# Sem B.E. Degree Examination, May June 2010 Basic Electronics

Max. Marks: 100

|rany FIVE full questions, choosing at least two questions from each part.

ir all objective type questions only on OMR sheet page 5 of the answer booklet. f\$r jo objective type questions on sheets other than OMR will not be valued

PART-A

Iie correct answer from the following :

Semiconductor materials have____________ bonds.

JJCovalent     B) Mutual    C) Metal ic

function breakdown occurs with

r-.

^Forward bias B) Reverse bias C) Active bias %. silicon diode, reverse current is usually !ero^  B) Very large C) Very small

a Zener diode ^Forward voltage rating is high Negative resistance characteristic exists fSharp breakdown occurs at low reverse voltage lone of the above.

D) Ionic.

D) under high temperature. D) In the breakdown region.

i diagram and wavefomi, explain the working principle of full wave rectifier. (08 Marks) wave rectifier is used to convert 230 V AC in to DC across a load of 1 k Q. The

sfomier used is 230 V/12 volts. The DC resistance of the transformer used is 12D. and

■ &

nesresistance of the diode is 22 Q. Compute : mmr output voltage

f :The rms value of the output voltage pple factor ^Rectification efficiency.

fose the correct answer from the following :

– Loadline of a transistor circuit

> i*                                                                                                                                                                                                                                                                                                                          m                                            C*

a curved line         B) Has a-ve slope

not contain Q point D) Gives graphical relation between Ic and Ib-

D) l-a =

base region of p-n-p transistor, the main stream of current is

Hole current B) Electron current U) Saturation current D) Breakdown current.

fhe transistor operating point is chosen along the

j&aw the current components which flow in a transistor. Also derive the equation for lc in as of adc, Icbo and IB.          (08 Marks)

Bg|g|!^raw the input and output characteristics of CE circuit. Explain active, saturation and cut oil MBRpgions.                                                                                                      0 (03 Marla)

Choose the correct answer from the following :

i)   A transistor is a

A) Two terminal device B) Reverse biased device

C)    Three terminal device D) Modulated device.

ii)    Biasing means

A) Heating the junction B) Applying voltages C) Discharging D) Destroying.

iii)     Stability factor for a fixed bias circuit is

A)                                                                                      1 + a             B) 1 – a      C)l+P      D)l-0.

iv)    The operating point must be    for proper operation of the transistor

A)                                                                                     High              B) Increasing  C) Stable D) Decreasing.

(04 Marks)

Give the circuit for i) Collector to base bias ii) emitter current bias. Also compare basic bias circuits.                          (08 Marks).

For the circuit shown in Fig. Q3(c) using Si transistor with P = 50, draw the d.c loadline and determine the operating point.        (08 Ma

Choose the correct answer from the following :

i)   The situation of drain current becoming just saturated is called

d[) Cutoff.

B)     Saturation C) Pinch off device

B)    Switching C) Negative

A) Amplifying    B) Switching C) Negative D) Blocking.

iii)    The minimum point in VI characteristic of UJT is known as   point

A) Negative      B) Valley    C) Latching D) Conducting.

iv)    The factor r| of UJT is known as    ratio.

A) ON           B) Pulse     C) Negative D) Intrinsic stand-off.

(04 MaiWith the help of equivalent circuit and characteristics, explain the working principle of

(08 Maj

Draw two transistor equivalent circuit of SCR. Also plot V-I characteristic and exp] various regions of operation.      (08 Maj

PART-B

1. a.                    Choose the correct answer from the following :

i)    The criteria for producing Oscillations are known as criteria.

A) Doppler B) Bark housen C) Miller D) Band width.

ii)     A quartz crystal may be represented by an equivalent circuit consisting of a circuit.

A) RC        B) LC           C) RLC D) RL.

iii)     The oscillating circuit is also called as

A) Differential B) Tank      C) Logic t D) CRT.

iv)    Unit of gain in logarithmic scale is called

A)                                                      Watt            B) Joul    C) Bel   D) Decibel.

1. b.                     With circuit, explain the working of BJT RC phase shift oscillator.
2. c.                      With circuit, explain the working of two stage RC coupled amplifier and draw its

tse the correct answer from the following : inverting amplifier is one that produces _ foliage.

|h 45°                            B) 90°                               C) 360°                                      D) 180°.

op-amp shorted between inverting tenninal and output terminal is called if) Adder            B) Integrator   C) Voltage-follower D) inverter.

§)”The op-amp can amplify

if) AC signals only B) DC signals only C) both AC and DC signals D) None of these, frhe op-amp integrator uses

§|) Inductors B) Miller effect C) Sinusoidal inputs D) Hysteresis.

(04 Marks)

Draw the circuit, using op-amp, for ) Integrator    ii) Differentiator iii) Adder

v’jth diagram, explain main parts of CRT.

Ihoose the correct answer from the following-f- e l’s complement of 1010 gives 111           B) 0001 C)0010

;The number 12 in octal is equivalent to decimal 20 B) 12     C)10

I In binary numbers, shifting the binary point one place to 0 Devides by 2 B) decreases by 10 C) Increases by represent 35 in binary, number of bits required is

B)                                                                                                                                              5   C)4

<plain the need for modulation, ‘norm the following : f240,n =

D) 1110.

D)   4. the right

0 D) Multiplies by 2.

(04 Marks) (08 Marks)

0.2315,0 =

33I28 -_

32198,0 =

bose the correct answer from the following : e expression for half adder carry C with inputs A and B is given by

) A + B        B) AB           C) A B           D) None of these.

:A + AB =

AB            B) A           C) B             D) 1 + A.

P universal gates are_ and_______

‘ ) NOT and NOR B) AND and OR C) NAND and NOR D) EXOR and EXNOR.

A + AB + A =

!§§|) AB             B) A-r B        C) A             D) O.       (04 Marks)

i) Implement Y=ABCD using two input NAND gates

Simplify Y = (A + B) (a + c) (b + c).                                                                                (08 Ma/ks)

ith a circuit, explain the working principle of parallel binary adder. (08 Marks)