(Effective from the admitted batch of 2006-2007)
Time: three hours maximum: 70 marks
All questions carry equal marks
Answer any five questions and question no.1 is compulsory
1. Answer the fallowing.
(a) What is meant by charge density?
(b) Write the diffusion and continuity equations.
(c) What is zener breakdown?
(d) Compare the characteristics of silicon and a germanium diode and determine which you would prefer to use for most practical applications.
(e) State different parameters of FET.
(f) State the difference between drift and diffusion current.
(g) What is the effect of coupling capacitor in amplifiers?
2. (a)what is meant by the minority carrier storage time of a diode?
(b)a zener voltage regulator circuit is to maintain constant voltage at 60v,over a current range from 5 to 50 mA. The input supply voltage is 200V. deter mine the value of resistance R to be connected in the circuit, for voltage regulation from load current IL=0ma to IL max , the possible value of IL what is the value of IL max?
3. (a) what is the cause of surge in rectifier circuits using capacitor filter. How is the current limited?
(b) in a full wave rectifier the required dc voltage is 9v and the diode drop is 0.8v calculate ac rms input voltage required in case of bridge rectifier circuit and center tapped full wave rectifier circuirt.
(c) Derive the expression for the ripple factor of half wave rectifier and full wave rectifier.
4. (a) what are the different configurations of BJT? Explain.
(b) Define ICBO and ICEO.
(c) What is the order of magnitude of ICBO for Si transistor and Ge transistor? How does ICBO vary with temperature?
5. (a) define the different parameters of FET.
(b) What are special semiconductor devices?give explanation for any two diodes.
6. (a) define the stability factor ,S’,S” and what is the need of this in BJT circuits.
(b) Draw the circuit diagram of a self bias BJT circuit and explain how to determine the value of R1, R2.
7. Compare transistor amplifier configurations related to A1, AV, input resistance R1and R2.
(b)for a CE amplifier if R2=RS=1000 and hie=1100,hre=50,hoe=25*10^-6 a/v find Ai Ri Av A vs AIS .
8. (a)with neat sketches explain the cut off region, active region and saturation region of a transistor out put characteristics
(b) Write about the phenomena of reach through in a transistor.
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