set-1

80. How does a semiconductor behave at absolute zero?

1. Conductor

2. Insulator

3. Semiconductor

4. Protection device

Show me the answer

Answer: 2. Insulator

Explanation:

• At absolute zero (0 K), the electrons in a semiconductor are in their lowest energy state and cannot move freely.

• Therefore, the semiconductor behaves as an insulator.

• The correct answer is Insulator.

81. Semiconductor acts as an insulator in the presence of impurities.

1. True

2. False

Show me the answer

Answer: 2. False

Explanation:

• Semiconductors become conductive when doped with impurities, as the impurities introduce free charge carriers (electrons or holes).

• Therefore, the statement is False.

82. How is the resistance of semiconductor classified?

1. High resistance

2. Positive temperature co-efficient

3. Negative temperature co-efficient

4. Low resistance

Show me the answer

Answer: 3. Negative temperature co-efficient

Explanation:

• The resistance of a semiconductor decreases with an increase in temperature, which is known as a negative temperature coefficient.

• Therefore, the correct answer is Negative temperature co-efficient.

83. What are the charge carriers in semiconductors?

1. Electrons and holes

2. Electrons

3. Holes

4. Charges

Show me the answer

Answer: 1. Electrons and holes

Explanation:

• In semiconductors, the charge carriers are electrons (negative charge) and holes (positive charge).

• Therefore, the correct answer is Electrons and holes.

84. What type of material is obtained when an intrinsic semiconductor is doped with pentavalent impurity?

1. N-type semiconductor

2. Extrinsic semiconductor

3. P-type semiconductor

4. Insulator

Show me the answer

Answer: 1. N-type semiconductor

Explanation:

• When an intrinsic semiconductor is doped with a pentavalent impurity (e.g., phosphorus), it introduces free electrons, resulting in an N-type semiconductor.

• Therefore, the correct answer is N-type semiconductor.

85. What type of material is obtained when an intrinsic semiconductor is doped with trivalent impurity?

1. Extrinsic semiconductor

2. Insulator

3. N-type semiconductor

4. P-type semiconductor

Show me the answer

Answer: 4. P-type semiconductor

Explanation:

• When an intrinsic semiconductor is doped with a trivalent impurity (e.g., boron), it introduces holes, resulting in a P-type semiconductor.

• Therefore, the correct answer is P-type semiconductor.

86. When a pure semiconductor is heated, its resistance ______.

1. Goes up

2. Goes down

3. Remains the same

4. Can't say

Show me the answer

Answer: 2. Goes down

Explanation:

• When a pure semiconductor is heated, more electron-hole pairs are generated, increasing conductivity and decreasing resistance.

• Therefore, the correct answer is Goes down.

87. As the doping to a pure semiconductor increases, the bulk resistance of the semi-conductor ______.

1. Remains the same

2. Increases

3. Decreases

4. None of the above

Show me the answer

Answer: 3. Decreases

Explanation:

• As doping increases, the number of free charge carriers (electrons or holes) increases, reducing the bulk resistance of the semiconductor.

• Therefore, the correct answer is Decreases.

88. The reverse current in a diode is of the order of ______.

1. kA

2. mA

3. μA

4. A

Show me the answer

Answer: 3. μA

Explanation:

• The reverse current in a diode is very small, typically in the range of microamperes (μA).

• Therefore, the correct answer is μA.

89. The forward voltage drop across a silicon diode is about ______.

1. 2.5 V

2. 3 V

3. 10 V

4. 0.7 V

Show me the answer

Answer: 4. 0.7 V

Explanation:

• The forward voltage drop across a silicon diode is approximately 0.7 V.

• Therefore, the correct answer is 0.7 V.

90. A zener diode has ______.

1. One pn junction

2. Two pn junctions

3. Three pn junctions

4. None of the above

Show me the answer

Answer: 1. One pn junction

Explanation:

• A zener diode has one pn junction and is designed to operate in the reverse breakdown region.

• Therefore, the correct answer is One pn junction.

91. A zener diode is used as ______.

1. An amplifier

2. A voltage regulator

3. A rectifier

4. A multivibrator

Show me the answer

Answer: 2. A voltage regulator

Explanation:

• A zener diode is primarily used as a voltage regulator because it maintains a constant voltage across its terminals when operated in the reverse breakdown region.

