1: In an electronic circuit, common reference point is
a. Always the negative battery terminal
b. Always the most positive point
c. Always the most negative point
d. May be any point
2: The word “Ground” means
a. A direct connection to earth through a wire
b. A common connection for all components
c. A short circuit
d. Negative battery terminal
3: For doubling the current in a circuit of constant resistance the applied voltage must be
a. Remains same
b. Halved
c. Doubled
d. Quadrupled
4: Total current drawn from four 1.5V cells connected in series is 1A. Each cell supplies …….. amperes current
a. 1A
b. 0.25A
c. 1.5A
d. 4A
5: Electron-volt is unit of
a. Voltage
b. Current
c. Energy
d. Power
6: Two resistors are said to be connected in series when
a. Both carry same amount of current
b. Total current equals the sum of branch currents
c. Sum of IR drops equals battery emf
d. They provide only one path for the current flow
7: The storage element of a DRAM is a
a. Resistor
b. Transistor
c. Capacitor
d. Diode
8: ADDRESS-BURST is a feature of
a. Synchronous SRAM
b. Asynchronous SRAM
c. Fast page mode SRAM
d. synchronous DRAM
9: Every known element has
a. The same type of atoms
b. A unique type of atom
c. The same number of atoms
d. Several different types of atom
10: An atom consist of
a. One nucleus and only one electron
b. One nucleus and one or more electrons
c. Protons, electrons, and neutrons
d. b or c
11: The nucleus of an atom is made up to
a. Proton and neutrons
b. Electrons and protons
c. Electrons
d. Electrons and protons
12: The atomic number of silicon is
a. 8
b. 14
c. 4
d. 2
13: The atomic number of germanium is
a. 32
b. 4
c. 2
d. 8
14: The valence shell in a silicon atom has the number designation of
a. 1
b. 0
c. 3
d. 2
15: Valence electrons are
a. In the closet orbit to the nucleus
b. In various orbits around the nucleus
c. In the most distant orbit from the nucleus
d. Not associated with a particular atom
16: A positive ion is formed when
a. There are more holes than electrons in the outer orbit
b. Two atoms bond together
c. A valence electron breaks away from the atom
d. An atom gains extra valence electron
17: The most widely used semi-conductive material in electronic device is
a. Silicon
b. Carbon
c. Germanium
d. Copper
18: The energy band in which free electrons exist is the
a. 1st band
b. Conduction band
c. 2nd band
d. Valence band
19: Electron-holes pairs are produced by
a. Ionization
b. Thermal energy
c. Recombination
d. Doping
20: Recombination is when
a. A crystal is formed
b. A positive and a negative ion bond together
c. An electron falls into a hole
d. A valence electron becomes a conduction electron
21: In a semiconductor crystal, the atoms are held together by
a. Forces of attraction
b. The interaction of valence electrons
c. Covalent bonds
d. a, b, c
22: Each atom in a silicon crystal has
a. No valence electrons because all are shared with others atoms
b. Eight valence electrons because all are with other atoms
c. Four valence electrons
d. Four conduction electrons
23. The current in a semiconductor is produced by
a. Holes only
b. Electrons only
c. Both electrons & holes
d. Negative ions
24. In an intrinsic semiconductor
a. There are no free electrons
b. The free electrons are thermally produced
c. There are as many electrons as there are holes
d. b and d
25: The difference between an insulator and a semiconductor is
a. A wider energy gap between the valence band and the conduction band
b. The number of free electrons
c. The atomic structure
d. a, b & c
26. The process of adding an impurity to an intrinsic semiconductor is called
a. Atomic modification
b. Doping
c. Recombination
d. Ionization
27: A trivalent impurity is added to silicon to create
a. Germanium
b. An N-type semiconductor
c. A depletion region
d. A p-type semiconductor
28: The purpose of a pentavalent impurity is to
a. Increase the number of free electrons
b. Create minority carriers
c. Reduce the conductivity of silicon
