance of RE
C)both A and B
D)none of the above

Question 15

Figure 2
Refer to Figure 2. VCE is approximately

A)5.3 V
B)8.5 V
C)3.2 V
D)6.6 V

Question 16

Figure 5 (This is similar to Figure 4 but uses a pnp transistor with the same fi.)
Refer to Figure 5. If RC is replaced with a 1.5 k▲ resistor, you would expect to see a large change in

A)IE
B)VE
C)VCE
D)all of the above

Question 17

Of the methods shown below, the one that has the most stability is

A)collector feedback bias
B)base bias
C)emitter bias
D)emitter feedback bias

Question 18

Figure 2
Refer to Figure 2. The value of IC is approximately

A)2.6 mA
B)3.3 mA
C)1.3 mA
D)2.0 mA

Question 19

Figure 5 (This is similar to Figure 4 but uses a pnp transistor with the same fi.)
Refer to Figure 5. If the transistor is replaced with a lower fi one, there will be

A)a small increase in IE
B)a large change in IE
C)a small decrease in I_E
D)no change in I_E

Question 20

Figure 4
Refer to Figure 4. The type of bias shown is

A)emitter bias
B)collector feedback bias
C)emitter- feedback bias
D)dual supply base bias

Question 21

IC and IE are nearly the same in a properly biased transistor.

Question 22

Voltage- divider bias requires two power supplies.

Question 23

Figure 4
Refer to Figure 4. If you wanted to develop the equation for IE,

A)assume VCE = VRC; apply Ohm's law to find IC first; then solve for IE
B)write KVL around the base- emitter circuit
C)Thevenize the base input circuit and apply Ohm's law
D)write KVL through the emitter and collector and both power supplies

Question 24

RIN(BASE)will increase if IE decreases.

Question 25

The dc load line is a straight line drawn from IC(sat)to VCC.

Question 26

Base bias is more stable than voltage- divider bias.

Question 27

Collector feedback bias uses a form of negative feedback.

Question 28

VBE of properly biased pnp transistor is a positive value.

Question 29

Assume the output of an amplifier has both peaks clipped. This can be caused by

A)too little gain
B)Q- point is not centered
C)power supply voltage is too high
D)all of the above

Question 30

The Q- point can be anywhere along the dc load line.

Question 31

Figure 5 (This is similar to Figure 4 but uses a pnp transistor with the same fi.)
Refer to Figure 5. If RB is increased, VCE will

A)decrease
B)increase
C)not change