InterviewSolution

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This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.

101.	The most important consideration in power amplifier is ________(a) Biasing the circuit(b) Impedance Matching(c) Collector Efficiency(d) To keep the transformer coolI got this question in a national level competition.Origin of the question is Class B Output Stage topic in section Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» The correct option is (c) Collector Efficiency To ELABORATE: The most important consideration in POWER amplifier is Collector Efficiency. The pulsating DC applied to power amplifier causes hum in the circuit. For EVERY stage of power amplifier, the collector efficiency is CONSIDERED most important.

102.	Which transformer is used for impedance matching in transistor coupled amplifier?(a) step-up(b) step-down(c) same turn ratio(d) differentturn ratioI have been asked this question by my school teacher while I was bunking the class.I need to ask this question from Multistage Amplifier in section Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» The correct CHOICE is (B) step-down The best explanation: Usually the impedance of an output device is a few ohms WHEREAS output impedance of the transistor is several 100 ohms. In order to match the impedance a step down TRANSFORMER of proper turn’s ratio is used. The impedance of secondary of the transformer is made EQUAL to the load impedance and primary impedance equal to the output impedance of the transistor.

103.	When a transistor is in cut off________(a) Maximum voltage appears across transistor(b) Maximum voltage appears across load(c) Maximum current flows(d) Least current flowsThis question was addressed to me by my school principal while I was bunking the class.This key question is from Class B Output Stage topic in chapter Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» Right answer is (a) Maximum VOLTAGE appears ACROSS transistor The explanation is: A transistor in cutoff MODE is off – there is no collector CURRENT, and therefore no emitter current. It almost looks like an OPEN circuit. Thus Maximum voltage appears across the transistor.

104.	When no signal is applied, the approximate collector efficiency of class A power amplifier is ____________(a) 25%(b) 10%(c) 0%(d) 50%I got this question in unit test.This is a very interesting question from Class A Output Stage in division Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» Correct ANSWER is (c) 0% The EXPLANATION: The efficiency of a class A amplifier is dependent UPON the input signal. The relation is direct. Therefore, with no input signal applied(i.e. input signal= 0); the efficiency will be equal to ZERO.

105.	The size of a power transistor is made considerably large to ________(a) Provide easy handling(b) Dissipate heat(c) Facilitate connections(d) Larger GainI had been asked this question in an international level competition.This intriguing question comes from Class B Output Stage topic in portion Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» Correct CHOICE is (b) Dissipate heat The EXPLANATION is: Power amplifiers handle large signals as compared to voltage amplifiers. The SIZE of power transistors is MADE CONSIDERABLY large to dissipate heat. Low efficiency of power amplifiers results in more battery consumption.

106.	Which of the push-pull amplifiers is presently the most popular form of the class B power amplifier?(a) Quasi-complementary(b) Transformer-coupled(c) Complementary-symmetry(d) SymmetryThe question was posed to me during an interview for a job.This is a very interesting question from Classification of Output Stages in section Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» The correct choice is (a) Quasi-complementary For explanation: In class B operation, a push-pull CONNECTION is obtained using either a TRANSFORMER coupling or by using complementary (or quasi-complementary) operation with npn and pnp transistors to provide operation on opposite polarity cycles. While transformer operation can provide opposite cycle signals, the transformer itself is QUITE large in MANY application.

107.	Which operation class is generally used in radio or communications?(a) A(b) B(c) C(d) DThe question was posed to me in a national level competition.The doubt is from Classification of Output Stages in portion Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» Correct option is (c) C To explain: In radio or COMMUNICATIONS, generally class C is used in case of HIGH level modulation.High level modulation uses class C amplifiers in a broadcast AM TRANSMITTER and only the final stage or final two stages are modulated, and all the EARLIER stages can be driven at a constant level.

108.	What is the voltage gain of a differential amplifier with active load?(a) 1(b) 0(c) ∞(d) Cannot be determinedI got this question in an online interview.Question is taken from Differential Amplifier with Active Load topic in chapter Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» Right answer is (a) 1 For EXPLANATION: If all the resistor values are of the EQUAL VALUE, then the circuit will have a voltage gain equal to exactly one or unity. Hence it is also called as a Unity Gain Differential amplifier with active load. The output voltage expression would be the DIFFERENCE between the two voltages.

109.	A feedback circuit usually employs which type of circuit?(a) Resistive(b) Inductive(c) Capacitive(d) ShuntI have been asked this question in quiz.This interesting question is from Properties of Negative Feedback in division Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» The correct option is (a) Resistive For explanation I would say: Using a resistor in the NEGATIVE FEEDBACK LOOP we can control the gain in two ways- For inverting AMPLIFIER MODE; Vout = – (Rf/R) Vin For non- inverting amplifier mode; Vout = (1+Rf/R) Vin.

110.	Voltage-divider bias has a relatively stable Q-point, as does_________(a) base bias(b) collector-feedback bias(c) emitter bias(d) both base and emitter biasI had been asked this question during an online exam.My enquiry is from Input Bias and Offset Currents of the Bipolar Differential Amplifier topic in portion Differential and Multistage Amplifiers of Electronic Devices & Circuits
Answer» Correct choice is (b) collector-feedback bias The BEST I can explain: The collector feedback BIASING is also beta-independent. It has the same circuit as the voltage DIVIDER biasing except there is only one RESISTOR used other than load resistor Rc. However, voltage divider biasing has the ADVANTAGE that its stability factor is greater than that of collector feedback biasing.

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