Untitled Document

Question Bank No: 1

1. Which of the following logic gate is a Universal gate

a)		OR
b)		NOT
c)		0.01 mA
d)		10 mA

2. The expression y in the following circuit is
solid-semicon-Q19

a)		ABCD
b)		B+ACD
c)		AB+CD
d)		A+B+C+D

3. In a semi conducting material the mobilities of electrons and holes are $M_{e}$ and $M_{h}$

a)		$M_{e} > M_{h}$
b)		$M_{e} < M_{h}$
c)		$M_{e} = M_{h}$
d)		$M_{e} < {0 M}_{h} > 0$

4. In a common base amplifier, the phase difference between the input signal voltage and output voltage is

a)		$π / 2$
b)		0
c)		$π$
d)		$π / 4$

5. In an n-p-n transister the collector current is 24 mA if 80% of electrons reach collector, its base current in mA is

a)		36
b)		26
c)		16
d)		6

6. A semi conductor has an electron concentration of 8 $\times 10^{13} / m^{3}$ and hole concentration of 5.5 $\times 10^{12} / m^{- 3}$ .The semi conductor is

a)		n-type
b)		p-type
c)		intrinsic Semiconductor
d)		P.N.junction

7. Which one is forward biased

a)
b)
c)
d)		none of these

8. Correct relation for triode is

a)		$μ = g_{m} \times r_{p}$
b)		$μ = g_{m} / r_{p}$
c)		$μ = 2 g_{m} \times r_{p}$
d)		none of these

9. Biaxial crystal among the following is

a)		Calcite
b)		Quartz
c)		Selenite
d)		Tourmaline

10. For a common base amplifier, the values of resistance gain and voltage gain are 3000 and 2500 respectively.The power gain of the amplifier will be

a)		1341.6
b)		2083.3
c)		1712.5
d)		2683.2

11. A n-p-n transistar circuit has $\propto$ = 0.985.If $I_{c} = 2 mA . Then the value of I_{b} is$

a)		0.03mA
b)		0.003mA
c)		0.66mA
d)		0.015mA

12. What is the name of the gate obtained by the combination from fig:
solid-semicon-Q9

a)		NAND
b)		NOR
c)		NOT
d)		XOR

13. Radio waves of constant amplitude can be generated with

a)		FET
b)		Filtter
c)		Rectifier
d)		Oscillater

14. A transistar has a base current of 1mA and emitter current 90 mA. The Collector current will be

a)		90 mA
b)		1mA
c)		80 mA
d)		91 mA

15. PN junction is

a)		Ohmic resistance
b)		Non- ohmic resistance
c)		Negative resistance
d)		Positive resistance

16. If the forward voltage in a Semiconductor diode is changed from 0.5 V to 0.7 V .Then the forward current changes by 1.0m A.The forward resistance of diode junction will be

a)		100 $Ω$
b)		120 $Ω$
c)		200 $Ω$
d)		240 $Ω$

17. The typical ionisation energy of a donor in silicon is

a)		10.0 eV
b)		1.0 eV
c)		0.1 eV
d)		0.001 eV

18. If lattice parameter for a crystalline structure is 3.6 , $A^{0}$ Then atomic radius in fcc crystal in $A^{0}$ is

a)		7.20
b)		1.80
c)		1.27
d)		2.90

19. Child's law

a)		$I_{P} = K {V_{P}}^{1 / 2}$
b)		$I_{P} = K {V_{P}}^{3 / 2}$
c)		$I_{P} = K {V_{P}}^{1 / 3}$
d)		$I_{P} = K {V_{P}}^{2 / 3}$

20. Thermionic process does not depend upon

a)		work function
b)		surface area
c)		temperature
d)		melting point

21. A half wave rectifier is used to rectify 50Hz a.c. Number of pulses of rectified signal obtained in one second will be

a)		100
b)		50
c)		25
d)		75

22. Two amplifiers having gains 10 and 20 are cascaded with each other. If a signal of 10 mV is applied at the input, output signal will be

a)		200 mA
b)		100 mA
c)		300m
d)		2 V

23. A charge of 7.89 mA in emitter current produces a charge of 7.8 mA in collector current. Then charge in base current is

a)		7.8 mA
b)		7.89 mA
c)		0.09 mA
d)		0.9 mA

24. Boolean algebra is essentially based on

a)		symbol
b)		logic
c)		numbers
d)		truth

25. The number of donors per unit volume in a PN- junction is $N_{d}$ and the number of acceptor is $N_{a}$ . If the depletion layer has a width $X_{1}$ in the p-side and width $X_{2}$ in the N-side, then

a)		$N_{d} X_{1} = N_{a} X_{2}$
b)		$X_{1} = X_{2}$
c)		$N_{a} X_{1} = N_{d} X_{2}$
d)		$X_{1} . \sqrt{N_{d}} = X_{2} \sqrt{N_{a}}$

