VTU Previous Question Papers BE EC 3rd Semester
Electronic Circuits January 2007
Note : 1, Answer any FIVE full questions.
2.Assume missing data suitably.
1 a. With a neat diagram explain the constructional feature of CRT and also explain the focusing scheme used in it.
b. Derive an equation for diffusion capacitance of P-N junction diode.
c. Distinguish between ideal and practical diodes. Draw piece-wire linear characteristic and explain.
2 a. Draw the circuit diagram of a Bridge rectifier with capacitor filter and also derive the expression for ripple factor and rectifier efficiency.
b. Explain the working of a double ended clipper using ideal diodes. Give its transfer characteristics.
c. Explain the tunneling phenomenon in tunnel diodes. Draw its V-I characteristics
3 a. Discuss the causes for bias instability in a transistor.
b. Derive an equation for the stability factor S for a C.E. self bias circuit.
c. Discuss different types of bias compensation technique used in the transistor circuits.
4 a. Using approximate h-parameter model for the transistor, obtain expressions for Z„ Zo, Av> Ai for a C.E self bias amplifier with un bypassed Re.
b. For the circuit shown in the Fig. 4(b) find, Rc, Rb> Re, Vce and Vb
5 a. Write the hybrid-Tt model of BJT and briefly explain the various parameters of the model.
b. Draw the circuit of a bootstrapped emitter follower and explain how it gives higher input impedance than emitter follower.
c. The cutoff frequencies of a transistor amplifier are fi – 500 Hz and f2 = 400 kHz. The midband voltage gain is 80. Find the voltage gain at 250 Hz.
6 a. For the emitter follower network of Fig. 6(a), determine : i) re ii) Zj iii) Z0 iv) Av v) Aj Also derive the equations for Zj, Z0, Av and Ai
b. Explain with relevant sketches how power amplifiers are classified. Derive the expression for the conversion efficiency of a class B push pull amplifier.
7 a. With the circuit diagram explain the working principle of a shunt and series voltage regulator. Also obtain the expression for the regulated output voltage.
b. What is switching regulator? Explain step-down type of switching regulator with a neat block diagram.
8 Write short notes on the following :
a. Photo diodes
b. Ebbers Mol model of PNP transistor
c. Voltage doublers
d. Class A power amplifier.