Deck 4: Bipolar Junction Transistors

Question 1

The NOR gate is a digital circuit that produces a

A)HIGH level signal when one or more inputs are LOW
B)LOW level signal when one or more inputs are LOW
C)LOW level signal when one or more inputs are HIGH
D)HIGH level signal when one or more inputs are HIGH

Answer 1

C

Question 2

Figure 6 A phototransistor and its characteristic curve
Refer to Figure 6. Assume you measure VOUT as 11 V. From this, you can conclude that the light intensity is approximately

A)20 mW/cm2
B)10 mW/cm2
C)40 mW/cm2
D)30 mW/cm2

Answer 2

A

Question 3

A 10 mV ac signal is applied to the base of a properly biased transistor with RC = 1.2 k▲ and re' = 36 ▲. The output ac voltage is

A)333 mV
B)33 mV
C)152 mV
D)105 mV

Answer 3

B

Question 4

Small signal transistors are available in

A)dual in line (DIP)packs
B)plastic or metal cases
C)quad small outline (SO)packs
D)all of the above

Question 5

For the characteristic curve in Figure 2, the equation IC = fiDCIB is true

A)only beyond C on the curve
B)at no place on the curve
C)only between B and C on the curve
D)only between A and B on the curve

Question 6

Figure 2 A characteristic curve
For the characteristic curve in Figure 2, the region between A and B is called the

A)active region
B)breakdown region
C)saturation region
D)cutoff region

Question 7

The primary purpose of an optocoupler is to

A)couple an LED to a relay
B)amplify light
C)convert light into electrical current
D)isolate certain sections of circuits

Question 8

Figure 4
Refer to Figure 4. If RB = 100 k▲, VC is approximately

A)5 V
B)7.5 V
C)12.5 V
D)10 V

Question 9

The NAND gate is a digital circuit that produces a

A)LOW level signal when both inputs are LOW
B)HIGH level signal when both inputs are LOW
C)HIGH level signal when both inputs are HIGH
D)LOW level signal when both inputs are HIGH

Question 10

Figure 5
Refer to Figure 5. When conducting, assume the LED drops 1.8 V and VCE(sat)= 0.2 V. If the input square wave is +3.0 V, the current in the LED will be approximately

A)30 mA
B)24 mA
C)105 mA
D)136 mA

Question 11

A forward- biased npn transistor has a typical voltage drop from base to emitter of

A)50 V
B)10 V
C)0.7 V
D)1.5 V

Question 12

In a certain BJT, the collector current is 22.0 mA when the base current is 100 µA. The emitter current is

A)21.9 mA
B)22.1 mA
C)22.0 mA
D)2.2 mA

Question 13

Figure 7
Refer to Figure 7. The transistor is

A)cutoff
B)in the breakdown region
C)in the active region
D)saturated

Question 14

If a BJT is saturated,

A)VCC appears between the collector and emitter
B)both base current and collector current are at a maximum
C)base current is at maximum
D)collector current is at maximum

Question 15

Figure 1
Refer to Figure 1. If VCC is increased to 18 V, IB will

A)decrease
B)increase
C)not change

Question 16

Figure 4
Refer to Figure 4. Assume RB = 22 k▲. The collector current will be approximately

A)5 mA
B)20 mA
C)10 mA
D)27 mA

Question 17

The symbol hFE means the same as

A)aDC
B)fiDC
C)Av
D)PD(max)

Question 18

Figure 4
Refer to Figure 4. The largest base resistor that will still saturate the transistor is approximately

A)33 k▲
B)400 k▲
C)330 k▲
D)40 k▲

Question 19

Typical values of aDC are from

A)20 to 200
B)0.95 to 0.99
C)800 to 1000
D)1.00 to 10

Question 20

The light sensitive region of a photo transistor is the

A)base
B)substrate
C)emitter
D)collector

Question 21

Figure 1
Refer to Figure 1. Assume fiDC = 200. The expected value of IB is

A)200 µA
B)161 µA
C)80 µA
D)182 µA

Question 22

Figure 3 The transistor has the following ratings: P_D(max)= 650 mW, V_CE(max)= 40 V, and I_C(max)= 200 mA.
Refer to Fig 3. Assume VCC is lowered to 15 V. The transistor is

A)saturated
B)in the linear range
C)cutoff

Question 23

When a BJT is conducting, the collector current is identical to the emitter current.

Question 24

hFE varies with

A)temperature
B)collector current
C)both A and B
D)none of the above

Question 25

The base region of a BJT is heavily doped and wide compared to the other two regions.

Question 26

Figure 3 The transistor has the following ratings: P_D(max)= 650 mW, V_CE(max)= 40 V, and I_C(max)= 200 mA.
Refer to Figure 3. The maximum value that VCC can be adjusted to without exceeding the V_CE(max)rating is (ignore other max ratings).

A)60 V
B)45 V
C)50 V
D)40 V

Question 27

The fiDC for a BJT is the ratio of collector current to emitter current.

Question 28

Assume a transistor has a maximum power rating of 1 W and VCE = 5 V. If IC = 120 mA, the power rating is not exceeded.

Question 29

Figure 1
Refer to Figure 1. Assume fiDC = 200. The value of VCE is approximately

A)12.4 V
B)9.2 V
C)7.5 V
D)5.8 V

Question 30

If a BJT is saturated,

A)VCE is approximately 1/2 VCC
B)VCE is approximately equal to VCC
C)V_CE is near zero
D)none of the above

Question 31

In switching circuits, a transistor operates between

A)active region and breakdown
B)cutoff and active region
C)cutoff and saturation
D)none of the above

Question 32

Figure 3 The transistor has the following ratings: P_D(max)= 650 mW, V_CE(max)= 40 V, and I_C(max)= 200 mA.
Refer to Figure 3. If VCC is set to 48 V, PD(max)is exceeded by

A)80 mW
B)55 mW
C)110 mW
D)310 mW

Question 33

A saturated BJT has maximum collector current.

Question 34

The metal mounting tab or case of a power transistor is connected to the

A)base
B)emitter
C)substrate
D)collector

Question 35

ICEO is

A)collector current when the transistor is cutoff
B)collector current when the transistor is saturated
C)collector current when the transistor is on
D)base current when the transistor is saturated

Question 36

Photo transistors have the greatest sensitivity to blue light.

Question 37

The value of fiDC is the ratio of

A)collector current to base current
B)collector current to emitter current
C)emitter current to base current
D)none of the above

Question 38

Figure 7
Refer to Figure 7. Assume a single problem accounts for the readings. From the readings, you can conclude that

A)RB is open
B)the base- collector junction is open
C)the base- emitter junction is open
D)R_C is shorted

Question 39

Figure 4
Refer to Figure 4. If you wanted to change the transistor to a pnp type, you need to

A)increase the base resistor
B)increase the collector resistor
C)change both dc sources to negative supplies
D)all of the above

Question 40

The voltage gain of a BJT amplifier is directly proportional to the internal ac emitter resistance.