d. Increase the number of holes
29: The majority carriers in an N-type semiconductor are
a. Holes
b. Conduction electrons
c. Valence electron
d. Protons
30: Holes in an n-type semiconductor are
a. Minority carriers that are thermally produced
b. Majority carriers that are thermally produced
c. Minority carriers that are produced by doping
d. Majority carriers that are produced by doping
31: A P-N junction is formed by
a. Ionization
b. The boundary of a p-type and an n-type material
c. The recombination of electrons and holes
d. The collision of a proton and a neutron
32: The depletion region is created by
a. Ionization
b. Diffusion
c. Recombination
d. a, b & c
33: The depletion region is consist of
a. Nothing but minority carriers
b. Positive and negative ions
c. No majority carriers
d. b & c
34: The term bias means
a. A dc voltage is applied to control the operation of a device
b. Neither a, b nor c
c. The ratio of majority carriers to minority carriers
d. The amount of current across a diode
35: To forward-bias a diode
a. An external voltage is applied that is positive at the anode and negative at the cathode
b. An external voltage applied that is negative at the anode and positive at the cathode
c. An external voltage is applied that is positive at the p region and negative at the n region
d. a & c
36: When diode is forward-biased
a. The only current is hole current
b. The only current is produced by majority carriers
c. The current is produced by both holes and electrons
d. The only current is electron current
37: Although current is blocked in reverse bias
a. There is some current due to majority carriers
b. There is very small current due to minority carriers
c. There is an avalanche current
38: For a silicon diode, the value of the forward-bias voltage typically
a. Must be greater than 0.3 V
b. Depends on the width of the depletion region
c. Depends on the concentration of majority carriers
d. Must be greater than 0.7 V
39: When forward-biased, a diode
a. Block current
b. Has a high resistance
c. Conducts current
d. Drops a large voltage
40: When a voltmeter is placed across a forward-biased diode, it will read a voltage approximately equal to
a. The diode barrier potential
b. The bias battery voltage
c. The total circuit voltage
d. 0V
41: A silicon diode is in series with 1.0 k℧ resistor and a 5V battery. If the anode is connected to the positive battery terminal, the cathode voltage with respect to the negative battery terminal is
a. 0.7V
b. 5.7V
c. 0.3V
d. 4.3V
42: The positive lead of an ohmmeter is connected to the anode of a diode and the negative lead is connected to the cathode. The diode is
a. Reverse-biased
b. Forward-biased
c. Open
d. Faulty
43: The average value of a half-wave rectified voltage with a peak value of 200V is
a. 127.3V
b. 141V
c. 0V
d. 63.7V
44: When a 60Hz sinusoidal voltage is applied to the input of a half-wave rectifier, the output frequency is
a. 60 Hz
b. 120 Hz
c. 0 Hz
d. 30 Hz
45: The peak value of the input to a half-wave rectifier is 10V. The approximate peak value of the output is
a.10.7V
b. 9.3V
c. 10V
d. 80V
46: For the circuit in Question in Question 3, the diode must be able to withstand a reverse voltage of
a. 5V
b. 10V
c. 20V
d. 3.18 V
47: The average value of a full-wave rectified voltage with a peak value of 75V is
a. 37.5 V
b. 23.9V
c. 53V
d. 47.8V
48: When a 60Hz sinusoidal voltage is applied to the input of a full-wave rectifier, the output frequency is
a. 60Hz
b. 120Hz
c. 240
d. 0Hz
49: The total secondary voltage in a center-tapped full-wave rectifier is 125rms. Neglecting the diode drop, the -output is
a. 117V
b. 120V
c. 62.5
d. 125V
50: When the peak output voltage is 100V, the PIV for each diode in a center-tapped full-wave rectifier is (neglecting the diode drop)
a. 100V
b. 141V
c. 40V
d. 200V
51: When the rms-output voltage of a bridge full wave rectifier is 20V, the peak inverse voltage across the diodes is (neglecting the diode drop)
a. 28.3V
b. 20V
c. 40V
