Analog Electronic Circuits - Jun 2015

Electronics & Communication (Semester 3)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) State and explain the various resistance levels of the semiconductor diode.(6 marks) 1 (b) Explain the working of a full wave centre tapped rectifier. Also determine ripple factor, efficiency and voltage regulation.(10 marks) 1 (c) Design a suitable circuit represented by the box shown below, which has the input and output waveforms as indicated. (4 marks) 2 (a) Name different biasing methods of transistor. With circuit diagram analyse the fixed bias circuit, with effect of variation in I_B, R_C and V_CC on Q, point of the load line.(10 marks) 2 (b) Explain the circuit of transistor switch being used as an inverter.(4 marks) 2 (c) In a voltage divider bias circuit of BJT. V_CC=20 V, R_C=10 KΩ, RE=1.5 kΩ, R₁=40 kΩ, R₂=4 kΩ. Assume silicon transistor β=150. Find I_C, V_CE and I_C(sat) using exact analysis.(6 marks) 3 (a) Define h-parameters and hence derive h-parameters model of CE-BIT.(6 marks) 3 (b) Explain with a neat circuit diagram of emitter configuration. Justify how voltage gain is nearly equal to one.(6 marks) 3 (c) For the circuit shown below determine V_CC, if A_V=160 and r₀=100 kΩ. Take β=100. (8 marks) 4 (a) Draw the single stage RC coupled BJT amplifier and discuss the effect of (low frequency response): i) Input capacitance C_b ii) output capacitance C_C and iii) Emitter by pass capacitance C_e on frequency response.(5 marks) 4 (b) Prove that miller effect of input capacitance C_Mi=(1-A_v) Cf and output capacitance $$ C_{M0} = \left ( 1- \dfrac {1} {A_v} \right ) C_f. $$(10 marks) 4 (c) It is desired that the voltage gain of an RC - coupled amplifier at 60Hz should not decrease by more than 10% from its mid bond value. Calculate:
i) the lower 3 dB frequency
ii) the required C if R=2000 Ω.(5 marks) 5 (a) Derive expression for Z_i and A_i for a Darlington emitter follower circuit.(10 marks) 5 (b) Mention the types of feedback connections. Draw their block diagrams indicating input and output signal.(6 marks) 5 (c) List the general characteristics of a negative feedback amplifier and write its advantages.(4 marks) 6 (a) With a neat circuit diagram, explain the operation of a transformer coupled class A power amplifier.(7 marks) 6 (b) Explain the operation of class B push-pull amplifier and derive its conversion efficiency.(8 marks) 6 (c) The following distortion reading are available for a power amplifier:
D₂=0.2, D₃=0.02, D₄=0.06 with <mark>R₁ =3.3A </mark> and R_C=4Ω Calculate:
i) the THD
ii) the fundamental power component
iii) the total power.(5 marks) 7 (a) Explain the working of Wien bridge oscillator.(7 marks) 7 (b) With a neat circuit diagram, explain the operation of BJT Colpitt's oscillator.(6 marks) 7 (c) A crystal has the following parameter L=0.334 H, C_M=1 pF, C=0.065 and R=5.5 kΩ. Calculate the series resonant frequency, parallel resonant frequency and find Q of the crystal.(7 marks) 8 (a) Draw the JFET common drain configuration (source - follower) circuit. Derive Z_i, Z₀ and A_v using small signal model. Write its characteristics.(10 marks) 8 (b) Compare JFET and MOSFET.(3 marks) 8 (c) For the JFET common drain configuration shown below. Given I_DSS=10 mA, V_p=-5V, r_d=40 kΩ, V_GSQ=-2.85V i) calculate Z_i and Z_o ii) Calculate A_v iii) find V₀ if V_i=20 mV (p-p). (7 marks)