Reg. No.

MANIPAL INSTITUTE OF TECHNOLOGY Manipal University

I / II SEMESTER B.E. (E & C) DEGREE END SEMESTER EXAMINATION NOV / DEC-2008

SUBJECT: BASIC ELECTRONICS (ECE- 101/102) TIME: 3 HOURS MAX. MARKS: 50

ECE – 101/102 Page 1 of 2

Instructions to candidates

• Answer ANY FIVE full questions. • Missing data may be suitably assumed.

1A. The Zener diode in the circuit of Figure 1A regulates at 50 V over a range of diode currents from 5 to 40 mA. The supply voltage V=200V. i) Calculate R to allow voltage variation from a load current I2 =0 up to IL max the maximum possible value of IL. What is IL max ? ii) If R is as in part (i) and the load current is set at IL = 25 mA, What are the limits between which V may vary with out loss of regulation in the circuit. 1 B. What are the components of currents in a semiconductor? Explain with suitable expressions. 1 C. Draw and explain the input and output characteristics of a NPN transistor in CE configuration and indicate the region of operation. (5+3+2) 2 A. Explain the operation of full wave bridge rectifier with capacitor filter, using suitable circuit and waveforms. Also derive expressions for the ripple factor. 2 B. An FM has a carrier frequency of 90MHz and highest frequency of the FM signal is 90.08MHz when modulated by a signal of frequency 5 KHz. Determine

i) Frequency deviation and carrier swing ii) Modulation index iii) Bandwidth 2 C. Simplify the Boolean functions and realize the simplified circuit using only NOR gates. ABC+AB’C+ABC’ (5+3+2) 3 A. A silicon diode has a reverse saturation current of 10 nA at 200 C. Find out the diode

bias voltage when the current is 3 mA. If the bias voltage is maintained constant what is the current through the diode when the temperature is 1000 C ?

3 B. Explain the steps in 2’s complement subtraction. Subtract the decimal number 71

from 82 using 2’s complement method. 3 C. Prove that NAND gate is an Universal gate. (4+3+3)

ECE – 101/102 Page 2 of 2

4 A. Design a voltage divider biasing circuit using silicon transistor, given the following parameters: Ic = 1 MA, VCE 6V, VCC = 12 v β = 100, Vbe = 0.7 4 B. Design an averaging amplifier using single op-amp to average 3 input voltages V1, V2 and V3. Assume the gain required is 2. 4 C. What is meant by extrinsic semiconductors? What are the different types? Explain how they are obtained. (4+3+3) 5 A. Show how op amp can be used as i) adder ii) Integrator. Derive expressions for the outputs. 5 B. What is meant by break down? What are the different types? List and compare them. 5 C. Convert the following hexadecimal numbers to binary, Octal and decimal numbers i) 144 ii) FA07 (4+3+3) 6 A. A carrier of 1 MHz with 400 W of power is amplitude modulated with a sinusoidal

signal of 2500 Hz. The depth of modulation is 75 %. Calculate the side band frequencies, the bandwidth and the power in the side bands and the total power in the modulated wave.

6 B. Draw the circuit of an S-R flip flop and explain its operation using truth table. What is it’s draw back? 6 C. Draw the circuit diagram of a R-C coupled transistor amplifier with self bias. Explain

the function of each component. Also explain how the circuit amplifies a small signal. (4+3+3)

Reg. No.

MANIPAL INSTITUTE OF TECHNOLOGY Manipal University,

I / II SEMESTER B.E. (E & C) DEGREE END SEMESTER EXAMINATION NOV / DEC-2008

SUBJECT: BASIC ELECTRONICS (ECE- 101/102) 22 November 2008

TIME: 3 HOURS MAX. MARKS: 50

ECE – 101/102 Page 1 of 2

Instructions to candidates

• Answer ANY FIVE full questions. • Missing data may be suitably assumed.

1A Write the expression for current in a PN junction diode and explain each term.

Also plot the V-I characteristics for Ge & Si diodes to the same scale and mark all the salient points.

