Elec Circuits & Comm. Fundamentals - May 2013

Computer Engineering (Semester 3)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks. 1(a) Explain the purpose of thin and lightly doped base region of BJT structure (5 marks) 1(b) List the characteristic feature of 555 timer (5 marks) 1(c ) Design a circuit with OP-AMP to produce the o/p Vo given by- Vo=(Vs1+Vs3)-(Vs2+Vs4)(5 marks) 1(d) Justify how FET can be used as variable resistor, constant source and constant voltage source(5 marks) 2(a) Explain the graphical determination of h-parameters using characteristic curve of CE amplifier (10 marks) 2(b) Determine the following for the circuit shown in the figure- (i) IBQ (ii) ICQ (iii) VCEQ (iv) VCQ (v) VBQ (vi) VEQ Use exact and approximate analysis for the same.

(10 marks) 3(a) Derive equation for Zi, Zo,Av for common source configuration using voltage divider network (with unbypassed RE) (10 marks) 3(b) Calculate the voltage gain, input and output impedance for the circuit shown below

(10 marks) 4(a) Explain any two applications of mono-stable multi-vibrator.(10 marks) 4(b) Design a regulator LM 723 for V0=9V and Io=3Amp.(10 marks) 5(a) Explain the D/A convertor using binary weighted resistor.(10 marks) 5(b) Explain how an op-amp can be used as (i) Integrator(ii) Differentiator(10 marks) 6(a) Explain instrumental amplifier with 3 op-amps.(10 marks) 6(b) Using IC 555 design A-stable multi-vibrator for output frequency at 5KHz and duty cycle of 70%. Draw the related waveforms(10 marks) 7(a) Virtual ground concept of Op-amp(5 marks) 7(b) Inverting Schmitt trigger(5 marks) 7(c ) Properties of ideal Op-amp(5 marks) 7(d) PLL(5 marks) 7(e ) Zero crossing detector(5 marks)