# 50 top questions for exam || MCQ transistors || BJT

Answers indicated green with hints if required.

Transistors || BJT

1. Which transistor region is very thin and lightly doped?

A) the emitter region

B) the collector region

C) the another region

D) the base region

2. In a transistor which is the largest of all doped regions

A) the emitter region

B) the collector region

C) the gate region

D) the base region

3. which region in a transistor is most heavily doped

A) the emitter region

B) the collector region

C) the gate region

D) the base region

4. Emitter bias with two power supplies provides a

A) very unstable Q point

B) very stable Q point

C) large base voltage

D) none of the above

5. For a transistor to function as an amplifier

A) both the EB and CB junction must be forward biased

B) both the EB and CB junction must be reverse biased

C) the EB junction must be forward bias and the CB junction must be reverse biased

D) the CB junction must be forward bias and the EB junction must be reverse biased

6. For a typical transistor which two currents and nearly the same

A) base current and emitter current

B) base current and collector current

C) collector current and emitter current

D) none of the above

7. The alpha dc of a transistor equals

A) collector current divided by emitter current

B) base current divided by collector current

C) emitter current divide by collector current

D) collector current divide by base current

8. When transistor is in saturation,

A) Vce =Vcc

B) Ic =0A

C) Vce =0V

D) Vce =1/2 Vcc

9. A transistor has the base current equal to 20 milliampere and collector current equal to 4.98 ampere ,Calculate emitter current.

A)10A

B) 20A

C) 5A

D) 22.5mA

Hint : (emitter current equal to base current + collector current)

10. A transistor has emitter current equal to 15 ampere and base current equal to 60 micro ampere ,calculate alpha DC.

A) 0.996

B) 200

C) 199

D) 5mA

Hint : alpha dc equal to collector current divide by emitter current, also collector current equal to emitter current – base current

11. Transistor has collector current 10 mA base current 50 microampere ,calculate beta DC.

A) 0.996

B) 200

C) 199

D) 11.25 microampere

Hint : beta DC equal to collector current divide by base current

12. A transistor has alpha DC equal to 0.995, calculate beta DC

A) 0.99

B) 0.97

C) 200

D) 199

Hint : beta DC equal to alpha DC divide by (1 – alpha DC)

13. A transistor is made up of three regions emitter, base and collector.

A) base is a very thin layer

B) emitter is lightly doped region

C) collector is the moderate in size

D) all are true

14. In what operating region does the collector of a transistor act like a current source.

A) active region

B) cutoff region

C) saturation region

E) the breakdown region

15. Which of the following biasing techniques produce the most unstable Q point.

A) voltage divider bias

B) emitter bias

C) collector bias

D) Base bias

16. When the collector current in a transistor is zero ,the transistor is

A) cut off

B) saturated

C) operating in the breakdown region

D) either b or c

17. For a transistor operating in the active region,

A) collector current equal to beta DC x base current

B) Vcc has little or no effect on the value of collector current

C) collector current is controlled by Vcc

D) both a and b

18. In a transistor amplifier ,what happens to the collector voltage ,when the collector current increases?

A) collector voltage increases

B) collector voltage stays the same

C) collector voltage decreases

D) this is impossible to determine

19. On the symbol of PNP transistor

A) arrow points out on the emitter lead

B) arrow points out on the collector lead

C) arrow points in on the base lead

D) arrow points in on the emitter lead

20. A BJT has

A) only one PN junction

B) three PN junctions

C) no PN junction

D) two PN junctions

21. In a transistor which current is the largest

A) collector current

B) base current

C) emitter current

D) diode current

22. In a transistor the line to which an arrowhead is marked is called

A) emitter

B) collector

C) base

D) gate

23. If a emitter current in a transistor is 2mA , the collector current will be nearly

A) 2mA

B) 4mA

C) 0.01mA

D) 8mA

24. In a transistor with normal biasing, the

A) emitter junction has high and collector junction has low resistance

B) emitter junction has low and collector junction has high resistance

C) both emitter and collector junctions have low resistance

D) both emitter and collector junctions have high resistance

25. The most commonly used transistor circuit arrangement is

A) common base

B) common emitter

C) common collector

D) none of these

26. For transistor action,

A) the base region must be very thin and lightly doped

B) the emitter junction should be forward biased and collector junction should be reverse baised

C) the emitter should be heavily doped so that it can supply the required amount of majority carriers

D) all of these

27. The magnitude of leakage current in collector base junction with emitter open is

A) depends largely upon the emitter doping

depends largely upon the emitter base junction bias potential

C) increases with the increase in temperature

D) is generally greater in silicon than germanium transistor

28. The silicon transistors are more widely used than germanium transistors because

A) they have smaller leakage current

B) they have smaller depletion layers

C) they have better ability to dissipate heat

D) they have larger current carrying capacity

29. A transistor when connected in CE mode has

A) a low input resistance and low output resistance

B) a high input resistance and high output resistance

C)high input resistance and low output resistance

D) a medium input resistance and high output resistance

30. A CE amplifier circuits are preferred over CB amplifier circuits because they have

A) lower amplification factor

B) larger amplification factor

C) high input resistance and low output resistance

D) none of these

31. The main current crossing the collector junction in a normally biased NPN transistor is

A) diffusion current

B) drift current

C) hole current

D) equal to the base current

32. The emitter region in the PNP junction transistor is more heavily doped then the base region so that

A) the flow across the base region will be mainly because of electrons

B) the flow across the base region will be mainly because of holes

C) recombination will be increased in the base region

D) base current will be high

33. For a given emitter current, the collector current will be higher if

A) the recombination rate in the base region were decreased

B) the emitter region were more lightly doped

C) the minority carrier mobility in the base region were reduced

D) the base region were made wider

34. A small increase in the collector reverse bias will cause

A) a large increase in emitter current

B) a large increase in collector current

C) a large decrease in collector current

D) very small change in collector reverse saturation current

35. The input and output signals of a common emitter amplifier are

A) always equal

B) out of phase

C) always negative

D) in phase

36. A transistor is connected in common base configuration has

A) a low input resistance and high output resistance

B) high input resistance and low output resistance

C) a low input resistance and low output resistance

D) high input resistance and high output resistance

37. A transistor is said to be in quiescent state when

A) no signal is applied to the input

B) it is unbiased

C) no currents are flowing

D) emitter junction bias is just equal to collector junction bias

38. The voltage gain of a transistor connected in common collector arrangement is

A) equal to 1

B) more than 10

C) more than 100

D) less than 1

39.The phase difference between the input and the output voltage of transistor in common collector configuration is

A) zero degree

B) 180 degree

C) 90 degree

D) 270 degree

40. BC 147 transistor indicates that it is made of …

A) germanium

B) silicon

C) carbon

D) none of these

41.IC = β IB + ………..

A) ICBO

B) IC

C) ICEO

D) αIE

42.ICEO = (………) ICBO

A) β

B) 1 + α

C) 1 + β

D) none of the above

43. Heat sink used with the transistor to

A) increase the forward current

B) decrease the forward current

C) compensate for excessive doping

D) prevent excessive temperature rise