1. ELCT 371: Electronics Pre-Req: CSCE 211, ELCT 222 Dr. Goutam Koley Room 3A12, 777- 3469, koley@engr.sc.edukoley@engr.sc.edu Lecture Hours: Tue & Thurs 12.30 – 1:45 AM SWGN 2A15 Office Hours: Tue and Thurs 2.30 – 3.30, and by appointment 1

2. Objective Objective: To learn the basics of analog circuit design and analysis Text book: Electronics, by Allan R. Hambley, 2 nd Edition, Prentice Hall, Upper Saddle River, NJ 07458, 2000 ISBN # 0136919820 2

3. Schedule and Grading Grading:Homeworks:(6) 12 % Pop Quiz(4) 16 % Midterms:(2) 32 % Final:(1) 40 % Class: Jan 12 – April 22; 28 lecture days. Final Exam: Wednesday, April 28, 2010; at 2.00 pm. Grades (Total 100 points): A: 90 - 100B+ : 85 – 90B: 80 – 84C+ : 75 - 79 C: 70 – 74D+: 65 – 69D: 60 – 64F: <60 All grades will be normalized. The highest overall individual score (out of 100) will be made 100, and all the others will be multiplied by the ratio before assigning the final grade. If there are confusions regarding any grading please bring it to my attention immediately after the grading is done. Otherwise, you may not get benefit of any corrections. 3

4. Some reminders… Eating or drinking in class is NOT preferable. However, if you absolutely have to, you must not disturb others. Do not enter the class if you are more than 15 minutes late, without very valid reasons No retake of exams/tests permitted unless you let me know prior to the test/exam and have valid reasons PLEASE ADHERE TO THE UNIVERSITY OF SOUTH CAROLINA HONOR CODE (No cheating in any form!!!) 4

5. An ideal amplifier produces an output signal with a larger amplitude while maintaining the same waveshape 1.4 Basic Amplifier Concepts input voltage output voltage voltage gain Microphone 1 mV Amplifier A v =10,000 Loudspeaker 10 V output Fig. 1.15 5

6. Inverting and Noninverting Amplifiers: 1.4 Basic Amplifier Concepts Inverting Amplifier is a negative number Noninverting Amplifier is a positive number Fig. 1.16 6

7. The Voltage-Amplifier Model 1.4 Basic Amplifier Concepts Fig. 1.17 v s is the source voltage R s is the source resistance R L is the load resistance R o is the output resistance of the amplifier R i is the input resistance of the amplifier R i is the equivalent resistance looking into the input terminals of the amplifier and R o is the same looking into the output terminals Input impedance Z i for a typical oscilloscope is a 1 M  resistance in parallel with 47 pF capacitance A vo is the open circuit voltage gain 7

8. The Voltage-Amplifier Model Real amplifiers cannot deliver a fixed voltage to an arbitrary load resistance Output voltage changes with load resistance - Higher for larger R L and lower for smaller R L The amplifier output resistance accounts for the reduction in output voltage 1.4 Basic Amplifier Concepts A vo is the open circuit voltage gain of the amplifier, meaning the load is infinite. Thus there is no drop across the resistances, and v 0 = A vo v i Actual amplifier voltage gain A v =v 0 /v i is always smaller than A vo Fig. 1.17 8

9. 1.4 Basic Amplifier Concepts Fig. 1.17 Current Gain is the voltage gain with the load resistor connected. Note that A v is smaller than A v0 9

10. Power Gain Assuming the input impedance and load impedance are purely resistive, the average power is the product of the rms current and rms voltage. 1.4 Basic Amplifier Concepts Fig. 1.17 10

11. Example 1.1: Find voltage gain, current gain, and power gain for the circuit below 1.4 Basic Amplifier Concepts 11 Fig. 1.18

12. 1.5 Cascaded Amplifiers Fig. 1.19 12

13. 1.5 Cascaded Amplifiers Fig. 1.20 Example 1.2 Analysis of a Cascaded Amplifier 13

14. 1.5 Cascaded Amplifiers 14 Power gain:

15. Simplified Models for Cascaded Amplifier Stages Example 1.3 Determining the Overall Model of a Cascaded Amplifier Fig. 1.20 1.5 Cascaded Amplifiers 15

16. Fig. 1.21 Simplified model for the cascaded amplifiers of Fig. 1.20 1.5 Cascaded Amplifiers Question: Who provides the power to amplify the input signal? 16

17. Power supply delivers current from several dc voltages to the amplifier The total power supplied is the sum of the powers supplied by each voltage source 1.6 Power Supplies and Efficiency Fig. 1.22 17

18. Fig. 1.23 Here, P i = power entering the amplifier from the signal source P s = power from the power supply P 0 = output power P d = dissipated power 1.6 Power Supplies and Efficiency 18

19. Power Efficiency: Example 1.4 Determining the Power Efficiency of an Amplifier Fig. 1.24 1.6 Power Supplies and Efficiency 19

20. Fig. 1.24 1.6 Power Supplies and Efficiency 20

21. Power gain is often expressed in decibels (dB) as An attenuator having the output power smaller than the input power, has a negative decibel gain The overall gain for cascaded amplifiers is the product of the power gains of the individual amplifiers Power gain can be computed from voltage gain, input resistance and output resistance as given by equation (1.6) 1.7 Decibel Notation ; [expressed in decibels] Finally, 21

22. [Converted to decibels] Therefore, Voltage and Current Gains Expressed in Decibels [Voltage gain converted to decibels] [Current gain converted to decibels] 1.7 Decibel Notation 22