d. 56.6V
52: A certain power supply filter produces an output with a ripple of 100 mV peak-to-peak and a dc value of 20V. The ripple factor is
a. 0.005
b. 0.05
c. 0.02
d. 0.00005
53: A 60V peak full-wave rectified voltage is applied to a capacitor-input filter. If f=120Hz. RL= 10k℧ and dC=10µF, the ripple voltage is
a. 0.6V
b. 5.0V
c. 6mV
d. 2.88V
54: If the load resistance of a capacitor-filtered full-wave rectifier is reduced, the ripple voltage
a. Is not affected
b. Increases
c. Decreases
d. Has a different frequency
54: Line regulation is determined by
a. Zener current and load current
b. Changes in load resistance and output voltage
c. Load current
d. Changes in output voltage and input voltage
55: Load regulations is determined by
a. Changes in zener current and load current
b. Changes in load current and output voltage
c. Changes in load current and input voltage
d. Changes in load resistance and input voltage
56: A 10V peak-to-peak sinusoidal voltage is applied across a silicon diode and series resistor. The maximum voltage across the diode is
a. 36V
b. 33.9V
c. 21V
d. 23V
57: If the input voltage to a voltage tripler has an rms-value of 12V, the dc output voltage is approximately
a. 36V
b. 33.9V
c. 21V
d. 50.9V
58: If one of the diode in a bridge full-wave rectifier opens, the output is
a. One-fourth the amplitude of the input voltage
b. A half-wave rectified voltage
c. 0V
d, 120Hz
59: If you are checking a full-wave bridge rectifier and observe that the output has a 60Hz ripple
a. The filter capacitor is leaky
b. The transformer secondary is shorted
c. There is an open diode
d. The circuit is working properly
60: The cathode of zener diode in a voltage regulator is normally
a. More negative than the anode
b. More positive than the anode
c. At 40V
d. Grounded
61: If a certain zener diode has a zener voltage of 3.6V, it operates in
a. Avalanche breakdown
b. Zener breakdown
c. Regulated breakdown
d. Forward conduction
62: For a certain 12V zener diode, a 10 mAchange in zener current produces a 0.1V change in zener voltage. The zener impedance for this current ranges is
a. 0.1 ohm
b. 100 ohm
c. 10 ohm
d. 20 ohm
63: A no-load condition means that
a. The load has infinite resistance
b. The load has zero resistance
c. a and c
d. The output terminals are open
64: A varactor diode exhibits
a. A variable capacitance that depends on forward current
b. A variable capacitance that depends on reverse voltage
c. A constant capacitance over a range of reverse voltages
d. A variable resistance that depends on reverse voltage
65: An LED
a. Emits light when forward-biased
b. Emits light when reverse-biased
c. Acts as a variable resistance
d. Senses light when reverse-biased
66: Compared to a visible red LED, an infrared LED
a. Produces light with longer wavelength
b. Produces light when reverse-biased
c. Produces light with shorter wavelengths
d. Produces only one color of light
67: The internal resistance of a photodiode
a. Increase with light intensity when forward-biased
b. Decrease with light intensity when forward-biased
c. Increases with light intensity when reverse-biased
d. Decrease with light intensity when forward-biased
68: A diode that has a negative resistance characteristics is the
a. Tunnel diode
b. Laser diode
c. Schottky diode
d. Hot-carrier diode
69: An infrared LED is optically coupled to a photodiode. When the LED is turned off, the reading on an ammeter is series with the reverse-biased photodiode will
a. Increase
b. Not change
c. fluctuate
d. Decrease
70: In order for a system to function properly, the various types of circuits that make up the system must be
a. Properly biased
b. Properly connected
c. Properly interfaced
d. all of these
71: The three terminals of a bipolar junction transistor are called
a. Input, output, ground
b. P,N,P
c. Base, emitter, collector
d. N,P,N
72: In a P-N-P transistor, the P-region are
a. Base and emitter
b. Base and collector
c. Emitter and collector