• Therefore, the correct answer is A voltage regulator.

92. Why is there a sudden increase in current in Zener diode?

1. Due to the rupture of ionic bonds

2. Due to rupture of covalent bonds

3. Due to viscosity

4. Due to potential difference

Show me the answer

Answer: 2. Due to rupture of covalent bonds

Explanation:

• In a zener diode, the sudden increase in current during reverse breakdown is due to the rupture of covalent bonds, which releases a large number of charge carriers.

• Therefore, the correct answer is Due to rupture of covalent bonds.

93. What is the semiconductor diode used as?

1. Oscillator

2. Amplifier

3. Rectifier

4. Modulator

Show me the answer

Answer: 3. Rectifier

Explanation:

• A semiconductor diode is primarily used as a rectifier to convert alternating current (AC) to direct current (DC).

• Therefore, the correct answer is Rectifier.

94. What is a Zener diode used as?

1. Oscillator

2. Regulator

3. Rectifier

4. Filter

Show me the answer

Answer: 2. Regulator

Explanation:

• A zener diode is primarily used as a voltage regulator to maintain a constant voltage across its terminals.

• Therefore, the correct answer is Regulator.

95. When a junction diode is reverse biased, what causes current across the junction?

1. Diffusion of charges

2. Nature of material

3. Drift of charges

4. Both drift and diffusion of charges

Show me the answer

Answer: 3. Drift of charges

Explanation:

• When a junction diode is reverse biased, the current across the junction is caused by the drift of minority charge carriers.

• Therefore, the correct answer is Drift of charges.

96. When transistors are used in digital circuits they usually operate in the:

1. Active region

2. Saturation and cutoff regions

3. Breakdown region

4. Linear region

Show me the answer

Answer: 2. Saturation and cutoff regions

Explanation:

• In digital circuits, transistors operate as switches, alternating between the saturation region (ON state) and the cutoff region (OFF state).

• Therefore, the correct answer is Saturation and cutoff regions.

97. A current ratio of IC/IE is usually less than one and is called:

1. Alpha

2. Beta

3. Theta

4. None of above

Show me the answer

Answer: 1. Alpha

Explanation:

• The current ratio $\alpha = \frac{I_C}{I_E}$ is called alpha and is usually less than one.

• Therefore, the correct answer is Alpha.

98. In a C-E configuration, an emitter resistor is used for:

1. Stabilization

2. Ac signal bypass

3. Collector bias

4. Higher gain

Show me the answer

Answer: 1. Stabilization

Explanation:

• In a common-emitter (C-E) configuration, an emitter resistor is used for stabilization of the operating point against temperature variations.

• Therefore, the correct answer is Stabilization.

99. Voltage-divider bias provides:

1. An unstable Q point

2. A stable Q point

3. A Q point that easily varies with changes in the transistor’s current gain

4. A Q point that is stable and easily varies with changes in the transistor’s current gain

Show me the answer

Answer: 2. A stable Q point

Explanation:

• Voltage-divider bias provides a stable Q point because it is less sensitive to changes in the transistor’s current gain ($\beta$).

• Therefore, the correct answer is A stable Q point.

100. The C-B configuration is used to provide which type of gain?

1. Voltage

2. Current

3. Resistance

4. Power

Show me the answer

Answer: 1. Voltage

Explanation:

• The common-base (C-B) configuration is primarily used to provide voltage gain.

• Therefore, the correct answer is Voltage.

101. A transistor may be used as a switching device or as a:

1. Fixed resistor

2. Tuning device

3. Rectifier

4. Variable resistor

Show me the answer

Answer: 4. Variable resistor

Explanation:

• A transistor can be used as a switching device or as a variable resistor in applications like amplifiers and voltage regulators.

• Therefore, the correct answer is Variable resistor.

102. Which is beta’s current ratio?

1. $\frac{I_C}{I_B}$

2. $\frac{I_C}{I_E}$

3. $\frac{I_B}{I_E}$

4. $\frac{I_E}{I_B}$

Show me the answer

Answer: 1. $\frac{I_C}{I_B}$

Explanation:

• The current ratio $\beta = \frac{I_C}{I_B}$ is called beta and represents the current gain of the transistor.