1B Draw the circuit diagram of NPN transistor in Common Emitter configuration,

sketch the output characteristics and indicate the regions of operation. Also explain how the transistor parameters are measured from the output characteristics. (4 + 6)

2A For the circuit shown in Fig Q2A, α1 = 0.98, α2 = 0.96, VCC = 24V, RC = 120Ω, IE2=100mA. Neglecting ICBO, determine all the transistor currents and output voltage.

2B Derive an expression for the instantaneous value of the Amplitude Modulated signal and draw the frequency spectrum. (6 +4)

3A Determine ICQ, IBQ & VCEQ for a Silicon transistor with β = 50 in a self bias circuit. The circuit component values are VCC = 20V, RC = 2 KΩ, RE = 0.1 KΩ, R1 = 100 KΩ and R2 = 5 KΩ

3B Obtain an expression for the closed loop voltage gain in the case of inverting and non inverting amplifier using Op-Amp. (6 +4)

4A Simplify the following Boolean functions:

( )( ) ( )CABCBAACABii

BABAi

+++

+++

)(

4B A silicon diode operates at a forward voltage of 0.4V. Calculate the factor by which the current will be multiplied when the temperature is increased from 25°C to 150°C

4C Design an adder circuit to obtain an output voltage given by the expression,

V0 = -[0.5V1+0.8V2+2V3], where V1, V2 and V3 are the input voltages.

ECE – 101/102 Page 2 of 2

4 D Draw the circuit of a J-K flip flop using NAND gates and explain its operation

with the help of truth table. (2+2+3+3) 5A Draw the circuit diagram of a full wave rectifier with capacitor filter and explain

the operation using relevant waveforms. Also derive the expression for the ripple factor

5B A Zener diode regulates at 50V over a range of diode current from 5 to 40mA.If the input voltage is 200V, calculate RS to get voltage regulation from a load current IL=0 to ILMAX.

(6 + 4) 6A Perform the following mathematical operations: (i) (456.32)10 = (?)2 = (?)8= (?)16= (?)BCD (ii) (11011)2 + (11101)2 = (?)2 (iii) (10101)2 - (11001)2 using 2’s complement arithmetic (2+1+2) 6B Draw the truth table of a full adder and implement the circuit using only NAND gates. (5)

Reg. No.

MANIPAL INSTITUTE OF TECHNOLOGY Manipal University

SECOND SEMESTER B.E. DEGREE END SEMESTER EXAMINATION

MAY/ JUNE – 2009

SUBJECT: BASIC ELECTRONICS (ECE 101/102)

(REVISED CREDIT SYSTEM)

TIME : 3 HOURS MAX. MARKS : 50

ECE 101/102 Page 1 of 2

Instructions to candidates

Answer ANY FIVE full questions.

Missing data may be suitably assumed.

1A Derive the expression for Amplitude modulated signal and draw its frequency

spectrum.

-3-

1B What is doping? Explain crystal lattice structure, energy band diagram and

conduction in p-type semiconductor.

-5-

1C Sketch the ideal load and line regulation characteristics of a Zener Regulator

-2-

2A With a neat circuit diagram, explain the working of full wave bridge rectifier.

Derive the expressions for its ripple factor and efficiency.

-5-

2B A self bias circuit uses Ge transistor with RC = 220Ω, RE = 100Ω, VCC = 10V,

Estimate the value of R1 and R2 required to provide a base current of 150μA,

such that ICQ = 8mA and VCEQ = 7.425 V.

-5-

3A With the help of energy band diagram distinguish between Insulator,

Conductor and a Semiconductor.

-2-

3B Write the logical symbol, truth table and output expression for AND gate. Also

realize AND gate using Diodes.

-4-

3C Implement Vo = -0.5(V1 + V2 – V3) using one OPAMP. -4-

4A A full wave rectifier with 1500 μF capacitor across load resistor has maximum

input voltage of 30V at 50Hz and peak to peak ripple voltage of 0.2 volt. Find

the dc load current.

