# RGPV Exams Questions Papers 3rd SEM June 2005 Electronics

RGTU B.E. (Third semester) EXAMINATION, JUNE, 2005

(Common for EC/EE/IP Engg.)

(ELECTRONICS – EE/EC/EX-304)

Note:      Attempt any five questions.  All question carry equal marks.

1. (A) Define the following term for a P-N junction diode :

(i) Diffusion capacitance    (ii)  Transition capacitance

(iii) Static and dynamic resistance

(b)  A silicon diode operators at a forward voltage of 0.4 V.  Calculate the factor by which the current will

be multiplied when the temperature is increased from 25 to 150oC.

©    Sketch the amp. Characteristics of tunnel diode . Explain the negative resistance in tunnel  diode .

2. (a) For a full wave rectifier shown in ahed fig. 1, Calculate V d.c. , IIdiode and PIV if Np : Ns=3 : 1,V­in 155

Va.c. with 50 Hz.

(b) For the circuit shown in fig.2 , determine the minimum value of Ib to saturate the transistor.

3. (a) In the fig.3 , V as =-1 V, calculate VG, VS, ID if IDSS = 10 Ma, VGS  OFF  =_ 4v.

(b)  Draw and discuss the characteristics of P-channel depletion type MOSFET.

4.  (a)  In Fig. 4, V1 =2 V and V2 = 7.5 V draw the output waveform assume both diodes to be Si diode.

(b)  Design an astable multavibrator for the following specifications:

Vcc = 10 V,  ICsat  = 5mA , ?= 50, f=3  kHz and duty cycle = 50%.

5. (a) Determine the type of feedback and draw the equivalent circuit for determination of open loop

gain for the circuit shown in Fig. 5.

(b)  An amplifier has a gain G=5 provide a feedback to this network such that the gain of the amplifier

with feedback G becomes 100. If G is increased by 2% What is the percentage change in Gp ?

6. (a) Find C such that the circuit in fig. 6 oscillates.

(b) What is the maximum amount of phase shift provided by single RC section shown in fig. 7. Can an RC

circuit phase shift oscillator be made using two such section?

7.  (a)  For the circuit shown in fig. 8. Determine the gain Vo/  V i.  Assume om-amp to be ideal.

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(b) Design an op-amp . circuit containing three inputs V1,  V2 and  V3  with the output Vout  equal to the

average of these inputs . How many op-amps will be needed if polarity is of no concern ?

8. Write short notes on any two of the following :

(a)  Turn ON and OFF mechanism of SCR

(ii)   Single phase controlled rectifier with resistive load.

(iii)  Solid state firing circuit using  UJTS .