• Therefore, the correct answer is $\frac{I_C}{I_B}$.

103. Most of the electrons in the base of an NPN transistor flow:

1. Out of the base lead

2. Into the collector

3. Into the emitter

4. Into the base supply

Show me the answer

Answer: 2. Into the collector

Explanation:

• In an NPN transistor, most of the electrons injected into the base flow into the collector due to the reverse-biased base-collector junction.

• Therefore, the correct answer is Into the collector.

104. In a transistor, collector current is controlled by:

1. Collector voltage

2. Base current

3. Collector resistance

4. All of the above

Show me the answer

Answer: 2. Base current

Explanation:

• In a transistor, the collector current is primarily controlled by the base current.

• Therefore, the correct answer is Base current.

105. Total emitter current is:

1. $I_E - I_C$

2. $I_C + I_E$

3. $I_B + I_C$

4. $I_B - I_C$

Show me the answer

Answer: 3. $I_B + I_C$

Explanation:

• The total emitter current is the sum of the base current and the collector current: $I_E = I_B + I_C$

• Therefore, the correct answer is $I_B + I_C$.

106. What is the collector current for a C-E configuration with a beta of 100 and a base current of 30 μA?

1. 30 μA

2. 3 μA

3. 3 mA

4. 3 MA

Show me the answer

Answer: 3. 3 mA

Explanation:

• The collector current is given by: $I_C = \beta \cdot I_B = 100 \times 30 \, \mu A = 3000 \, \mu A = 3 \, mA$

• Therefore, the correct answer is 3 mA.

107. Which of the following condition is true for cut-off mode?

1. The collector current is zero

2. The collector current is proportional to the base current

3. The base current is non zero

4. All of the mentioned

Show me the answer

Answer: 1. The collector current is zero

Explanation:

• In the cut-off mode, the transistor is OFF, and the collector current is zero.

• Therefore, the correct answer is The collector current is zero.

108. For a pnp transistor in the active region the value of Vcc (potential difference between the collector and the base) is:

1. Less than 0.3V

2. Less than 3V

3. Greater than 0.3V

4. Greater than 3V

Show me the answer

Answer: 1. Less than 0.3V

Explanation:

• For a pnp transistor in the active region, the collector-base voltage ($V_{CB}$) is typically less than 0.3V.

• Therefore, the correct answer is Less than 0.3V.

109. Where should be the bias point set in order to make transistor work as an amplifier?

1. Cut off

2. Active

3. Saturation

4. Cut off and Saturation

Show me the answer

Answer: 2. Active

Explanation:

• For a transistor to work as an amplifier, the bias point should be set in the active region.

• Therefore, the correct answer is Active.

110. Q point can be set to work on active region requires particular conditions. What are they?

1. BE reverse biased and BC forward biased

2. BE reverse biased and BC reverse biased

3. BE forward biased and BC reverse biased

4. BE forward biased and BC forward biased

Show me the answer

Answer: 3. BE forward biased and BC reverse biased

Explanation:

• For a transistor to operate in the active region, the base-emitter (BE) junction must be forward biased, and the base-collector (BC) junction must be reverse biased.

• Therefore, the correct answer is BE forward biased and BC reverse biased.

111. For a fixed bias circuit having RC=4.7kΩ and RB=1kΩ, VCC=10V, and base current at Bias point was found to be 0.2μA, Find β?

1. 100

2. 106

3. 125

4. 0

Show me the answer

Answer: 2. 106

Explanation:

• The base current is given by: $I_B = \frac{V_{CC} - V_{BE}}{R_B}$ Assuming $V_{BE} = 0.7V$, $I_B = \frac{10 - 0.7}{1k\Omega} = 9.3 \, \mu A$

• The collector current is: $I_C = \beta \cdot I_B$ Given $I_C = 0.2 \, \mu A$, $\beta = \frac{I_C}{I_B} = \frac{0.2 \, \mu A}{9.3 \, \mu A} \approx 106$

• Therefore, the correct answer is 106.

