JNTU
JNTU B.Tech III PULSE AND DIGITAL CIRCUITS Previous Question Paper (November/December - 2017 - R15)
Note: This question paper contains two parts A and B. 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 and may have a, b, c as sub questions.
Part A
Draw the response curve of an RC circuit for step and ramp inputs.
Answer
For a step input, the output of an RC circuit follows an exponential rise defined by v(t) = V(1 - e-t/RC). For a ramp input, the output follows a parabolic response defined by v(t) = at - aRC(1 - e-t/RC), where 'a' is the slope of the ramp.
Explain the working of low pass RC circuit as an integrator.
Answer
A low pass RC circuit acts as an integrator when the time constant RC is much larger than the pulse duration (RC >> T). Under this condition, the capacitor voltage remains small compared to the input voltage, allowing the output voltage to be proportional to the integral of the input signal, vo(t) ≈ (1/RC) ∫ vi(t) dt.
Write about diode clippers and their applications.
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Explain the effect of diode characteristics on clamping voltage.
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Explain the transistor switching times.
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Describe working of four diode sampling gate.
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Explain the working of multivibrators.
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Explain the working of Miller time base generators.
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Write about pulse synchronization in sweep circuits.
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Draw the circuit diagram for OR and AND gates using transistors.
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Part B
Discuss the response of low pass RC circuit to sinusoidal input signals with necessary expressions and wave forms.
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A symmetrical square wave whose peak to peak amplitude is 2V and average value is 0 is applied to RC integrating circuit. The time constant is half the period of the square wave. Find the peak to peak value of the output Voltage. Sketch the steady state output waveform.
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What is time constant of an RC circuit? Derive an expression for time constant of an RC circuit.
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What are the different Break downs of transistor and explain its operation along with block diagram.
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Discuss the series wave clipper and shunt wave clipper using diode along with relevant waveforms.
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Draw a neat diagram of emitter coupled clipper and explain its working. Write the applications of Comparators.
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Describe the series and shunt type diode clippers with the help of neat diagrams and mention their applications.
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What is meant by piece wise-linear approximation? Draw the V – I characteristics of junction diode on the basis of above approximation.
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Explain of Bipolar junction transistor as switch with help of neat diagram and discuss about transistor switching times.
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Explain the working of UJT relaxation oscillator and mention some important applications of thyristors.
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Explain the transistor switching times with typical diagram and discuss the break down voltage considerations of a transistor.
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Discuss the practical considerations in design of a transistor switch with help of neat diagram and explain the saturation parameters of a transistor.
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Discuss the principle of operation of transistor astable multivibrator with the help of neat diagram and draw the input output wave forms of an astable multivibrator.
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Describe the working of monostable multivibrator as a voltage to time convertor with help of neat diagram.
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Explain the operation of a monostable multivibrator with triggering circuits and wave forms and derive an expression for its pulse width.
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Design a Schmitt trigger circuit using n-p-n silicon transistor with following specifications: Vcc=12V, UTP=4V, LTP=2V, hfe=60, Ice=3mA, using relevant assumptions and empirical relationships.
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Explain the working UJT relaxation oscillator and Bootstrap sweep generator with neat diagrams and derive the expressions for their frequency.
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Derive an expression for sweep-speed error in Miller sweep circuit and compare between Miller and Bootstrap circuits.
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Explain the principle and working of astable and monostable relaxation oscillators with diagrams.
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Prove the De Morgan’s first and second theorems by the method of perfect induction method and write necessary truth tables.
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