-4-

4B Explain the working of Integrator and Differentiator circuits using OPAMP. -4-

4C Explain two types breakdown mechanism in Diodes. -2-

ECE 101/102 Page 2 of 2

5A Perform the following:

i) (F69.D3)16 – (A25.68)16 = (?)10

ii) (13.25)10 – (26.37)10 using Binary 1’s complement arithmetic

-4-

5B A 15KHz audio signal is used to frequency modulate 100MHz carrier signal

causing a carrier frequency deviation of 75KHz. Determine

i) Modulation index

ii) Bandwidth of the modulated signal

-3-

5C What do you mean by DC load line? What is its importance? Explain and

draw the DC load line for a fixed bias CE configuration.

-3-

6A Write the truth table of the full adder and obtain the simplified expression for

Sum and Carry. Realize carry output using NAND gates only.

-5-

6B For a Zener network Rs = 520Ω, VZ = 15V, Vi = 20± 5V. Find the minimum

and maximum value of RL so that the Zener diode remains in the ON state.

IZmin = 1mA, PZMax = 8W

-5-

*****

Reg. No.

MANIPAL INSTITUTE OF TECHNOLOGY Manipal University

SECOND SEMESTER B.E. DEGREE END SEMESTER EXAMINATION

MAY/ JUNE – 2009

SUBJECT: BASIC ELECTRONICS (ECE 101/102)

(REVISED CREDIT SYSTEM)

22 May 2009

TIME : 3 HOURS MAX. MARKS : 50

ECE 101/102 Page 1 of 2

Instructions to candidates

Answer ANY FIVE full questions.

Missing data may be suitably assumed.

1A For an OPAMP when V1 = 0.5 mV and V2 = -0.5mV, Vo = 8V. For the same

OPAMP, when V1 = V2 = 1mV, Vo = 12mV. Calculate CMRR in dB. Assume

V1 & V2 to be non inverting and inverting inputs respectively.

-3-

1B Write Boolean expression & truth table of Exclusive OR gate and implement

this gate using only NAND Gates

-5-

1C Three amplifiers with voltage gains 10, 100 & 1000 are connected in cascade.

Find (i) the output voltage when the input voltage is 10 μV

(ii) The overall gain in decibels

-2-

2A A carrier of 1MHz with 400 watts of power is amplitude modulated with a

sinusoidal signal of 2500 Hz. The depth of modulation is 75%. Calculate the

bandwidth and power of the sidebands & the total power in the modulated

wave. Derive the formula used.

-5-

2B Draw the Input and Output VI characteristics of PNP transistor in CB Mode &

explain.

-5-

3A A bar of intrinsic semiconductor (i.e., Silicon) has a cross sectional area of

2.5 x 10-4

m2. The free electron density is 1.5 x 10

16 per m

3. How long the bar

be in order that the current in the bar be 1.2mA when 9 Volts is applied across

it? Assume μn = 0.14 m2 /V-S, μp = 0.05 m

2 /V-S.

-4-

3B Starting from fundaments derive the expression for FM signal -3-

3C A silicon diode has reverse saturation current of 12 nA at 20oC. Find the diode

current when it is forward biased by 0.65V. Find the Diode current when the

temperature rises to 100 o

C.

-3-

ECE 101/102 Page 2 of 2

4A Simplify the Boolean expressions:

(a) F = XY + XYZ + XY’Z + X’YZ

(b) F = XYZ + X’Y+XYZ’

-4-

4B Explain the working of Inverting amplifier, Non inverting amplifier &

Inverting summer using OPAMP.

-6-

5A With a neat sketch explain the VI characteristics of Zener diode and illustrate

its application as a voltage regulator.

-3-

5B A sinusoidal voltage of 130V peak-to-peak is applied to a half wave rectifier,

with load resistance of 1 K-Ohm. If the cut in voltage is 0.7V and forward

resistance is 30 Ohm, Find i) Peak, dc and rms values of current ii) dc output

power and ac input power.

