Electronics Devices Objective Type Questions: Part-6

Electronics Devices Objective Type Questions

[1] A Zener diode is used for

a) Voltage Regulation

b) Rectification

c) Noise Suppression

d) Blocking A.C

Ans: Voltage Regulation

[2] An SCR is a device having

a) Three layers with four junctions

b) Three layers with two junctions

c) Four layers with three junctions

d) Two layers with three junctions

Ans: Four layers with three junctions

[3] An amplifier has a gain of 10,000 expressed in decibels the gain is

a) 10

b) 40

c) 80

d) 100

Ans: 80

[4] An emitter follows has

a) High input impedance and high output impedance.

b) High input impedance and low output impedance.

c) Low input impedance and high output impedance.

d) Low input impedance and low output impedance.

Ans:High input impedance and low output impedance.

[5] Semi-conductor diode time constant is equal to

a) The value of majority carrier life time

b) The life time of minority carrier

c) The diffusion capacitance time constant

d) Zero

Ans: The value of majority carrier life time

[6] To prepare a P type semiconducting material the impurities to be added to silicon are

a) Boron, Gallium

b) Arsenic, Antimony

c) Gallium, Phosphorous

d) Gallium, Arsenic

Ans:Boron, Gallium

[7] FET is a good signal chopper because

a) It exhibits no offset voltage at zero drain current

b) It occupies less space in integrated form

c) It is less noisy

d) It has got high input impedance

Ans: It exhibits no offset voltage at zero drain current

[8] In Bipolar Junction transistors, the type of configuration which will give both voltage gain and current gain is

a) CC

b) CB

c) CE

d) None

Ans: CE

[9] To increase the input resistance and decrease the output resistance in negative feedback, the type used is

a) Voltage Shunt

b) Current Series

c) Voltage Series

d) Current Shunt 

Ans: Voltage Series

[10] A series capacitance used in a filter circuit represents

a) Low-Pass

b) Band-Pass

c) High-Pass

d) None

Ans: High-Pass

[11] An ideal power supply is characterized by

a) Very large output resistance

b) Very small output resistance

c) Zero internal resistance

d) Infinite internal resistance

Ans: C

[12] An ideal diode should have

a) Zero resistance in the forward bias as well as reverse bias

b) Zero resistance in the forward bias and an infinitely large resistance in reverse bias

c) Infinitely large resistance in reverse bias

d) Infinitely large resistance in forward as well as reverse bias

Ans: B

[13] One coulomb-per-second is equal to one:

a) Watt

b) Joule

c) Volt

d) Ampere

Ans:D

[14] Which of the following is one of the functions performed by a diode?

a) Filter

b) Amplifier

c) Rectifier

d) Inverter

Ans: C

[15] What is the �power factor�?

a) Ratio of true power to apparent power

b) Peak power times 0.707

c) Sin of the phase difference between E and I

d) Cos of the phase angle between true power and apparent power

Ans:A

Solution Hint:

[1] General purpose diode is used for rectification, whereas zener diode is for voltage regulation
[3] Power gain = 10000
Gain in dB = 10log(10000) = 40dB
Voltage gain = 10000
Gain in dB = 20log(10000) = 80dB 

[4] In the Emitter follower circuit, the input side (base-collector terminals) is reverse biased, ie, High input impedance and the Output side (emitter-collector terminals) is forward biased ie, low output impedance

[11] Ideal power supply should not dissipate heat ( ie, internal resistance should be near to zero)

[12] Ideal diode is nothing but ideal DC switch( zero resistance while turned-on and infinity resistance while turned-off)

[13] Flow of charges (unit = coulomb) is known as current(unit = ampere). 

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Electron Devices Objective Type Questions with Answers: part -5

Electron Devices Objective Type Questions

1.When a piece of copper and another of germanium are cooled from room temperature to 800 K then the resistance of -

a) Each of them increases

b) Each of them decreases

c) Copper increases and germanium decreases

d) Copper decreases and germanium increases

Ans: D

2.When a sample of germanium and silicon having same impurity density are kept at room temperature then?

a) Both will have equal value of resistivity

b) Both will have equal value negative resistivity

c) Resistivity of germanium will be higher than that of silicon

d) Resistivity of silicon will be higher than that of germanium

Ans:D

3.When an RC driving point impedance function has zeros at s= -2 and s=-5 then the admissible poles for the function would be?

