# Electronic Circuits Unit wise Viva Short Questions and Answers PDF

## DEPARTMENT OF ECE QUESTION BANK SUBJECT NAME: ELECTRONICS CIRCUITS II UNIT I FEEDBACK AMPLIFIERS Part A (2Marks) 1. Define positive feedback? If the feedback signal is in phase with input signal, then the net effect of the feedback will increase the input signal given to the amplifier. This type of feedback is said to be positive or regenerative feedback. 2. Define negative feedback? If the feedback signal is out of phase with the input signal then the input voltage applied to the basic amplifier is decreased and correspondingly the output is decreased. This type of feedback is known as negative or degenerative feedback. 3. Define sensitivity? Sensitivity is defined as the ratio of percentage change in voltage gain with feedback to the percentage change in voltage gain without feedback. 4. What are the types of feedback? i. Voltage-series feedback ii. Voltage-shunt feedback iii. Current-series feedback iv. Current-shunt feedback 5. Define feedback? A portion of the output signal is taken from the output of the amplifier and is combined with the normal input signal. This is known as feedback. 6. Write the expression for input and output resistance of voltage series feedback amplifier. 7. Give an example for voltage-series feedback. The Common collector or Emitter follower amplifier is an example for voltage series feedback. 8. Give the properties of negative feedback. i. Negative feedback reduces the gain ii. Distortion is very much reduce Part-B (16 Marks)  1. What will happen when a step input voltage is applied to the high pass RC Circuit? (16) 2 .Explain the relevant information, how the negative feedback improves stability (16) reduce noise and increase input impedance? (16) 3. Explain voltage shunt feedback amplifiers? (16) 4. Explain current series feedback amplifiers? (16) UNIT II OSCILLATORS Part A (2Marks) 1. What is Oscillator circuit? A circuit with an active device is used to produce an alternating current is called an oscillator circuit. 2. What are the types of feedback oscillators? * RC-Phase shift Oscillator, * LC-Oscillators i. Tuned collector Oscillator ii. Tuned emitter Oscillator iii. Tuned collector base Oscillator iv. Hartley Oscillator v. Colpits Oscillator vi. Clap Oscillator 3. What are the conditions for oscillation? The total phase shift of an oscillator should be 360 o. For feedback oscillator it should satisfies Barhausen criterion. 4. Define Piezoelectric effect. When applying mechanical energy to some type of crystals called piezoelectric crystals the mechanical energy is converted into electrical energy is called piezoelectric effect. 5. What is Miller crystal oscillator? Explain its operation. It is nothing but a Hartley oscillator its feedback Network is replaced by a crystal. Crystal normally generate higher frequency reactance due to the miller capacitance are in effect between the transistor terminal. 6. Define Oscillator A circuit with an active device is used to produce an alternating current is called an oscillator circuit. Part-B (16 Marks) 1. With simple diagrams explain the operation of negative resistance oscillator using tunnel diode? (16) 2. Explain RC phase shift oscillator? (16) 3. Explain Clapp’s oscillator and derive the expression for frequency of oscillation. (16) Also explain how frequency stability can be improved Clapp’s oscillator. (16) 4. Explain Hartly oscillator and derive the equation for oscillation? (16) 5. Explain pierce crystal oscillator and derive the equation for oscillation? (16)\ UNIT III TUNED AMPLIFIERS Part A (2Marks) 1. What is a tuned amplifier? The amplifier with a circuit that is capable of amplifying a signal over a narrow band of frequencies Are called tuned amplifiers. 2. What are the different coil losses? Hysteresis loss Copper loss Eddy current loss 3. What is Q factor? It is the ratio of reactance to resistance. 4. What is dissipation factor? It is referred as the total loss within a component i.e1/Q 5. What is the classification of tuned amplifiers? Single tuned Double tuned Stagger tuned 6. What is a single tuned amplifier? An n amplifier circuit that uses a single parallel tuned circuit as a load is called single tuned amplifier. 7. What are the advantages of tuned amplifiers? They amplify defined frequencies. Signal to noise ratio at output is good They are suited for radio transmitters and receivers 8. What are the disadvantages of tuned amplifiers? The circuit is bulky and costly The design is complex. They are not suited to amplify audio frequencies. 9. What is neutralization? The effect of collector to base capacitance of the transistor is neutralized by introducing a signal that cancels the signal coupled through collector base capacitance. This process is called neutralization. 10. What are double tuned amplifiers? The amplifiers having two parallel resonant circuit in its load are called double tuned amplifiers. 