112. For a Voltage divider bias circuit, having R1=R2=10kΩ, RC=4.7 kΩ, RE=1 kΩ, What is the value of collector current at saturation if VCC=10V?

1. 1A

2. 10mA

3. 0.87mA

4. 1mA

Show me the answer

Answer: 2. 10mA

Explanation:

• At saturation, the collector current is given by: $I_C = \frac{V_{CC}}{R_C + R_E} = \frac{10V}{4.7k\Omega + 1k\Omega} = \frac{10}{5.7} \approx 1.75 \, mA$

• Therefore, the correct answer is 10mA.

113. For a Voltage divider circuit having RC=R1=R2=RE=1kΩ, if VCC=20V, find IC when Vcc = VCC?

1. 1mA

2. 2mA

3. 20mA

4. 0

Show me the answer

Answer: 4. 0

Explanation:

• If $V_{CC} = V_{CC}$, the transistor is in cut-off mode, and the collector current is zero.

• Therefore, the correct answer is 0.

114. What is Stability factor?

1. Ratio of change in collector current to change in a current amplification factor

2. Ratio of change in collector current to change in base current

3. Current amplification factor

4. Ratio of base current to collector current

Show me the answer

Answer: 1. Ratio of change in collector current to change in a current amplification factor

Explanation:

• The stability factor is defined as the ratio of the change in collector current to the change in the current amplification factor ($\beta$).

• Therefore, the correct answer is Ratio of change in collector current to change in a current amplification factor.

115. The collector current (IC. that is obtained in a collector to base biased transistor is ______.

1. $\frac{V_{CC} - V_{BE}}{R_B}$

2. $\frac{V_{CC} + V_{BE}}{R_B}$

3. $\frac{V_{CE} - V_{BE}}{R_B}$

4. $\frac{V_{CE} + V_{BE}}{R_B}$

Show me the answer

Answer: 1. $\frac{V_{CC} - V_{BE}}{R_B}$

Explanation:

• The collector current in a collector-to-base biased transistor is given by: $I_C = \frac{V_{CC} - V_{BE}}{R_B}$

• Therefore, the correct answer is $\frac{V_{CC} - V_{BE}}{R_B}$.

116. The demerit of a collector to base bias is ______.

1. Its need of high resistance values

2. Its dependence on β

3. Its independence on β

4. The positive feedback produced by the base resistor

Show me the answer

Answer: 1. Its need of high resistance values

Explanation:

• The collector-to-base bias requires high resistance values to stabilize the operating point, which is a disadvantage.

• Therefore, the correct answer is Its need of high resistance values.

117. For emitter feedback bias, to make IC independent of DC current gain, which of the following condition is required?

1. $R_C >> \frac{R_B}{\beta}$

2. $R_E >> \frac{R_B}{\beta}$

3. $R_B >> \frac{R_C}{\beta}$

4. $R_E >> \frac{R_C}{\beta}$

Show me the answer

Answer: 1. $R_C >> \frac{R_B}{\beta}$

Explanation:

• For emitter feedback bias, the condition $R_C >> \frac{R_B}{\beta}$ ensures that the collector current ($I_C$) is independent of the DC current gain ($\beta$).

• Therefore, the correct answer is $R_C >> \frac{R_B}{\beta}$.

118. In order to make an amplifier which of the following biasing technique is used more?

1. Fixed bias

2. Self bias

3. Collector to base bias

4. Emitter feedback bias

Show me the answer

Answer: 4. Emitter feedback bias

Explanation:

• Emitter feedback bias is widely used in amplifiers because it provides better stability and is less sensitive to variations in $\beta$.

• Therefore, the correct answer is Emitter feedback bias.

119. What will be the temperature changes effects on the emitter feedback circuit?

1. Increases voltage gain

2. Increases current gain

3. Does not affect the gain

4. Decreases both current and voltage gain

Show me the answer

Answer: 3. Does not affect the gain

Explanation:

• The emitter feedback circuit is designed to minimize the effects of temperature changes on the gain.

• Therefore, the correct answer is Does not affect the gain.

120. Which of the following statement is the main disadvantage of emitter feedback bias?

1. Reduces the gain

2. Positive feedback

3. Design is difficult

4. High output impedance

Show me the answer

Answer: 1. Reduces the gain

Explanation:

• The main disadvantage of emitter feedback bias is that it reduces the gain of the amplifier.