26. A change in 100 $μ$ A in the base current in a common emitter NPN-transistor cause a change of 10 mA in collector current. Then the current gain of the transistor will be

a)		125
b)		100
c)		50
d)		75

27. A CE amplifier is designed with a transistor having $α =$ 0.99. Input impedence is 1k $Ω$ and load is 10k $Ω$ . Voltage gain will be

a)		9900
b)		99000
c)		99
d)		990

28. The grid voltage of any triode valve is changed from -1 volt to -3 volt and the mutual conductance is 3 $\times 10^{- 4}$ mho. The change in plate current will be

a)		0.8 mA
b)		0.6 mA
c)		0.4 mA
d)		1 mA

29. Sodium has body centred packing. When the distance between two nearest atoms is 3.7 $\overset{\circ}{A}$ . Then lattice parameter is

a)		3.3 A
b)		4.3 A
c)		4.8 A
d)		4.4 A

30. Following is the relation betwen current and charge I=A $T^{2} e^{- φ_{0} / V}$ then the value of V will be

a)		1 / kT
b)		k / T
c)		kT
d)		VT / k

31. In an insulator, the forbidden energy gap between the valence band conduction band is of the order

a)		1 MeV
b)		1 eV
c)		5 eV
d)		5 MeV

32. Relation between the current gains ( $α$ and $β$ ) od a transistor is

a)		$α = (1 - β) / β$
b)		$α = β / (1 - β)$
c)		$α = β / (1 + β)$
d)		$α = (1 + β) / β$

33. Reverse bias applied to a junction diode

a)		lowers the potential barrier
b)		raises the potential barries
c)		increases the majority carrier current
d)		decreases the majority carrier current

34. In the study of transistor as an amplifier, if $α = I_{c} / I_{e}$ and $β = I_{c} / I_{b}$ where $I_{c}$ , $I_{b}$ and $I_{e}$ are collector, base and emitter currents, then

a)		$α = β + 1$
b)		$α + β = 1$
c)		$\frac{α}{α + 1}$ = $β$
d)		$α = \frac{β}{1 + β}$

35. When we add binary numbers 111 and 111 we get the binary number

a)		222
b)		1000
c)		1110
d)		000

36. Of the following correct arrangement of semiconductors in the order of their increasing energy gap is

a)		Silicon, Germanium, Tellurium
b)		Germanium, Silicon, Tellurium
c)		Tellurium, Germanium, Silicon
d)		Tellurium, Silicon, Germanium

37. Packing fraction of a simple cubic unit cell in cubic crystal is

a)		$π / 8$
b)		$π / 6$
c)		$π \sqrt{3} / 8$
d)		$π / \sqrt{3}$

38. A P-type semiconductor is a

a)		germanium crystal doped with phosphorous
b)		germanium crystal doped with boron
c)		silicon crystal doped with boron
d)		silicon crystal doped with aluminum

39. When the resistance between the P and N sections of junction diode is high, then the diode acts as a

a)		transistor
b)		capacitor
c)		resistor
d)		none of these

40. In common base amplifier, the phase difference between input signal voltage and output voltage is

a)		0
b)		$π$ /4
c)		$π / 2$
d)		$π$

41. IN an P-N-P transistor, the collector current is 10mA. If 90% of the holes reach the collector, then emitter current will be

a)		13 mA
b)		12 mA
c)		11 mA
d)		10 mA

42. The forbidden energy band gap is maximum in

a)		semiconductors
b)		super conductors
c)		insulators
d)		metals

43. Which of the following when used as dopant in silicon produces N-type semiconductor?

a)		As
b)		AI
c)		B
d)		In

44. In an insulator forbidden energy gap between is of the order of

a)		5 eV
b)		1 eV
c)		0.1 eV
d)		0.75 eV

45. For Ge forbiden energy gap in joules is

a)		1.76 $\times 10^{- 19}$
b)		1.12 $\times 10^{- 19}$
c)		1.6 $\times 10^{- 19}$
d)		Zero

46. A transistor is used in the common emitter mode as an amplifier. Then

a)		The base emitter junction is forward biased
b)		The base emitter junction is reverse biased
c)		The input signal is connected in series with the voltage applied to bias the base emitter junction
d)		The input signal is connected in series with the voltage applied to bias the base collector junction

47. When a silicon junction diode is forward biased by applying a voltage of 0.9 V; then current through the diode is 55 mA at $27^{\circ} C$ . Then d.c. resistance of the circuit will be

a)		5.3 ohm
b)		12.8 ohm
c)		16.4 ohm
d)		23.8 ohm

48. How many minimum number of NAND gates are needed to form an AND gate

a)		2
b)		3
c)		4
d)		5

49. At OK, intrinsic semiconductor behaves as

a)		a semiconductor
b)		a perfect insulator
c)		a perfect conductor
d)		a superconductor

50. Electrical conductivities of Ge and Na are $σ_{1}$ and $σ_{2}$ respectively. If both of them are heated then

a)		$σ_{1}$ increases and $σ_{2}$ decreases
b)		$σ_{1}$ decreases and $σ_{2}$ increases
c)		$σ_{1}$ and $σ_{2}$ both increases
d)		$σ_{1}$ and $σ_{2}$ both decreases