73: The maximum value of collector current in a biased transistor is
a. $\beta_{dc}I_B$
b. $I_{C\left(sat\right)}$
c. Greater than $I_E$
d. $I_E-I_B$
74: Ideally, a dc load line is s straight line drawn on the collector characteristics curves between
a. The Q-point and saturation
b. $V_{CE\left(cutoff\right)}\ and \ \ I_{C\left(sat\right)}$
c. The Q-point and cut-off
d. $I_B=0\ \ and \ \ I_B=\frac{I_C}{\beta_{dc}}$
75: If a sinusoidal voltage is applied to the base of a biased npn transistor and the resulting sinusoidal collector voltage is clipped near zero volts, the transistor is
a. Being driven into saturation
b. Being driven into cut off
c. Operating nonlinearly
d. b and c
76: The input resistance at the base of a biased transistor depends mainly on
a. $\beta_{dc}$
b. $\mathbf{\beta_{dc}\ and \ R_E}$
c. $R_B$
d. $R_E$
77: In a certain voltage-divider biased N-P-N transistor, is 2.95V. The dc emitter voltage is approximately
a. 2.95V
b. 2.25V
c. 0.7V
d. 3.65V
78: Voltage-divider bias
a. Can be essentially independent of $\beta_{dc}$
b. Is not widely used
c. Cannot be independent of $\beta_{dc}$
d. Requires fewer components than all the other methods
79: The disadvantage of base bias is that
a. It produces low gain
b. It is very complex
c. It produces high leakage current
d. It is too beta dependent
80: Emitter bias is
a. Essentially independent of $\beta_{dc}$
b. Very dependent of $\beta_{dc}$
c. Provides a stable bias point
d. a and c
81: In an emitter bias circuit, $R_E=2.7\ k\Omega$ and $V_{EE}=15V$ . The emitter current
a. Is 180 mA
b. Is 2.7 mA
c. Is 5.3 mA
d. Cannot be determined
82: Collector-feedback bias is
a. Based on the principle of negative feedback
b. Based on beta multiplication
c. Based on the principle of positive feedback
d. Not very stable
83: In a voltage-divider biased N-P-N transistor, if the upper voltage-divider resistor (the one connected to ) opens,
a. The transistor burns out
b. The transistor goes into saturation
c. The transistor goes into cutoff
d. The supply voltage is too high
84: In a voltage-divider biased N-P-N transistor, if the lower voltage-divider resistor (the one connected to ) opens.
a. The collector current will decrease
b. The transistor may be driven into saturation
c. The transistor is not affected
d. The transistor may be driven into cutoff
85: In a voltage-divider biased P-N-P transistor, there is no base current, but the base voltage is approximately correct. The most likely problem(s) is
a. A bias resistor is open
b. The base-emitter junction is open
c. The emitter resistor is open
d. b and c
86: The emitter of a transistor is generally doped the heaviest because it
a. Has to dissipate maximum power
b. Has to supply the charge carriers
c. Is the first region of the transistor
d. Must possess low resistance
87: For proper working of a transistor in normal circuits
a. EBJ is reverse biased and CBJ forward biased
b. EBJ is forward biased and CBJ forward biased
c. CBJ is reverse biased and EBJ forward biased
d. CBJ is reverse biased and EBJ reverse biased
88: In a properly biased NPN transistor most of the electrons from the emitter
a. Recombine with holes in the base
b. Recombine in the emitter itself
c. Pass through the base to the collector
d. Are stopped by the junction barrier
89: The current amplification factor alpha dc $\mathbf{\alpha_{dc}}$ is given by
a. $\mathbf{\frac{I_C}{I_E}}$
b. $\frac{I_C}{I_B}$
c. $\frac{I_B}{I_E}$
d. $\frac{I_B}{I_C}$
190: The common-emitter forward amplification factor $\beta_{dc}$ is given by
a. $\frac{I_C}{I_E}$
b. $\frac{I_C}{I_B}$
c. $\frac{I_B}{I_E}$
d. $\frac{I_B}{I_C}$
92: The following relationships between $\alpha$ and $\beta$ are correct except
a. $\beta=\frac{\alpha}{1-\alpha}$
b. $\alpha=\frac{\beta}{1-\beta}$
c. $\alpha=\frac{\beta}{1+\beta}$
d. $\mathbf{1-\alpha=\frac{1}{1+\beta}}$
92: The value of total collector current in a CB circuit is
a. $I_C=\alpha I_E$
b. $\mathbf{I_C=\alpha I_E+I_{CO}}$
c. $I_C=\alpha I_E-I_{CO}$
d. $I_C=\beta I_E$