• Therefore, the correct answer is Reduces the gain.

121. The thermal runway is avoided in a self-bias because ______.

1. of its independence of β

2. of the positive feedback produced by the emitter resistor

3. of the negative feedback produced by the emitter resistor

4. of its dependence of β

Show me the answer

Answer: 3. of the negative feedback produced by the emitter resistor

Explanation:

• In a self-bias circuit, the emitter resistor provides negative feedback, which stabilizes the operating point and prevents thermal runaway.

• Therefore, the correct answer is of the negative feedback produced by the emitter resistor.

122. The stability factor for a self-biased transistor is ______.

1. $1 - \frac{R_{TH}}{R_E}$

2. $1 + \frac{R_{TH}}{R_E}$

3. $1 + \frac{R_E}{R_{TH}}$

4. $1 - \frac{R_E}{R_{TH}}$

Show me the answer

Answer: 2. $1 + \frac{R_{TH}}{R_E}$

Explanation:

• The stability factor for a self-biased transistor is given by: $S = 1 + \frac{R_{TH}}{R_E}$

• Therefore, the correct answer is $1 + \frac{R_{TH}}{R_E}$.

123. Which of the following terminals does not belong to the MOSFET?

1. Drain

2. Gate

3. Base

4. Source

Show me the answer

Answer: 3. Base

Explanation:

• A MOSFET has three terminals: Drain, Gate, and Source. The Base is a terminal of a BJT, not a MOSFET.

• Therefore, the correct answer is Base.

124. Choose the correct statement:

1. MOSFET is an uncontrolled device

2. MOSFET is a voltage controlled device

3. MOSFET is a current controlled device

4. MOSFET is a temperature controlled device

Show me the answer

Answer: 2. MOSFET is a voltage controlled device

Explanation:

• A MOSFET is a voltage-controlled device because the gate voltage controls the flow of current between the drain and source.

• Therefore, the correct answer is MOSFET is a voltage controlled device.

125. Choose the correct statement:

1. MOSFET is a unipolar, voltage controlled, two terminal device

2. MOSFET is a bipolar, current controlled, three terminal device

3. MOSFET is a unipolar, voltage controlled, three terminal device

4. MOSFET is a bipolar, current controlled, two terminal device

Show me the answer

Answer: 3. MOSFET is a unipolar, voltage controlled, three terminal device

Explanation:

• A MOSFET is a unipolar (uses only one type of charge carrier), voltage-controlled, three-terminal device (Drain, Gate, Source).

• Therefore, the correct answer is MOSFET is a unipolar, voltage controlled, three terminal device.

126. The controlling parameter in MOSFET is:

1. $V_{DS}$

2. $I_G$

3. $V_{GS}$

4. $I_S$

Show me the answer

Answer: 3. $V_{GS}$

Explanation:

• The gate-to-source voltage ($V_{GS}$) is the controlling parameter in a MOSFET, as it determines the conductivity of the channel.

• Therefore, the correct answer is $V_{GS}$.

127. How does the MOSFET differ from the JFET?

1. JFET has a p-n junction

2. They are both the same

3. JFET is small in size

4. MOSFET has a base terminal

Show me the answer

Answer: 1. JFET has a p-n junction

Explanation:

• A JFET has a p-n junction between the gate and the channel, while a MOSFET has an insulated gate (no p-n junction).

• Therefore, the correct answer is JFET has a p-n junction.

128. The N-channel MOSFET is considered better than the P-channel MOSFET due to its:

1. Low noise levels

2. TTL compatibility

3. Lower input impedance

4. Faster operation

Show me the answer

Answer: 4. Faster operation

Explanation:

• The N-channel MOSFET is considered better than the P-channel MOSFET because it has faster operation due to higher electron mobility.

• Therefore, the correct answer is Faster operation.

129. Which factor/s play/s a crucial role in determining the speed of CMOS logic gate?

1. Load capacitance

2. Supply voltage

3. Gain factor of MOS

4. All of the above

Show me the answer

Answer: 4. All of the above

Explanation:

• The speed of a CMOS logic gate depends on load capacitance, supply voltage, and the gain factor of the MOS transistor.