a) s = 0; s = -6

b) s = 0; s = -3

c) s = 0; s = -1

d) s = -3; s = -4

Ans:B

4.A transistor has CE parameter as hie = 10kW, hre=20 x 10-4 , hse = 100, hoe = 25 ms. The hib for this transistor will be-

a) 100 W

b) 99.01 W

c) 5m W

d) 101kW

Ans:B

5.Which one of the following conditions for Z parameters would hold for a two port network containing linear bilateral passive circuit elements?

a) Z11 = Z22

b) Z12Z21 = Z11Z22

c) Z11Z12 = Z22Z21

d) Z12 = Z21

Ans: D

6.A transistor is in active region when-

a) IB =  �IC

b) IC= �IB

c) IC=IE

d) IC=IB

Ans:B

7.In a JFET gates are always?

a) Forward biased

b) Reverse biased

c) Unbiased

d) None

Ans: C

8.In schotty barrier diode current flows because of?

a) Majority carriers

b) Minority carriers

c) Majority and minority carriers

d) None

Ans:B

9.The early voltage of a BJT is VA = 75V. The minimum required collector current, such that the output resistance is at least r0 = 200kO, is 

(a) 1.67mA

(b) 5mA

(c) 0.375mA

(d) 0.75mA

Ans: C

10.TVS diode is used for

 (a) Voltage protection
 (b) Current protection
 (c) ESD protection
 (d) None of the above

Ans: A

[11] The amplifier is which current is proportional to the signal voltage, independent of source load resistance is called

a) Current Amplifier

b) Voltage Amplifier

c) Transresistance amplifier

d) Transconductance amplifier

Ans: C

[12] Alternatively the characteristic impedance is called
a) Surge Impedance
b) Match Impedance
c) Alternative Impedance
d) Reflected Impedance

Ans: A

[13] In an RL circuit after a very long time of application of step voltage the inductance L is represented in its equivalent circuit as Incorrect!

a) Open Circuit
b) Short Circuit
c) L / 2
d) 2L

Ans: B

[14] By passing a triangular wave through a differentiating circuit the output wave shape is

a) Spikes
b) Squarewave
c) Sawtooth
d) Sinewave

Ans: A

[15] Clipper circuits are used to obtain any one of the following waveforms

a) Sharper
b) Rectified
c) Fast Rising
d) Smaller Amplitude

Ans: D

Solution Hint:
[1] When the temperature increases, the resistance of conductor(copper) decreases and resistance of semiconductor(germanium) increases
 [7] In the FET, the gate terminal is electrically isolated from the channel. ie, it is always unbiased.
[10] TVS stands for Transient Voltage suppressor. It is used for transient voltage protection. 
[15] The clipper circuit will clip part of the waveform. so it can be used for smaller amplitude of the waveform.

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Electronic Devices Objective Questions with Answers: Part-4

Electronic Devices Objective Questions

[1] For harmonic generation the amplifier used is
a)Audio Amplifier
b)Class-A Amplifier
c)RC Amplifier
d)class-C Turned Amplifier

Ans:D

[2] Zener diodes semiconductors are
a)Lightly Doped
b)Heavily Doped
c)Medium Doped
d)Not at all Doped

Ans: B

[3] In FET amplifiers, input is Incorrect!
a)A current signal
b)A voltage signal
c)Either a current or voltage signal
d)None of these

Ans: B

[4] H-parameters of a transistor
a)Are constant
b)Vary with temperature
c)Are dependent upon collector current
d)None of these

Ans:C

[5] In a voltage series feedback
a)Output resistance increases while input resistance decreases
b)Output and input resistances are reduced
c)Output and input resistances are increased
d)Output resistance decreases while input resistance increases

Ans: B

[6]In a saturated transistor
a)B-E junction is forward biased with C-B junction is reverse biased
b)Both the junctions are forward biased
c)B-E junction is reverse biased with C-B junction is forward biased
d)Both the junctions are reverse biased

Ans: B

[7]For an ideal noise free amplifier, the noise figure is
a)Zero
b)Zero dB
c)Infinity
d)1 dB

Ans: B

[8]When a junction is formed between a metal and a semiconductor, the depletion layer is
a)More on the side of the metal
b)Equal on both sides
c)Less on the side of the metal
d)Less on semiconductor side

