JNTU
JNTU B.Tech II ELECTRONIC CIRCUITS Previous Question Paper (December - 2018 - R13)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
Part A
Compare CB, CE and CC amplifiers in terms of input and output impedances.
Answer
| Configuration | Input Impedance | Output Impedance |
|---|---|---|
| CB | Low | Very High |
| CE | Medium | Medium |
| CC | High | Low |
What is the effect of negative feedback on Nonlinear distortion?
Answer
Negative feedback significantly reduces nonlinear distortion in amplifiers. If D is the distortion without feedback and Df is the distortion with feedback, then Df = D / (1 + Aβ), where Aβ is the loop gain. As the feedback factor increases, the distortion is suppressed by the factor (1 + Aβ).
State Miller’s theorem.
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Define the parameters fβ, fα and fT.
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What are the applications of Multivibrators?
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What is the effect of diode characteristics on clamping voltage?
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Why heat sinks are required?
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What is mean by cross-over distortion?
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Why damper diodes are used at the output of the transistor switches?
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How the saturation parameters of transistor are vary with temperature?
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Part B
Draw the circuit diagram and low frequency equivalent circuit of common collector amplifier and derive the equations for voltage gain, current gain, input resistance and output resistance.
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Prove that AIf = AI for voltage series feedback, with Rs=0.
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An amplifier with open-loop voltage gain Av=1000±100 is available. It is necessary to have an amplifier whose voltage gain varies by no more than ±0.1 percent. Find the reverse transmission factor of the feedback network used and also find the gain with feedback?
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Prove that the CC short circuit current gain as a function of frequency is given by
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A silicon transistor has hfe= 100, and gm =50mA/V at room temperature. If the values of hybrid π capacitances are Ce=100pf and Cc=3pF, find the values of fβ and fT.
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What is the main limitation of the collector coupled astable multivibrator to be used as a square wave generator?
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Explain the operation of a collector coupled transistor monostable multivibrator with the help of neat circuit diagram and waveforms.
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Explain the working of various diode clipping circuits that operate with two independent clipping levels with neat circuit diagrams and waveforms.
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A transistor supplies 0.85W to a 4K load. The zero-signal dc collector current is 31mA, and the dc collector current with signal is 34mA. Determine the percent second-harmonic distortion.
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What is the maximum conversion efficiency of a class B push-pull amplifier? Prove it.
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A signal v(t) = Ve^(-t/T) is applied to a double differentiator. Find the output if τ = R1C1 = R2C2. Plot the response and locate any minima.
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Consider a pulse waveform as input to the RC high pass filter. Obtain the expression for the negative jump in the response at t=tp.
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Explain how the diode is used as a switch and indicate the switching regions in diode V-I characteristics.
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What are the different timing parameters of transistor switch? Define them and draw the switching response.
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