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B3D057 Total pages:2

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
THIRD SEMESTER B.TECH DEGREE EXAMINATION, JANUARY 2017 Course
Code: EC205
Course Name: ELECTRONIC CIRCUITS (AE, EC)

Max. Marks: 100 Duration: 3 Hours

1.

PART A
Question is 1 COMPULSORY and Answer EITHER Question 2 OR Question 3 Each
Full Question Carries 15 marks.

a) Define the THREE stability factors of Common Emitter amplifier and derive
expression for the Current stability factor of a potential divider bias CE amplifier
circuit. (8)
b) A Common Base amplifier is driven by a voltage source of internal resistance
60൮. The load resistance is 20KQ. The transistor has 19 = 2262, hw» = 0.0003, hm = -
0.98 and hob= 0.5uA/V. Compute the current gain At, input resistance Ri, voltage gain
Avy, overall voltage gain Avs, overall current gain ഷം (considering the source resistance
also), and operating power gain Ap. (7)
a) An ideal 1/15 pulse from a pulse generator is fed to an amplifier. Calculate and plot
the output waveform with a rise time of the capacitor 2.2 RC. The upper 3dB
frequency is 0.1 MHz. (7)
b) How amplifiers are classified based on their Q-points? Explain showing the
positions of the Q-points on the respective load lines and _ current transfer
characteristic curves for at least THREE types of classes. Also compare their merits
and demerits. (8)
a) Define the small signal hybrid parameters of a Common Emitter configuration.
Show how to determine their values from the characteristics. (8)
b) Draw the circuit of a two-stage RC coupled amplifier. Derive expressions for its
effective lower cut-off frequency and effective upper cut-off frequency. If the
individual stages are having 7. = 20 Hz and fy = 200 kHz, calculate the respective
values for the cascaded two-stage. (7)

PART B

Question 4 is COMPULSORY and Answer EITHER Question 5 OR Question 6 Each Full Question

Carries 15 marks.

4. a) What are the physical origins of resistances in the high frequency hybrid 7 model ofa

CE transistor amplifier? Explain the different parameters in the hybrid 7 circuit.

(7)
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