C 830045 Total Pages:4

impedance (ii) current gain (iii) voltage gain (5)

b) Why the gate junction of FET is always reverse biased? List the parameters of JFET from

characteristics. (5)
11. a) Explain any compensation technique adopted in transistor amplifier for reducing the drift
of operating point. (5)

b) The datasheet of an N-channel JFET gives the following details Ips; = 9 mA and pinch
off voltage of -4.5V i) At what value of Ves will [ந be equal to 3 mA?
ii) What is its gm at this Ip? (5)
PART ^
Answer any 2 questions. Each question carries 10 marks.
12. a) A differential amplifier has inputs Vs; =10mV and Vs2= 9mV. It has differential mode
gain of 60 dB and a CMRR of 80 dB. Find the percentage error in output and error
voltage. (2)
b) State the Barkhausen criterion for sinusoidal oscillators and why this must be fulfilled to
sustain oscillations? (3)
€) Fora class 8 power amplifier using a supply of Vcc =12V and driving a load of 8Q,
Determine maximum load power. DC input power and collector efficiency. (5)
13. a) An amplifier with negative feedback has a voltage gain of 100. It is found that without
feedback an input signal of 50mV_ 18 required to produce a given output, whereas with

feedback, the input signal must be 0.6V for same output. Calculate the value of A and 0.

(5)
b) Show how piezo-electric crystals are employed for oscillator stabilization. (3)
c) Acrystal has the following parameters 1, ಎ 0.33H,Ci = 0.065pF,C2 = 1.0pF and
R=5.5KQ. Determine series resonant frequency and ಛಿ factor of the crystal. (2)

14. a) Compare the merits and demerits of different types of inter stage coupling in amplifiers
(3)
b) What is cross over distortion? Why most power amplifiers used in practice are designed
to operate in class AB stage? (2)
c) An inverting op-amp with slew rate 0.5V/usec is shown in the figure. Determine i) closed

loop voltage gain ii) input impedance of the circuit iii) Maximum operating frequency

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