93: In case of bipolar transistor α is
a. Positive and >1
b. Positive and <1
c. Negative and >1
d. Negative and <1
94: When the E/B junction of a transistor is reverse biased , the collector current is
a. Reversed
b. Increases
c. Decreases
d. Stops
95: The EBJ of a given transistor is forward biased and its CBJ reverse biased. If the base current is increased then its
a. $I_C$will decrease
b. $V_{CE}$ will increase
c. $\mathbf{I_C}$ will increase
d. $V_{CC}$ will increase
95: The dc load line of a transistor circuit
a. Has a negative slope
b. Is a curved line
c. Gives graphic relation between $I_C$ and $I_B$
d. Does not contain the Q-point
96: The maximum peak-to-peak output voltage swing is obtained when the Q-point of a circuit is located
a. Near saturation point
b. Near cut-off point
c. At the centre of load line
d. At least on the load line
97: The positive swing of the output signal starts clipping first when Q-point of the circuit moves
a. To the centre of load line
b. Two-third way up the load line
c. Towards the saturation point
d. Towards the cut-off point
98: The improper biasing of a transistor circuit leads to
a. Excessive heat production at collector terminal
b. Distortion in output signal
c. Faulty location of load line
d. Heavy loading of emitter terminal
99: The ac load line of a transistor circuit is steeper than its dc line because
a. It has steeper slope
b. ac signal sees less load resistance
c. $I_C$ is higher
d. Input signal varies in magnitude
100: The universal bias stabilization circuit is the most popular because
a. $I_C$ does not depend on transistor characteristics
b. Its $\beta-sensitivity$ is high
c. Voltage divider is heavily loaded by transistor base
d. $I_C$ equals $I_E$
101: The voltage gain of a well-designed single-stage CB amplifier is essentially determined by ac collector load and
a. Emitter resistor RE
b. ac alpha
c. Input resistance of emitter diode
d. ac beta
102: In a single-stageCBamplifier, a smaller load resistance RL will produce
a. High current gain
b. Low voltage gain
c. Better frequency response
d. Higher power gain
103: The basic reason for using an emitter bypass capacitor in a CE amplifier circuit is to
a. Keep emitter at ac ground
b. Decrease stage voltage gain
c. Prevent excessive degeneration from taking place
d. Bypass low-frequency signal component
104: The voltage gain of an emitter follower is
a. More than its current
b. Less than or equal to unity
c. Greater than or equal to unity
d. Dependent on emitter load
105: The main use of an emitter follower is as
a. Power amplifier
b. Low-input impedance circuit
c. Impedance matching device
d. Follower of base signal
106: The are called hybrid because they are
a. Obtained from different characteristics
b. Mixed with other parameters
c. Apply to circuits contained in a black box
d. Identified by using both open-and-short circuit terminations
107: The smallest of the four of a transistor is
a. $h_i$
b. $h_i$
c. $\boldsymbol{h_o}$
d. $h_f$
108: The typical value of $h_{ie}$ is
a. 1K
b. 25K
c. 50K
d. 100K
109: The CE amplifier is characterized by
a. Low voltage gain
b. Moderate power gain
c. Very high output impedance
d. Signal phase reversal
110: A CC amplifier has the highest
a. Voltage gain
b. Current gain
c. Power gain
d. Output impedance
111: In a class-A amplifier, conduction extends over 360o because Q-point is
a. Located on load line
b. Located near saturation point
c. Centered on load line
d. Located at near cut-off point
112: In a class-A amplifier, worst-case condition occurs with
a. Zero signal input
b. Maximum signal input
c. High load resistance
d. Transformer coupling
113: The output of class-B amplifier is
a. Distortion-free
b. Consists of positive half cycles only
c. Like the output of a full-wave rectifier
d. Comprises short-duration current
214: The maximum overall efficiency of a transformer-coupled class-A amplifier is……….…… percent
a. 78.5
b. 25
c. 50
d. 85