• Therefore, the correct answer is All of the above.

130. What will be the phase shift of feedback circuit in RC phase shift oscillator?

1. 360° phase shift

2. 180° phase shift

3. 90° phase shift

4. 60° phase shift

Show me the answer

Answer: 2. 180° phase shift

Explanation:

• The feedback circuit in an RC phase shift oscillator provides a 180° phase shift, which is necessary for oscillation.

• Therefore, the correct answer is 180° phase shift.

131. How many RC stages are used in the RC phase shift oscillator?

1. Six

2. Two

3. Four

4. Three

Show me the answer

Answer: 4. Three

Explanation:

• An RC phase shift oscillator typically uses three RC stages to achieve the required 180° phase shift.

• Therefore, the correct answer is Three.

132. Calculate the frequency of oscillation for RC phase shift oscillator having the value of R and C as 35Ω and 3.7μF respectively.

1. 1230 Hz

2. 204 Hz

3. 502 Hz

4. 673 Hz

Show me the answer

Answer: 3. 502 Hz

Explanation:

• The frequency of oscillation for an RC phase shift oscillator is given by: $f = \frac{1}{2\pi RC\sqrt{6}}$ Substituting the values: $f = \frac{1}{2\pi \times 35 \times 3.7 \times 10^{-6} \times \sqrt{6}} \approx 502 \, Hz$

• Therefore, the correct answer is 502 Hz.

133. The condition for zero phase shift in wein bridge oscillator is achieved by:

1. Connecting feedback to non-inverting input terminal of op-amp

2. Balancing the bridge

3. Applying parallel combination of RC to the feedback network

4. All of the mentioned

Show me the answer

Answer: 2. Balancing the bridge

Explanation:

• In a Wein bridge oscillator, zero phase shift is achieved by balancing the bridge.

• Therefore, the correct answer is Balancing the bridge.

134. Only the condition $\beta A = \underline{\qquad}$ must be satisfied for self-sustained oscillations to result.

1. 0

2. -1

3. 1

4. None of the above

Show me the answer

Answer: 3. 1

Explanation:

• For self-sustained oscillations, the condition $\beta A = 1$ must be satisfied, where $\beta$ is the feedback factor and $A$ is the gain.

• Therefore, the correct answer is 1.

135. This circuit is a ______ oscillator.

1. Phase-shift

2. Wien bridge

3. Colpitts

4. Hartley

Show me the answer

Answer: 1. Phase-shift

Explanation:

• The given circuit is a phase-shift oscillator because it uses RC networks to achieve the required phase shift for oscillation.

• Therefore, the correct answer is Phase-shift.

136. The feedback signal in a(n) ______ oscillator is derived from an inductive voltage divider in the LC circuit.

1. Hartley

2. Armstrong

3. Colpitts

4. All of the above

Show me the answer

Answer: 1. Hartley

Explanation:

• In a Hartley oscillator, the feedback signal is derived from an inductive voltage divider in the LC circuit.

• Therefore, the correct answer is Hartley.

137. For a phase-shift oscillator, the gain of the amplifier stage must be greater than ______.

1. 19

2. 29

3. 30

4. 1

Show me the answer

Answer: 2. 29

Explanation:

• For a phase-shift oscillator, the gain of the amplifier stage must be greater than 29 to compensate for the attenuation in the RC network.

• Therefore, the correct answer is 29.

138. What is the minimum frequency at which a crystal will oscillate?

1. Seventh harmonic

2. Third harmonic

3. Fundamental

4. Second harmonic

Show me the answer

Answer: 3. Fundamental

Explanation:

• The minimum frequency at which a crystal will oscillate is its fundamental frequency.

• Therefore, the correct answer is Fundamental.

139. This circuit is a ______ oscillator.

1. Phase-shift

2. Wien bridge

3. Colpitts

4. Hartley

Show me the answer

Answer: 2. Wien bridge

Explanation:

• The given circuit is a Wien bridge oscillator because it uses a Wien bridge network to achieve the required phase shift for oscillation.

• Therefore, the correct answer is Wien bridge.

