JNTU
JNTU B.Tech II PULSE AND DIGITAL CIRCUITS Previous Question Paper (May - 2019 - 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
What is a ringing circuit? What are its applications?
Answer
A ringing circuit is an underdamped RLC series circuit that produces a damped sinusoidal oscillation when excited by a step input. Its applications include generating high-frequency oscillations, triggering circuits, and acting as a time-base generator component.
How high pass RC network works as differentiator.
Answer
A high-pass RC circuit acts as a differentiator when the time constant (RC) is very small compared to the input pulse width. Under this condition, the capacitor charges and discharges rapidly, making the output voltage proportional to the rate of change of the input voltage, represented by the formula:
Draw the circuit diagram of positive clipper.
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State clamping circuit theorem.
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What is the significance of transistor breakdown voltages in transistor switch?
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How a silicon controlled Rectifier works as switch?
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What are the values of gain for ideal miller and Boot strap circuits.
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Mention the methods to improve linearity in time base generators.
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What are the sweep circuits and what are their applications?
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What are universal gates? Realize XOR gate using universal gates.
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Part B
Explain how a low pass RC circuit act as an integrator with suitable diagrams and show their response for a square wave.
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A symmetrical square wave of ±5V at a frequency of 5 kHz is applied to a high- pass RC circuit with a cut off frequency of 20KHz. Calculate the steady state output voltage and draw the steady state Input/output voltage wave forms.
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Discuss the response of a high pass RC circuit to step, ramp, exponential and sinusoidal input signals with necessary expressions and wave forms.
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Explain the working of an attenuator with circuit diagram and describe how it is used in a CRO probe.
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Write about clipping and clamping of wave forms. Classify different types of clipper circuits give their circuits and explain their operation with help of transfer characteristics.
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Explain the working of transistor based voltage comparators with neat circuit diagram and describe the functions of voltage comparators.
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Design a diode clamper to restore a d. c voltage level of +3 V to an input signal of peak to peak value of 10V. Assume drop across the diode as 0.6V.
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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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What is meant by piece wise-linear approximation? Draw the V-I characteristics of a junction diode on the basics of the above approximation.
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Explain the basic operating principles of sampling gates and draw the circuit diagrams of unidirectional and bi directional sampling gates.
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Discuss the effect of temperature variations on saturation parameters and switching times of transistor switch.
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Explain the operation of a mono-stable multivibrator with triggering and wave forms and also 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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Briefly list out various methods of generating time base wave forms and explain in detail about transistor Miller time base generator with help of neat diagram.
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Explain the terms sweep error, transmission error and displacement error in general time base generator and obtain expressions for them.
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Explain the working of monostable relaxation circuit as a frequency divider with neat circuit diagram and necessary wave forms.
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Explain the principle of operation of synchronization of sweep circuits with symmetrical signal with suitable wave forms.
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Explain the working of basic 3 input (diode transistor logic) DTL NAND gate with help of neat diagram.
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Design a relaxation oscillator using 2N3980 UJT with 20V supply for an output frequency of 5KHz and calculate its output amplitude.
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