11. What is a stagger tuned amplifier? It is a circuit in which two single tuned cascaded amplifiers having certain bandwidth are taken and their resonant frequencies are adjusted that they are separated by an amount equal to the bandwidth of each stage. Since resonant frequencies are displaced it is called stagger tuned amplifier. 12. What are the advantages of stagger tuned amplifier? The advantage of stagger tuned amplifier is to have better flat, wideband characteristics. 13. What are the different types of neutralization? 1. Hazeltine neutralization 2. Rice neutralization 3. Neutrodyne neutralization. 14. What is rice neutralization? It uses center tapped coil in the base circuit. The signal voltages at the end of tuned base coil are equal and out of phase. 15. What is unloaded Q? It is the ratio of stored energy to the dissipated energy in a reactor or resonator. converter. Part-B (16 Marks) 1. Explain in detail about single tuned amplifier (16) 2. Explain in detail about double tuned amplifier. (16) 3. Explain in detail about stagger-tuned amplifier (16) 4. Compare single tuned and double tuned amplifier (16) 5. Explain the different types of neutralization? (16) UNIT IV WAVE SHAPING AND MULTIVIBRATOR CIRCUITS Part A (2Marks) 1. What are the applications of mixer circuits? Used in radio receivers. Used to translate signal frequency to some lower frequency 2. What is up converter? When the mixer circuit is used to translate signal to high frequency, then it is called up 3. What is an amplifier? An amplifier is a device which produces a large electrical output of similar characteristics to that of the input parameters. 4. How are amplifiers classified according to the input? 1. Small – signal amplifier 2. Large – signal amplifier 5. How are amplifiers classified according to the transistor configuration? 1. Common emitter amplifier 2. Common base amplifier 3. Common collector amplifier 6. What is the different analysis available to analyze a transistor? 1. AC analysis 2. DC analysis 7. How can a DC equivalent circuit of an amplifier be obtained? By open circuiting the capacitor. 8. How can a AC equivalent circuit of a amplifier be obtained? By replacing dc supply by a ground and short- circuiting capacitors. 9, What is a Multivibrator? The electronic circuits which are used to generate nonsinusoidal waveforms are called Multivibrators. 10, Name the types of Multivibrators? Bistable Multivibrator, Monostable Multivibrator,Astable Multivibrator 11, How many stable states do bistable Multivibrator have? Two stable states. 12, When will the circuit change from stable state in bistable Multivibrator ? when an external trigger pulse is applied, the circuit changes from one stable state to another. 13. What are the different names of bistable Multivibrator? Eccles Jordan circuit, trigger circuit, scale-of-2 toggle circuit, flip-flop and binary. 14. What are the applications of bistable Multivibrator? It is used in the performance of many digital operations such as counting and storing of theBinary information. It also finds applications in the generation and processing of pulse – type waveforms. 15. What are the other names of monostable Multivibrator? One-shot, Single-shot, a single-cycle, a single swing, a single step Multivibrator, Univibrator. Part-B (16 Marks) 1. Explain bistableMultivibrator and its types? (16) 2. Explain about speedup capacitors or commutating capacitors. (16) 3. Explain about Monostable Multivibrator. (16) 4. Explain about collector coupled astableMultivibrator. (16) 5. Explain emitter coupled astableMultivibrator. (16) 6. Write in detail about Schmitt Trigger circuit? (16) UNIT-V BLOCKING OSCILLATOR AND TIME BASE GENERATOR 1.Define Blocking Oscillator? A special type of wave generator which is used to produce a single narrow pulse or train of pulses. 2. What are the two important elements of Blocking Oscillator? Transistor and pulse transformer 3. What are the applications of blocking Oscillator? It is used in frequency dividers, counter circuits and for switching the other circuits. 4. Give the expression for co-efficient of coupling K=M/ LpLs M-> Mututal Inductance Lp -> Primary Inductance Ls -> Secondary Inductance 5. Give the formula for transformation ratio n= Ns/Np = transformation ratio Ns= Secondary Turns; Np= Primary turns 6. Define rise time It is defined by the time required by the pulse to rise from 10% of its amplitude to 90% of its amplitude. 7. Define overshoot. It is the amount by which the output exceeds its amplitude during first attempt. 8. Define flat top response. The position of the response between the trailing edge and the leading edge. 9. Define droop or a tilt The displacement of the pulse amplitude during its flat response is called droop or a tilt. Part-B (16 Marks) 1. Explain bistableMultivibrator and its types? (16) 2. Explain about speedup capacitors or commutating capacitors. (16) 3. Explain about Monostable Multivibrator. (16) 4. Explain about collector coupled astableMultivibrator. (16) 5. Explain emitter coupled astableMultivibrator. (16) 6. Write in detail about Schmitt Trigger circuit? (16)

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