PULSE AND DIGITAL CIRCUITS (Common to ECE, BME, E.Con.E, ECC, ICE)

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II B.Tech II Semester (R07) Regular/supply Examinations, Apr- 2010

PULSE AND DIGITAL CIRCUITS (Common to ECE, BME, E.Con.E, ECC, ICE)

Answer any FIVE Questions All Questions carry equal marks

1 a) A symmetrical periodic square waveform with peak amplitude of ‘V’ volts, and time period of ‘T’ is applied to an RC integrator circuit as an input Find the steady state voltage across each element in the circuit

b) An ideal 1µs pulse is applied to an RC circuit Calculate and plot the output waveform when the upper 3 dB frequency is 10 MHz and 0.1 MHz

2 a) With the help of piecewise linear transfer characteristics, explain the operation of a clipping circuit at two independent levels

b) A pulse of 12 V and duration of 5 µs is applied to the circuit shown in Fig.1.1 Assuming that the capacitor in the circuit is initially uncharged, and the diode ‘D’ is ideal, determine v0(t) and sketch the same with respect to time

3 a) Explain how a transistor can be used as an electronic switch

b) Design a high speed transistor switch shown in Fig.1.2 for the given specifications:

VCC = 12, VBB =10, IC = 8 mA, hFE(min) = 30, and R2 = 3R1 Assume suitable saturation, cut off voltages for the given transistor

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6 a) Illustrate the terms ‘Synchronization’ and ‘frequency division’ of a sweep generator b) A free running relaxation oscillator has sweep amplitude of 100 V and a period of 1

ms synchronizing pulses are applied to the device such that breakdown voltage is lowered

by 50 V at each pulse The synchronizing pulse frequency is 4 kHz What is the amplitude and frequency of synchronized oscillator waveform?

7 a) With neat diagrams, explain the principle of operation of four diode bidirectional sampling gate Compare the performance of the circuit with that of six diode bidirectional sampling gate

b) Describe the errors encountered in series sampling and what is the design procedure that is adopted to minimize these errors

8 a) With the help of neat circuit diagram and truth table, explain the working of three input DTL NAND gate

b) What do you mean by ‘fan in’ and ‘fan out’? Discuss about the DTL NAND gate circuit which can improve Fan out of the gate

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1 a) A low pass RC network is fed by an exponential input voltage Obtain steady state voltage across both the elements

b) Prove that an RC low pass circuit behaves as reasonably good integrator if the time constant of the circuit is fifteen times the time period of an input signal of V sin(Ȧt)

2 a) Draw the clipper circuit using transistor, and explain the operation of it using suitable waveforms

b) Sketch the voltage v0(t) across the diode of Figure.2.1 for the input signal shown in the same Figure

3 a) What are the important parameters to be observed when the transistor is operated as electronic switch? Explain them

b) Discuss about the switching characteristics of a PN junction diode

4 a) With the aid of circuit diagram, obtain the mathematical relation that a collector coupled astable multivibrator can function as a voltage to frequency converter

b) Consider a symmetrical collector coupled astable multivibrator using n-p-n Si transistors The circuit and device parameters are: VCC = 6 V, RC = 560 ȍ, R = 5.6 k ȍ, C

= 50 pF, hFE = 40, and r’bb = 100 ȍ Calculate (i) the waveforms at the base and collector

of one transistor and plot to the scale Also find the recovery time and frequency of oscillations

5 a) Explain the working of transistor based Bootstrap time base generator circuit, and draw the necessary waveforms

b) In the circuit shown in Fig 2.2, VCC = 20 V, L = 200 mH, the inductors internal resistance is 20 ȍ, Rd = 200 ȍ For a 500 µs sweep, draw the waveforms of inductor current and the voltage between collector and emitter of the transistor Calculate slope

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6 a) How an astable multivi b) A symmetrical astable

10 V collector supply vol

is 750 µs are applied to source Find the minim synchronization Assume

7 a) With neat diagrams, sampling gate

b) Describe the operation chopper switch in ON sta c) Describe the operation

8 Write the following: (a) D NOR gates are universal g

ivibrator can be synchronized? Illustrate with wav

le multivibrator using Germanium transistors and oltage has a free period of 1ms Triggering pulse

to one base through a small capacitor from a nimum triggering pulse amplitude required

e that the timing portion of the base waveform is

s, explain the principle of operation of six dio

on of chopper amplifier Give the operation of th tate and in OFF state

n of balanced choppers

) DTL NAND gate, (b) RTL NOR gate, (c) Prove

l gates

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aveforms

d operating from a lses whose spacing

a high impedance

to achieve 1:1

is linear

diode bidirectional the transistor as a

ve that NAND and

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1 a) Derive the expression for the percentage tilt when the time constant of an RC high pass circuit is very large as compared to the period of input symmetrical square waveform b) When a ramp signal is transmitted through a linear RC network, the output departs from the input Deduce the relation for transmission error for different time constants of the circuit as compared to the duration of the ramp signal