115: A transistor audio amplifier is found to have an overall efficiency of 70%. Most probably, it is a ……….. amplifier
a. Single-stage class C
b. Class-B push-pull
c. Transformer-coupled class-A
d. Direct-coupled class-A
116: A class-B push-pull amplifier has the main advantage of being free from
a. Any circuit imbalances
b. Unwanted noise
c. Even-order harmonic distortion
d. dc magnetic saturation effects
117: Cross-over distortion occurs in…….. amplifiers
a. Push-pull
b. Class-A
c. Class-B
d. Class-AB
118: The maximum overall efficiency of a class-B push-pull amplifier cannot exceed……….…… percent
a. 78.5
b. 25
c. 100
d. 85
119: The main use of class-C amplifier is as
a. An RF-amplifier
b. A stereo-amplifier
c. As distortion generator
d. In communication sound equipment
120: The primary cause of linear distortion in amplifier is
a. Change of gain with frequency
b. Unequal phase-shift in component frequencies
c. Reactances associated with the circuit and active amplifying element
d. Inherent limitations of the active device
121: An amplifier is said to suffer from distortion when its output is
a. Low
b. Noisy
c. Larger than its output
d. Different from its input
122: An ideal amplifier has
a. Noise figure of less than 1 db
b. Noise factor of unity
c. Output S/N more than input S/N
d. Noise figure of more than 0 db
123: Multistage amplifiers are used in order to achieve greater
a. Voltage amplification
b. Power gain
c. Frequency response
d. All of these
124: The decibel gain of a cascaded amplifier equals the
a. Product of equal gains
b. Sum of individual gains
c. Ratio of stage gains
d. Product of voltage and current gains
125: RC coupling is popular in low-level audio amplifiers because it
a. Has better low frequency response
b. Is inexpensive and needs no adjustments
c. Provides an output signal in phase with the input signal
d. Needs low voltage battery for collector supply
126: The most desirable feature of transformer coupling is its
a. Higher voltage gain
b. Wide frequency range
c. Ability to eliminate hum from the output
d. Ability to provide impedance matching between stages
127: The outstanding characteristic of s direct-coupled amplifier is its
a. Utmost economy
b. Temperature stability
c. Avoidance of frequency-sensitive components
d. Ability to amplify direct current and low frequency signals
128: Darlington pairs are frequently used in linear ICs because they
a. Do not require any capacitors or inductors
b. Have enormous impedance transformation capability
c. Can be readily formed from two adjacent transistors
d. Resemble emitter followers
129: When same input signal is applied to both the inputs of an ideal differential amplifier, the output
a. Depends on its CMMR
b. Is zero
c. Depends on its voltage gain
d. is determined by its symmetry
130: The common mode rejection ratio of an ideal differential amplifier is
a. Zero
b. Less than unity
c. Infinity
d. Greater than unity
131: Feedback in an amplifier always helps to
a. Control its input
b. Increase its gain
c. Decrease its input impedance
d. Stabilize its gain
132: Closed loop gain of a feedback amplifier is the gain obtained when
a. Its output terminals are closed
b. Negative feedback is applied
c. Feedback loop is closed
d. Feedback factor exceeds unity
133: A large sacrifice factor in a negative feedback amplifiers leads to
a. Inferior performance
b. Increased output impedance
c. Precise control over output
d. Characteristics impossible to achieve without feedback
134: Negative feedback in an amplifier
a. Lowers its lower 3db frequency
b. Raises its upper 3db frequency
c. Increases its bandwidth
d. All of these
135: A FET consists of a
a. Source
b. Drain
c. Gate
d. All of these
136: FETs have similar properties to
a. PNP transistors
b. NPN transistors
c. Thermionic valves
d. Uni-junction transistors
137: For small value of drain-to-source voltage, JFET behaves like a
a. Constant-current source
b. Resistor
c. Constant-voltage source
d. Negative resistance
