# VTU Previous Year Question Papers BE EC Third Semester

# Analog Electronic Circuits December 2010

**Note: Answer any FIVE full questions, selecting at least TWO Questions from each of Part -A and Part-B.**

**PART-A**

1 a. What is an equivalent circuit of a device? Explain the different equivalent circuits for semiconductor diode.

b. Analyse the circuit shown below, Fig. Ql(b), and draw the output waveform. Assume V_{r} – 0,7V.

c. Write a suitable circuit to get the following transfer characteristics fig. Ql (c), and explain its working.

2 a. Find I_{c} and V_{CE} for the circuit shown, Fig. Q2(a).

b. Find the coordinates of the Q point and locate it on the dc load line for the voltage divider configuration. Given V_{c}c = 16V, Ri (upper resistor) = 62 kQ., R_{2} = 9.1 k£l, Rc = 3.9kQ , Re – 0.68kQ and P = 80. The coupling capacitors are 10µF each. Also find Vc, V_{E} and V_{B}.

c. Define turn ON time and turn OFF time of a transistor. Design a transistor inverter if Vcc ^{=} 10V, I_{c} = 10mA and p = 250. Assume input to be a pulse of amplitude 10V.

3 a. What is bias stabilization? Explain. Derive an expression for S(Ico) and S(V_{BE}) for fixed bias configuration.

b. For an emitter bias circuit (capacitor is bypassed), determine r_{e}, Zj, Z_{0} and A_{v}. Given R_{b} = 470 kH , R_{c} = 2.2kQ, V_{cc} = 20V, R_{E} = 0.56kQ , C_{E} = 10µF , p = 120 , r_{0} = 40kQ , C_{c} = lO^F.

c. Determine i) the common logarithm of the number 2.2x 10^{3}. ii) the power gain in decibels for P_{0} = 100 m watts ,P_{i} = 5m watts.

4 a.The transistor is connected as a CE amplifier. Determine Z_{c}, Z_{0}, Ai and Ay using complete hybrid model.

b. Discuss the low frequency and high frequency response of a RC coupled amplifier.

**PART-B**

5 a. For the circuit of fig. Q5(a), calculate the dc bias voltage Ve-

b. With a block diagram, explain the difference between voltage series and voltage shunt feedback.

c. Using the block diagram approach, derive an expression for A_{f} and Z_{0}f for current series feedback amplifier.

6 a. With a neat circuit diagram, explain the operation of a transformer coupled class A power amplifier.

b. For a class B amplifier with Vcc ~ 25V driving an 80 load, determine i) maximum I/P power ii) maximum O/P power iii) maximum circuit efficiency.

c. Calculate the second harmonic distortion for an O/P waveform having measured values of

7 a. With a neat circuit diagram, explain the working principle of RC phase shift oscillator, with relevant equations.

b. What are the tuned oscillators? Explain any one type of tuned oscillator.

8 a. Define g_{m} and rd of field effect transistor. Explain the procedure to determine the above values graphically.

b. Write the ac equivalent circuit for voltage divider JFET configuration and determine Zj, Z_{0} and A_{v}.

c. Differentiate between enhancement and depletion MOSFET.

3rd semester vtu previous year question papers of Analog Electronic circuits 2011,2012