2 a) List out the types of clamping circuits used in the industry Give the circuit diagram of each type Explain the operation of a clamping circuit whose output signal has negative offset

b) Design a diode clamper circuit to restore the positive peaks of 1 kHz input signal to a voltage level equal to 5V Assume that the diode voltage during forward bias condition is 0.7 V

3 a) Describe the sequence of events that lead to reverse recovery time, storage time, and transition time in a semiconductor diode

b) Calculate the output levels ‘v0’ of the circuit shown in Fig 3.1 for inputs vi = 0 V, and

vi = - 8V Verify whether the circuit acts as an inverter or not What is the maximum value dc current gain required Select standard junction voltages for the Si transistor during cut off and saturation, and assume an ideal diode in the circuit

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5 a) With the help of circuit diagram, explain the principle of operation of a constant current sweep circuit

b) Design a transistor bootstrap ramp generator to provide an output amplitude of 12 V over a time period of 2 ms The input signal is a negative going pulse with an amplitude

of 5 V, a pulse width of 2 ms and the time interval between pulses is 0.5 ms The load resistance is 2 kȍ and the ramp is to be linear within 1% The supply is to be ±15 V Assume hFE(min) = 80

6 a) Describe the frequency division employing a transistor monostable multivibrator b) A UJT sweep circuit operates with a valley voltage of 3 V and a peak voltage of 16 V

A sinusoidal synchronizing voltage of 2 V peak is applied between bases The intrinsic stand-off ratio is 0.5 If the natural frequency of the sweep is 1 kHz, over what range of synchronization signal frequency will the sweep remain in 1:1 synchronization with the synchronization signal?

7 a) Sketch circuit of a simple diode bidirectional sampling gate and describe its functioning with neat waveforms Obtain the expressions for gain A, and the two minimum control voltage levels

b) Describe the operation of chopper amplifier Give the operation of the transistor as a chopper switch in ON state and in OFF state

8 a) Realize two input TTL NAND gate truth table and explain its operation with suitable circuit diagram

b) With the help of neat circuit diagram and truth table, explain the working of diode logic AND gate, and RTL AND gate

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1 a) Give quantitative analysis of compensated and uncompensated attenuators Give suitable examples for each case

b) A 12 Hz symmetrical square wave whose peak- to-peak amplitude is 5V is impressed upon a high pass circuit whose lower 3 dB frequency is 15 Hz Determine the peak to peak amplitude of the output waveform Find the corner voltages of the output waveform Also sketch the input and output waveforms on the same scale

2 (a) State and explain clamping circuit theorem Discuss about the practical clamping circuit with suitable sketches

b) A rectangular waveform of Vp-p =10 V, with T1 = 2 ms, and T2 = 20 ms is applied to the dc restorer circuit The circuit has source resistance Rs = 0 ohms, diode forward resistance Rf =10 ȍ, cutin voltage VȖ = 0 V, Rr = , R = 500 ȍ, C = 0.1µF Compute the steady state output waveform Repeat the same for R = 1M ȍ

3 a) Define rise time, storage time, fall time, and turn off time in the case of transistor as a switch

b) Design a common emitter transistor switch operating with two power supplies VCC =

18 V, -VBB = -12 V The transistor is expected to operate at IC = 8 mA, and IB = 0.75 mA The static current gain is 25 Assume Si transistor, and R2 = 5R1

4 a) Explain the operation of a emitter bistable multivibrator circuit with suitable sketches b) Design a Schmitt trigger circuit to have UTP = 6 V, LTP = 3 V using silicon transistors whose hFE(min) = 40 Assume necessary data

5 a) Define the three errors that occur in a sweep circuit and obtain an expression for these errors for an exponential sweep circuit

b) Explain with suitable circuit diagram, the working of a UJT relaxation oscillator and obtain the expression for the intrinsic standoff ratio

6 a) Discuss about synchronization of a sweep circuit with symmetrical signals

b) How a monostable multivibrator circuit can be used for frequency division? Explain with suitable sketches

c) What do you mean by phase delay and phase jitters?

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8 Explain the following terms:

a) Realization of AND and OR gates using universal gates, b) What do you mean by ‘fan in’ and ‘fan out’? Discuss about the DTL NAND gate circuit which can improve ‘fan out’ of the gate

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Tiêu đề	Pulse And Digital Circuits (Common to ECE, BME, E.Con.E, ECC, ICE)
Trường học	University of Electronic Science and Technology of China
Chuyên ngành	Pulse and Digital Circuits (Common to ECE, BME, E.Con.E, ECC, ICE)
Thể loại	Textbook
Năm xuất bản	2010
Thành phố	Chengdu

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