RGPV Exams Questions Papers 3rd SEM Dec 2006 Electronics
RGTU B.E. (Third semester) EXAMINATION, DEC, 2006
(Common for EC/EE/IP Engg.)
(ELECTRONICS – EE/EC/EX-304)
Note. (i) Answer all question.
(ii) Total six question are to be attempted.
(iii) There is internal choice within each question.
(iv) Answer off all objective question should be at one place only.
(vi) Assume suitable missing/misprint data if necessary.
1. (a) (i) The concentrations of minority carriers close to the junction in forward biased p-n junction.
(a) are same ads the concentration without biasing.
(b) are less than the concentration without biasing.
© are more than the concentration without biasing.
(d) is less than the concentration without biasing in the p-region and more than the concentration
without biasing in the n-region
(ii) A BJT used as a switch, switches between
(i) Cut-off and active region
(ii) Cut-off and saturation region
(iii) Active and saturation region
(iv) Different operating point in the active region.
(iii) For an n-channel enhancement mode MOSFET , the drain current
(a) Decreases with increases in the gate current
(b) Increases with increase in gate voltage
© Is independent of gate voltage.
(d) Decreases with increases in drain voltage.
(B) (i) Which of the folowinng is not an advantage of negative feedback?
(a) Increases the gain of an amplifier
(b) Increases in bandwidth
© Reducing non liner distortion
(d) Improving the input and output impedances
(ii) Oscillator used for generation of low frequency signals upto about 100 kZ is
(a) Colpits oscillator
(b) RC phase shift oscillator
© Hartley oscillator
(d) Crystal oscillator
(iii) Collector current of a class A amplifier flows
(a) for 360o (b) for 180o
© more than 180o and less tan 360o
(d) For 90o
(C ) (i) The pulse width of a monostable multavibrator can be controlled by :
(a) The amplitude of the trigger pulse
(b) The width of the trigger pulse
(c ) The timing resistor and capacitor
(d) Any of the above
(ii) in Darlington pair , you
(a) add the individual ß’ s to get the overall ß
(b) multiply the individual ß’ s to get the overall ß
( c) Subtract the individual ß’ s to get the overall ß
(d) none of the above
(iii) When the BJT is turned from ON to OFF , the transistor comes to the off state.
(a) as soon as the input signal is reserved
(b) as soon as the power supply is switched off
(c ) After the excess charge stored in the base region is removed.
(d) After the input signal is removed
(D) (i) Ideal OP-AMP has a CMRR
(a) low (b) high
(c ) zero (d) infinity
(ii) The gain of a non –inverting amplifier having Rf = 2k and R1 =k will be :
(a) 1 (b) 2
( c) 3 (d) 4
(iii) A 555 timer can be used as :
(a) an stable multavibrator only
(b) a monostable multavibrator only
(c ) a frequency divider only
(d) any of the above
(E) Thrusters are :
(a) three layer semiconductor devices
(b) four layer semiconductor devices
(c ) five layer semiconductor devices
(d) any of the above
(ii) To latch a SCR
(a) a positive trigger should hit the gate input
(b) the current should be reduced below holding current
(c ) none of the above
(iii) Which of the following can work as oscillator ?
( c) Both of the above
2. (a) Discuss the affect of temperature on zener and avalanche breakdown
(b) Draw the circuit diagram of an NPN transistor CE configuration and describe the input and output
characteristics . also define active saturation and cut-off region of CE transistor .
(a) Compare the following parameter of the three BJT configuration :
(i) Voltage gain (ii) Current gain
(iii) Input impedance (iv) Output impedance
(b) Draw the D.C. load line for the circuit given in figure. Also show the Q point .
3. (a) What is the relation between gain and feedback Af and that without feedback A ? Define negative
and positive feedback .
(b) Sketch the circuit of phase shift oscillator. Explain its working determine the frequency of
(A) State the explain barkhausen ‘criterion for sustained oscillator .
(b) Explain the working of class-b push-pull amplifier with the help of circuit diagram. Show that its
maximum conversion efficiency is 78.5%
4. (a) Diffrencaite between clippers and clampers
(b) Explain with the help of circuit diagram , how darlington connection method is used to increase the
input resistances of a transistor amplifier . Also discuss how darlington circuit can be improved by
adding bootstrapping circuit ?
(a) Explain ‘Turn on’ and ‘turn off’ timings of BJT . also explain why CE configuration is commonly
employed for transistor as a switch .
(b) Explain the working of a stable multavibrator with te help of circuit diagram and wave forms. Also
give its application.
5. (a) What is an OP-AMP ? list all the ideal characteristics of OP-AMP .
(b) Draw the circuit and explain how :
(i) Op-Amp can be used as an integrator
(ii) Op-Amp can be used as a differentiator
Also draw input and output wave forms.
(a) Explain CMRR and slew rate regarding OP-AMP
(b) Draw the circuit of monostable multavibrator using 555 timer . Explain its operation and sketch the
relevant wave forms.
6. (a) Write a short about constructions of SCR
(b) Draw and explain v-1 characteristic of SCR . also explain different method for starting on SCR .
(a) Explain the working of chopper circuit .
(b)What is meant by Gate ON and OFF times ? Explain in detail turn OFF and turn ON mechanism in SCR .