-4-

5C State and prove De Morgan’s theorem -3-

6A Design a voltage divider biasing circuit using silicon transistor, given the

following parameters:

IC = 1mA, VCE = 6V, VCC = 12V, VB = VCC /10, R2 = 2K, β = 100, VBE = 0.7V

-5-

6B Explain the terms: doping, mobility, conductivity, drift current & diffusion

current

-5-

*****

Reg. No.

MANIPAL INSTITUTE OF TECHNOLOGY

MANIPAL UNIVERSITY

FIRST SEMESTER BE DEGREE END SEMESTER EXAMINATIO N NOV /DEC 2009

SUBJECT: BASIC ELECTRONICS (ECE-101/102) (REVISED CREDIT SYSTEM)

TIME: 3 HOURS MAX. MARKS: 50

ECE-101/102 Page 1 of 2

Instructions to candidates

Answer any FIVE Full questions.

Missing data may be suitably assumed.

1A. Explain positive logic AND gate with help of a circuit using discrete

components.

1B. Write the block diagram of OPAMP and explain function and

requirements of each block.

1C. With help of circuit diagram and waveforms explain working of center

tapped full wave rectifier. Compare this with full wave bridge rectifier. (3+3+4)

2A. Write the function table of JK flip flop. Draw the logic diagram of four

bit serial shift register using JK flip flop and explain. Sketch output of each flip flop for an input of 1011 assuming initially all the flip flop are

reset.

2B. Explain a voltage regulator circuit. Explain load and line regulation of

this circuit. 2C. If α =0.98 ,VBE=0.7V and IE

= 2mA, find R1in the circuit shown in fig. (2C).

Fig. (2C)

(3+3+4)

3A. The output waveform of a full wave rectifier is a saw tooth in nature with peak value of 10V. If RL = 100Ω , C = 1000µF, and power line frequency is 50 Hz, calculate load current and peak to peak value of the

ripple voltage.

3B. A carrier of amplitude 5V and frequency 90MHz is frequency modulated by a sinusoidal voltage of amplitude 5V and frequency 15KHz. The frequency sensitivity is 1Hz/V. Calculate the frequency deviation and

modulation index.

ECE-101/102 Page 2 of 2

3C. What is amplitude modulation? Derive equation for AM output in time

domain. Sketch sinusoidally modulated AM wave for modulation index m =1, m <1 and m >1. (3+3+4)

4A. What is load line and Q point? Where do you choose the operating point

for amplifier and why?

4B. Simplify the following and implement using only NAND gates.

DCBAABCDDCBACDBADBCADCBACDBAf

4C. Design a circuit for the following output using single OPAMP.

V0 = -0.5 V1 + V2 + 0.5V3 (3+3+4)

5A.An amplifier rated at 40 W output is connected to a 10 speaker. Calculate the input power required for full power output if the power

gain is 25 dB. Calculate the input voltage for rated output if the amplifier voltage gain is 40 dB.

5B. A bar of Silicon with intrinsic electron density 1.5x1016 electrons/m3 is

doped until the electron density becomes 9x1022 electrons/m3. The mobilities are given as µn=0.13 m2/Vs and µp=0.05 m2/Vs. (i) Find the

hole density of the extrinsic material (ii) Is the extrinsic material n-type or p-type (iii) Find the extrinsic conductivity.

5C. Write the circuit diagram of RC coupled amplifier. Mention the role of

each component. Sketch the frequency response. Give reasons for drop in gains at low frequencies and high frequencies. (3+3+4)

6A. Draw the circuit diagram of OPAMP adder and derive the expression for output.

6B. Perform the following (i) (157. 625)10 - (28. 5)10 using binary 2’s complement arithmetic

(ii) (7865. 543)10 = ( ? )2 = ( ? )8 = (?)16

6C. Sketch VO1 and VO2 for the

circuit shown in fig. (6C) indicating frequency and amplitude. Explain working

of the circuit. Fig. (6C)

(3+3+4)

********

Reg. No.

MANIPAL INSTITUTE OF TECHNOLOGY

MANIPAL UNIVERSITY

FIRST SEMESTER BE DEGREE END SEMESTER EXAMINATIO N NOV/DEC 2009

SUBJECT: BASIC ELECTRONICS (ECE-101/102)

(REVISED CREDIT SYSTEM) TIME: 3 HOURS MAX. MARKS: 50

ECE-101/102 Page 1 of 2

Instructions to candidates

Answer any FIVE Full questions.

