III/IV B.Tech Degree Examinations, April 2014
First Semester
Electronic Circuits II
Time : 3 hours
Maximum Marks : 60
Answer question No.1 Compulsory
Answer ONE question from each Unit
1. Briefly explain following [12 x 1 = 12M]
a) Given transistor I_{c} = 26 m A. Find the value of g_{m} at room temperature.
b) What is the relation between f_{β} and f_{T}?
c) What is the value of CE short circuit current gain at signal frequency f = f_{β}?
d) Write the formula for emitter diffusion capacitance C_{e} in terms of g_{m} and f_{T}.
e) Draw the small signal model of FET
f) What are the advantages of SMPS over conventional power supplies?
g) Compare series and shunt voltage regulators.
h) Write the formula for overall upper 3 dB frequency of n cascaded stages.
i) In low frequency region the amplifier acts as which filter?
j) Write the formula for bandwidth of parallel resonant circuit.
k) Mention the applications of Tuned amplifiers.
l) Draw the frequency response of double tuned amplifier.
UNIT - I [1 x 12 = 12M]
2. a) Draw the circuit of hybrid-π CE transistor model and define the components.
2. b) The following low-frequency parameters are known for a given transistor at I_{c} = 10 m A, V_{ce} = 10 V at room temperature. h_{ie} = 500 ohms, h_{oe} = 4x10^{-5} A/V, h_{fe} = 100 and h_{re} = 10^{-4} at the same operating point, f_{T} = 50 M Hz and C_{ob} = 3 pF. Compute the values of all the hybrid-π parameters. (OR)
3. a) Derive the expression for CE current gain with resistive load using equivalent circuit.
3. b) Given the germanium p-n-p transistor whose base width is 10^{-4} cm. At room temperature and for dc emitter current of 2 mA, find the emitter diffusion capacitance and f_{T}.
UNIT - II [1 x 12 = 12M]
4. a) Draw the equivalent circuit of common source (CS) amplifier at high frequencies and Explain.
4. b) Derive the expressions for voltage gain, input admittance and input capacitance of CS amplifier at high frequencies. (OR)
5. a) Explain the operation of SMPS with neat block diagram.
5. b) Explain design of Shunt regulator with example.
UNIT - III [1 x 12 = 12M]
6. a) Derive the low frequency response and high-frequency response of RC-coupled amplifier with expressions and graph.
6. b) Explain distortions in amplifiers. (OR)
7. a) Derive the expressions for over all band pass of cascaded stages.
7. b) Three identical cascaded stages have individual upper 3 dB frequency of 100 kHz and lower 3 dB frequency of 100 Hz. What is overall f_{H} and f_{L}?
UNIT - IV [1 x 12 = 12M]
8. a) Draw the Parallel-Resonant circuit and explain with Impedance function and bandwidth.
8. b) Draw the circuit of single tuned amplifier and explain its operation with frequency response. (OR)
9. a) Draw the circuit of double tuned transformer coupled amplifier and explain its operation with frequency response.
9. b) Draw the circuit of tuned secondary amplifier and explain its operation.