Ans: C

[9] The impurity commonly used for realizing the base region of a silicon NPN transistor is ______
A) Gallium
B) Indium
C) Boron
D) Phosphorus

Ans: C

[10] A MOS capacitor made using P-type substrate is in the accumulation mode. The dominant charge in the channel is due to the presence of 
A) Holes
B) Electrons
C) Positively charged ions
D) Negatively charged ions

Ans: B

[11] A Zener diode works on the principle of ______
A) Tunneling of charge carriers across the junction
B) Thermionic emission
C) Diffusion of charge carriers across the junction
D) Hopping of charge carriers across the junction

Ans: A

[12] A BJT is said to be operating in the saturation region if______
A) Both the junctions are reverse biased
B) Base-emitter junction is reverse biased & base-collector junction is forward biased
C) Base-emitter junction is forward biased & base-collector junction is reverse biased
D) Both the junctions are forward biased

Ans: D

[13] To obtain very high input & output impedances in a feedback amplifier, the topology used is
A) Voltage-Series
B) Current-Series
C) Voltage-Shunt
D) Current-Shunt

Ans: C

[14] Cut off frequency of a bipolar transistor ____
A) Increase with the increase in base width
B) Increase with the increase in emitter width
C) Increase with the increase in the collector width
D) Increase with the decrease in the base width

Ans: D

[15] Negative feedback in amplifiers
A) Improves the signal to noise ratio at the input
B) Improves the signal to noise ratio at the output
C) Does not affect the signal to noise ratio at the output
D) Does not affect the signal to noise ratio at the input

Ans: B

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Electronic Devices: Part-3 Objective Questions

[1] In order for a BJT to conduct under the conditions of no signal input, the bias must be

(a) In the reverse direction at the E-B junction, sufficient to cause forward breakover.

(b) In the reverse direction at the E-B junction, but not sufficient to cause avalanche effect.

(c) Such that the application of a signal would cause the transistor to go into a state of cutoff.

(d) Such that the application of a signal would cause the transistor to go into a state of saturation.

(e) Such that the application of a signal would cause the transistor to become nonlinear.

Answer: A
[2] The high input impedance of a MOSFET makes this type of device ideal for use in

(a) Weak-signal amplifiers

(b) High-power oscillators

(c) High-current rectifiers

(d) Antenna tuning networks

(e) Graphic equalizers

Answer: A
[3] The drain of a JFET is the analog of the

(a) Plate of a vacuum tube

(b) Emitter of a BJT

(c) Cathode of diode

(d) Positive electrode in a solar cell

(e) Substrate of a MOSFET

Answer: A
[4] One of the technical limitations of capacitive proximity sensors is the fact that they

(a) Are not very sensitive to objects that are poor electrical conductors.

(b) Are insensitive to objects that reflect light.

(c) Are insensitive to metallic objects.

(d) Cannot be used with oscillators

(e) Require extreme voltages in order to function properly

Answer: A
[5] The power factor in an ac circuit is defined as

(a) The actual power divided by the maximum power the circuit can handle.

(b) The ratio of the real power to the imaginary power.

(c) The ratio of the apparent power to the true power.

(d) The ratio of the true power to the apparent power.

(e) The ratio of the imaginary power to the apparent power.

Answer: D
[6] The amount of current that a silicon photodiode can deliver in direct sunlight depends on

(a) The forward breakover voltage.

(b) The thickness of the substrate.

(c) The surface area of the P-N junction.

(d) The applied voltage.

(e) The reverse bias.

Answer: C
[7] In an amplifier that employs a P-Channel JFET, the device can usually be replaced with an N-channel JFET having similar specifications, provided that

(a) All the resistors are reversed in polarity for the circuit in question

(b) The power supply polarity is reversed for the circuit in question

(c) The drain, rather than the source, is placed at signal ground

(d) The output is taken from the source, rather than from the drain.