38: In a JFET, the primary control on drain current is exerted by
a. Channel resistance
b. Size of depletion regions
c. Voltage drop across channel
d. Gate reverse bias
39: After $V_{DS}$ reaches pinch-off value VP in a JFET, the drain current ID becomes
a. Zero
b. Low
c. Saturated
d. Reversed
140: In a JFET the drain current is maximum when VGS is
a. Negative
b. Zero
c. Positive
d. Equals to
141: A JFET has a disadvantage of
a. Being noisy
b. Having small gain-bandwidth product
c. Possessing positive temperature coefficient
d. Having low input impedance
142: For the operation of enhancement only N-channel MOSFET, value of gate voltage has to be
a. Absence of its channel
b. Negative gate-source voltage
c. Depletion of current carriers
d. Extremely small leakage current of its gate capacitor
143: The main factor which makes a MOSFET most likely to breakdown duribg normal handling is its
a. Very low gate capacitance
b. High leakage current
c. High input resistance
d. a & c
144: In a DE-MOSFET drain current flows when gate voltage is
a. Positive
b. Negative
c. Zero
d. All of these
145: The positive-gate operation of an N-channel DE-MOSFET is known as……. Mode
a. Depletion
b. Enhancement
c. E-only
d. Normal
146: In an E-only MOSFET, drain current starts only when $V_{GS\left(th\right)}$ is
a. Positive
b. Negative
c. Zero
d. Greater than
147: Which semiconductor device acts like a diode and two resistors
a. SCR
b. Triac
c. Diac
d. UJT
148: An SCR conducts appreciable current when its ……. With respect to cathode
a. Anode and gate are both negative
b. Anode and gate are both positive
c. Anode is negative and gate is positive
d. Gate is negative and anode is positive
149: After firing an SCR the gating pulse is removed. The current in the SCR will
a. Remains the same
b. Immediately falls to zero
c. Rise up
d. Rise a little and then fall to zero
150: An SCR may be turned OFF by
a. Interrupting its anode current
b. Reversing polarity of its anode-cathode voltage
c. Low-current dropout
d. All of these
151: A Triac behaves like two
a. Inverse parallel-connected SCRs with common gate
b. Diodes in series
c. Four-layer diodes in parallel
d. Resistors and one diode
152: A Triac can be triggered into conduction by
a. Only positive voltage at either anode
b. Positive or negative voltage at either anode
c. Positive or negative voltage at gate
d. b & c
153: A Diac is equivalent to a
a. Pair of SCRs
b. Pair of four-layer SCRs
c. Diode and two resistors
d. Triac with two gates
154: An SCS has
a. Four layers and three terminals
b. Three layers and four terminals
c. Two anodes and two gates
d. One anode, one cathode and two gates
155: An SCS may be switched ON by a
a. Positive pulse at its anode
b. Negative pulse at its cathode
c. Positive pulse at its cathode gate G2
d. Positive pulse at its anode gate G1
156: An electronic oscillator is
a. Just like an alternator
b. Nothing but an amplifier
c. An amplifier with feedback
d. A converter of ac to dc energy
157: The frequency of oscillation of an elementary LC oscillatory circuit depends on
a. Coil resistance
b. Coil inductance
c. Capacitance
d. b & c
158: For sustaining oscillations in an oscillator
a. Feedback factor should be unity
b. Phase shift should be 0o or nπ
c. Feedback should be negative
d. a & b
159: In a transistor Hartley-oscillator
a. Inductive feedback is used
b. untapped coil is used
c. Entire coil is in the output circuit
d. No capacitor is used
160: A Colpitts-oscillator uses
a. Tapped coil
b. Inductive feedback
c. Tapped capacitance
d. No tuned LC circuit
161: In RC phase-shift oscillator circuits
a. There is no need for feedback
b. Feedback factor is less than unity
c. Pure sine-wave output is possible
d. Transistor parameters determine oscillation frequency
162: Wien bridge oscillator is most often used whenever
a. Wide range of high purity sine-waves are to be generated
b. High feedback ratio is needed
c. Square output waves are required
d. Extremely high resonant frequencies are required