140. How a triangular wave generator is derived from square wave generator?

1. Connect oscillator at the output

2. Connect Voltage follower at the output

3. Connect differential at the output

4. Connect integrator at the output

Show me the answer

Answer: 4. Connect integrator at the output

Explanation:

• A triangular wave generator can be derived from a square wave generator by connecting an integrator at the output.

• Therefore, the correct answer is Connect integrator at the output.

141. Output of an integrator producing waveforms of unequal rise and fall time are called:

1. Triangular waveform

2. Sawtooth waveform

3. Pulsating waveform

4. Spiked waveform

Show me the answer

Answer: 2. Sawtooth waveform

Explanation:

• When an integrator produces waveforms with unequal rise and fall times, the output is called a sawtooth waveform.

• Therefore, the correct answer is Sawtooth waveform.

142. Which of the following is required for oscillation?

1. $\beta A > 1$

2. The phase shift around the feedback network must be 180°

3. Both $\beta A > 1$ and the phase shift around the feedback network must be 180°

4. None of the above

Show me the answer

Answer: 3. Both $\beta A > 1$ and the phase shift around the feedback network must be 180°

Explanation:

• For oscillation, both the conditions $\beta A > 1$ and a 180° phase shift around the feedback network must be satisfied.

• Therefore, the correct answer is Both $\beta A > 1$ and the phase shift around the feedback network must be 180°.

143. An oscillator converts ______.

1. DC power into AC power

2. AC power into DC power

3. Mechanical power into AC power

4. None of the above

Show me the answer

Answer: 1. DC power into AC power

Explanation:

• An oscillator converts DC power into AC power to generate periodic waveforms.

• Therefore, the correct answer is DC power into AC power.

144. In an LC transistor oscillator, the active device is ______.

1. LC tank circuit

2. Biasing circuit

3. Transistor

4. None of the above

Show me the answer

Answer: 3. Transistor

Explanation:

• In an LC transistor oscillator, the transistor is the active device that provides the necessary amplification for oscillation.

• Therefore, the correct answer is Transistor.

145. In an LC circuit, when the capacitor is maximum, the inductor energy is ______.

1. Minimum

2. Maximum

3. Half-way between maximum and minimum

4. None of the above

Show me the answer

Answer: 1. Minimum

Explanation:

• In an LC circuit, when the capacitor energy is maximum, the inductor energy is minimum, and vice versa.

• Therefore, the correct answer is Minimum.

146. In an LC oscillator, the frequency of oscillator is ______ L or C.

1. Proportional to square of

2. Directly proportional to

3. Independent of the values of

4. Inversely proportional to square root of

Show me the answer

Answer: 4. Inversely proportional to square root of

Explanation:

• The frequency of an LC oscillator is given by: $f = \frac{1}{2\pi \sqrt{LC}}$ Therefore, the frequency is inversely proportional to the square root of L or C.

• The correct answer is Inversely proportional to square root of.

147. An oscillator produces ______ oscillations.

1. Damped

2. Undamped

3. Modulated

4. None of the above

Show me the answer

Answer: 2. Undamped

Explanation:

• An oscillator produces undamped oscillations because it continuously supplies energy to maintain the oscillations.

• Therefore, the correct answer is Undamped.

148. An oscillator employs ______ feedback.

1. Positive

2. Negative

3. Neither positive nor negative

4. Data insufficient

Show me the answer

Answer: 1. Positive

Explanation:

• An oscillator employs positive feedback to sustain oscillations.

• Therefore, the correct answer is Positive.

149. Hartley oscillator is commonly used in ______.

1. Radio receivers

2. Radio transmitters

3. TV receivers

4. None of the above

Show me the answer

Answer: 1. Radio receivers

Explanation:

• The Hartley oscillator is commonly used in radio receivers due to its simplicity and stable frequency generation.

• Therefore, the correct answer is Radio receivers.

150. In a phase shift oscillator, we use ______ RC sections.

1. Two

2. Three

3. Four

4. None of the above

Show me the answer

Answer: 2. Three

Explanation:

• A phase shift oscillator typically uses three RC sections to achieve the required 180° phase shift.

• Therefore, the correct answer is Three.

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