Answer: B
[8] Secondary breakdown occurs in

(a) MOSFET but not in BJT

(b) Both MOSFET and BJT

(c) BJT but not in MOSFET

(d) None of these

Answer: C
[9] In a transistor

(a)  � =  a/ (a +1)

(b)  � =  a/ (1- a)

(c)  a =  �/ (�-1)

(d)  a = (�+1)/�

Ans:B

Answer: C

[10] The interbase resistance of a UJT is

(a) Less than forward biased PN diode

(b) Higher than a FET

(c) Of the order of 1K an less

(d) In the range of 5K to 10K

Answer: D

[11] The VI characteristics of emitter of a UJT is

(a) Similar to CE with a linear and saturation region

(b) similar to FET with a linear and saturation region

(c) Similar to tunnel diode in some respects

(d) Linear between the peak point and vally point

Answer: C

[12] An UJT used for triggering as SCR has the supply voltage VBB = 25V. The intrinsic stand off ratio n = 0.75. The UJT will conduct when the bias voltage VE is

(a)  25V

(b)  >=18.75V

(c)  33.3V

(d)  >=19.35V

Answer: D

[13] The Oscillator which is not dependent on phase shift is

(a) Wien Bridge

(b) Clapp

(c) Relaxation

(d) Crystal

Answer: C

[14] For an UJT to function, the load line must extend

(a) from saturation region to ohmic region

(b) from saturation to peak value of emitter voltage

(c) from valley point to peak point

(d) within valley and peak points in the negative resistance region

Answer: D

Solution Hint:

[12] VE  = ?.VBB + 0.6   =0.75 x 25 +0.6  =19.35

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ELECTRONIC DEVICES: Part-2 Solved Objective Questions

Objective Questions From Electronic Devices:

[1] In forward mode npn BJT, if the voltage Vcc is increased then the collector current will increase
A. Due to ohm's law, higher Vcc causes higher current
B. Due to base width decrease less carrier recombine in the base region
C. As the gradient of the minority carriers in the base region becomes steeper
D. Due to both the B and C

Ans: D

[2] The barrier voltage present in a junction diode is the effect of
A. The P side and N side of the junction forming a battery
B. The emf required to move the holes fast enough to have the mobility equal to that of the electrons
C. The recombination of charge carriers across the junction leaving behind the opposite charged ions
D. The voltage needed to make the semiconductor material behave as a conductor

Ans: C

[3] Compare to BJT the FET has

A. High input impedance
B. High gain bandwidth product
C. Better current controlled behaviour
D. High noise immunity

Ans: A

[4] An intrinsic semiconductor at absolute zero temperature

A. Has a large number of holes
B. Behaves like an insulator
C. Behaves like a metallic conductor
D. Has few holes and same number of electrons

Ans: A

[5] For the operation of a depletion type N-MOSFET, the gate voltage has to be
A. Low positive
B. High positive
C. High negative
D. Zero

Ans:D

[6] An emitter follower has high input impedance because
A. Large emitter resistance is used
B. Large biasing resistance is used
C. There is negative feedback in the base emitter circuit
D. The emitter base junction is highly reverse biased

Ans: C

[7] In a differential amplifier an ideal CMRR is
A. Infinity
B. Zero
C. -1
D. +1

Ans: A

[8] In a PNP circuit, the collector
A. Has a arrow pointing inward
B. Is positive with respect to the emitter
C. Is biased at a small fraction of the base bias
D. Is negative with respect to the emitter

Ans:D

[9] A PNP transistor can be replaced with an NPN device and the circuit will do the same thing, provided that
A. The power supply or battery polarity is reversed
B. The collector and emitter leads are interchanged
C. The arrow is pointing inward
D. A PNP transistor can never be replaced with NPN transistor

Ans: A

[10] A BJT has 

A. Three PN junctions
B. Three semiconductor layers
C. Two N type layers around a P type layer
D. A low avalanche voltage

Ans: B

[11] The band gap of silicon at room temperature is________
A) 1.3 eV
B) 0.7 eV
C) 1.1 eV
D) 1.4 eV

Ans: C

[12] The primary reason for the widespread use of Silicon in semiconductor device technology is 
A) Abundance of silicon on the surface of the earth
B) Larger bandgap of silicon in comparison to germanium
C) Favorable properties of silicon-dioxide (SiO2)
D) Lower melting Point

Ans: C

[13] The cascade amplifier is a multistage configuration of 
A) CC-CB
B) CE-CB
C) CB-CC
D) CE-CC

Ans: B

[14] In a multi-stage RC coupled amplifier the coupling capacitor______________
A) Limits the low frequency response
B) Limits the high frequency response
C) Does not affect the frequency response
D) Block the DC component without affecting the frequency response

Ans: A

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