Missing data may be suitably assumed.

1A. Simplify the following Boolean expression and realize using NAND gates.

DCBAABCDDCBACDBADBCADCBACDBAf

1B. Half wave rectifier with capacitor filter has to supply an average voltage of 30V to

900Ω load. Calculate the rms input voltage and value of capacitor needed to get ripple factor of 0.05, assuming f = 50Hz

1C. Explain the need for modulation.

1D. Define α and β. Derive the relationship between them (3+3+2+2)

2A. In the circuit shown in figure a silicon transistor is used with = 45. VCE= 5V. Find R.

Fig. (2A)

2B. Write the block diagram of communication system and explain function of each block.

2C. A Si diode has reverse saturation current of12 nA at 20oC. (a) Find the diode current when it is forward biased by 0.65 V. (b) Find the diode current when the temperature

rises to 100oC. (3+3+4)

3A. Perform the following

(i) (257.75)10 - (128.825)10 using binary 2’s complement arithmetic (ii) (ABCD)16 = ( ? )10 = ( ? )2 = ( ? )8

3B. For a differential amplifier, the input voltages are v1 =10 mV and v2 = 8mV.If the differential gain is 5000. Calculate the output voltage when the CMRR is 80 dB.

3C. Primary voltage to a transformer with turns ratio is 5:1 is 120V, 60Hz. This is applied to bridge rectifier employing 4 identical diodes with forward voltage drops 0.6V and

forward resistance 15Ω . Assume transformer secondary resistance of 10 Ω and the load

ECE-101/102 Page 2 of 2

resistance of 500Ω. Calculate average and rms load voltage, efficiency, ripple factor, PIV rating and frequency of output waveform. (3+3+4)

4A. The zener diode in a regulator circuit has a breakdown voltage of 15 V and power

rating of 0.5 W. If the input voltage is 40 V, what is the minimum value of series resistance that prevents zener diode from being destroyed?

4B. Sketch VO1 and VO2 for the circuit shown in fig (4B) indicating

frequency and amplitude. Explain the function of the circuit.

Fig.(4B)

4C. Potential difference of 10V is applied across the ends of pure bar of silicon of cross

sectional area of 0.4 x 10-3m2 and length of 0.6x10-2 m . The intrinsic carrier concentration is 1.5x1016 electrons/m3 . Assuming µn=0.14 m2 /vs. and µp=0.005 m2/vs, e=1.6x 10-19 coulombs. Calculate (i) Electric field in the specimen. (ii)drift velocity of

electrons and holes (iii)total current density (iv)total current (v)conductivity(vi) resistivity (vii) bulk resistance of the bar. (3+3+4)

5A. Explain qualitatively how transistor functions as amplifier. Define the terms gain

factor and gain in decibels. Three amplifiers with gains 20dB, 30 dB and 40 dB are

connected in series. What is the total gain of the amplifier? Determine output voltage for an input of 10 mVolts

5B. Design a circuit for the following output using single OPAMP. V0 = -0.5 V1 + V2

5C. In a silicon transistor employing voltage divider bias following parameters are given:

IC = 1 mA, VCE = 6 V, VCC = 12 V, VB = VCC/10, R2 = 2K, = 100, VBE = 0.7 V. Determine the values of RC, R! and RE. Write the circuit diagram. (3+3+4)

6A. What is frequency modulation. Derive time domain equation for FM. Comment on the

band width.

6B. Starting from the equation for AM wave, derive the equation for total power of AM

signal. A 360W carrier is simultaneously modulated by two audio waves with percentage modulation of 55 and 65 respectively. Find the modulation index and total power radiated and power in each sideband. Assume RL=1Ω.

6C. With the help of energy band diagrams classify solids.

6D. What is half adder? Write the functional table and logical expressions for sum and carry. (3+3+2+2)

**********************