# EC2205 Electronic Circuits I May June 2012 Question Paper

Anna University Chennai
Question Paper Code:
B.E./B.Tech. DEGREE EXAMINATION, May June 2012
Third  Semester
Electronics and Communication Engineering
EC2205 Electronic Circuits I
(Common to Medical Electronics Engineering)
(Regulations 2008)
Time: Three Hours
Maximum: 100 Marks

Note: New Subject Code in R-2013 is EC6304

Part A (10 x 2 = 20 Marks)

1. Define Stability Factor
2. What are the different methods of biasing JFET?
3. Write the voltage gain equation for CE configuration including source resistance
4. What is the need of constant current circuit in differential amplifier?
5. Why are h parameters not used at high frequencies?
6. How is the high frequency gain of an amplifier limited?
7. What is IC biasing Current steering circuit using MOSFET?
8. Does this "enhancement load" resemble a resistor?
9. Why FET is called as a voltage controlled device?
10. Write the applications of MOSFET.
Part B (5 x 16 = 80 Marks)
11. (a) Explain fixed biasing in BJT and FET. Explain the procedure for locating operating point on the characteristic curves.
OR
(b) Draw a voltage divider bias BJT network. Derive expressions for ICQ and VCEQ and describe the method of drawing the dc load line on the output characteristics of transistor.

12. (a) (i) A CC amplifier is fed with the voltage source Vs of internal resistance Rs = 800â„¦. The load resistance RL = 1600â„¦. The CE hybrid parameters are hie = 1000â„¦;  hre = 2.2 x 10-4;  hfe = 55; hoe = 23 ÂµA/V. Compute voltage gain, current gain, input resistance, output resistance using approximate analysis. (8 Marks)
(ii) Explain the boot strapped Darlington emitter follower with circuit diagram. (8 Marks)
OR
(b) Draw the small signal hybrid model of CE amplifier and derive the expression for its AI, AV, RI, RO.

13. (a) (i) Define alpha cutoff frequency. (4 Marks)
(ii) Draw the high frequency hybrid Ï€ model for a transistor in the CE configuration and explain the significance of each component. (12 Marks)
OR
(b) Using hybrid Ï€ model of a CE amplifier derive the expression for its short circuit gain. (16 Marks)

14. (a) Derive the expression of the differential-mode voltage gain, common mode voltage gain and CMRR for a MOSFET differential amplifier.
OR
(b) Explain in detail the MOSFET amplifiers with enhancement load and depletion load

15. (a) With the neat sketch explain the principle of operation of cascode amplifier and also derive an expression for its performance measures?
OR
(b) A dc analysis of the source-follower network of the following figure will result in VGSQ= -2.86 V and IDQ = - 4.56 mA.
(a) Determining gm.
(b) Find rd.
(c) Determine Zi.
(d) Calculate Zo with and without rd. Compare results.
(e) Determine Av with and without rd. Compare results.