Circuits and Analog Electronics 电路与模拟电子技术

1. 10 级计算机科学 2＋2 Circuits and Analog Electronics 电路与模拟电子技术 Prof. Li Chen, School of Information Science and Technology, Sun Yat-sen University 中山大学信息科学与技术学院 陈立副教授 Email: chenli55@mail.sysu.edu.cn

2. Circuits and Analog Electronics • References： • W. H. Hayt, Jr., J. E. Kemmerly and S. M. Durbin, Engineering Circuit Analysis, McGraw-Hill, 2005, ISBN 978-7-121-01667-7. • R. L. Boylestad and L. Nashelsky, Electronic Devices and Circuit Theory, Pearson Education, 2007, ISBN 978-7-121-04396-3. • 高玉良, 电路与模拟电子技术, 高教出版社, 2004, ISBN 7-04-014536-7.

3. Circuits and Analog Electronics • Handouts available at: • sist.sysu.edu.cn/~chenli • References： • W. H. Hayt, Jr., J. E. Kemmerly and S. M. Durbin, Engineering Circuit Analysis, McGraw-Hill, 2005, ISBN 978-7-121-01667-7. • R. L. Boylestad and L. Nashelsky, Electronic Devices and Circuit Theory, Pearson Education, 2007, ISBN 978-7-121-04396-3. • 高玉良, 电路与模拟电子技术, 高教出版社, 2004, ISBN 7-04-014536-7.

4. Teaching Schedule

5. Circuits and Analog Electronics Ch1 Basic Concepts and Laws of Electric Circuits 1.1Basic Concepts and Electric Circuits 1.2Basic Quantities 1.3Circuit Elements 1.4Kirchhoff's Current and Voltage Laws References: Hayt: Ch1, 2, 5; Gao: Ch1;

6. Power Supplies Transmission Loads Circuits Kinescope Antenna • Electrical power conversion and transmission Amplifiers 1.1 Basic Concepts and Electric Circuits • Signal processing and transmission Speaker transmitter

7. 1.1 Basic Concepts and Electric Circuits • Electrical power conversion and transmission

8. Question: What is the current through the bulb? In order to calculate the current, we can replace the bulb with a resistor. R is the only subject of interest, which serves as an abstraction of the bulb. 1.1 Basic Concepts and Electric Circuits Concept of Abstraction Solution:

9. A resistor is a circuit element that transforms the electrical energy (e.g. electricity  heat); Commonly used devices that are modeled as resistors include incandescent, heaters, wires and etc; 1.1 Basic Concepts and Electric Circuits Resistance: R = V/I, 1 =1V/A, ohm; Conductance: G = 1/R = 1A/V, siemens (S); 1S = 1A/V, i(t) = G×v(t); Instantaneous current and voltage at time t; • A circuit consists of sources, resistors, capacitors, inductors and conductors; • Elements are lumped. • Conductors are perfect. Lumped circuit abstraction!

10. Transmitter Receiver 1.1 Basic Concepts and Electric Circuits The AM Radio System • Understanding the AM radio requires knowledge of several concepts • Communications/signal processing (frequency domain analysis) • Electromagnetics (antennas, high-frequency circuits) • Power (batteries, power supplies) • Solid state (miniaturization, low-power electronics)

11. Example 1: The AM audio systemExample 2: The telephone system 1.1 Basic Concepts and Electric Circuits

12. 1.1 Basic Concepts and Electric Circuits The AM Radio System • A signal is a quantity that may vary with time. * Voltage or current in a circuit • * Sound (sinusoidal wave traveling through air) • * Light or radio waves (electromagnetic energy traveling through free space) • The analysis and design of AM radios (and communication systems in general) is usually conducted in the frequency domain using Fourier analysis, which allows us to represent signals as combinations of sinusoids (sines and cosines).

13. High Frequency Low Frequency 1.1 Basic Concepts and Electric Circuits The AM Radio System Frequency is the rate at which a signal oscillates. Duration of the signal T, frequency of the signal f = 1/T.

14. 1.1 Basic Concepts and Electric Circuits The AM Radio System • Visible light is the electromagnetic energy with frequency between 380THz (Terahertz) and 860THz. • Our visual system perceives the frequency of the electromagnetic energy as color: is 460THz, is 570THz, and is 630THz. • An AM radio signal has a frequency of between 500kHz and 1.8MHz. • FM radio and TV uses different frequencies. blue red green • Mathematical analysis of signals in terms of frequency • Most commonly encountered signals can be represented as a Fourier series or a Fourier transform. A Fourier series is a weighted sum of cosines and sines.

15. 1.1 Basic Concepts and Electric Circuits The AM Radio System Fourier Series: A Fourier series decomposes a periodic function (or signal) into the sum of a set of sines and cosines. Given function f(t) with angular frequency ω and period T, its Fourier series can be written as: f(t) = A0 + A1msin(ωt + ψ1) + A2msin(2ωt + ψ2) + ··· =

16. t , k is even. , k is odd. 1.1 Basic Concepts and Electric Circuits Example: Given function during a period: For the example :

17. 1.1 Basic Concepts and Electric Circuits The AM Radio System Example-Fourier Series 1st series + 3rd series 1st series (k = 1) 3rd series (k = 3) • Signals can be represented in terms of their frequency components. • The AM transmitter and receiver are analyzed in terms of their effects on the frequency components signals.

18. The modulator converts the frequency of the input signal from the audio range (0-5kHz) to the carrier frequency of the station (i.e. 605kHz-615kHz) Signal Source Power Amplifier Modulator Antenna freq 610kHz freq 5kHz Frequency domain representation of input 1.1 Basic Concepts and Electric Circuits The AM Radio System Transmitter Block Diagram Modulator Frequency domain representation of output

19. 1.1 Basic Concepts and Electric Circuits The AM Radio System Modulator: Time Domain Input Signal Output Signal

20. A typical AM station broadcasts several kW Up to 50kW-Class I or Class II stations Up to 5kW-Class III station Up to 1kW-Class IV station Typical modulator circuit can provide at most a few mW Power amplifier takes modulator output and increases its magnitude 1.1 Basic Concepts and Electric Circuits The AM Radio System Power Amplifier Antenna The antenna converts a current or a voltage signal to an electromagnetic signal which is radiated through the space.

21. IF RF IF Mixer Amplifier Amplifier Antenna Audio Envelope Amplifier Detector Speaker 1.1 Basic Concepts and Electric Circuits The AM Radio System Receiver Block Diagram

22. The antenna captures electromagnetic energy and converts it to a small voltage or current. In the frequency domain, the antenna output is Desired Signal Undesired Signals frequency 0 Carrier Frequency of desired station 1.1 Basic Concepts and Electric Circuits The AM Radio System Antenna interferences interferences

23. RF Amplifier amplifies small signals from the antenna to voltage levels appropriate for transistor circuits. RF Amplifier also performs as a Bandpass filter for the signal Bandpass filter attenuates the other components outside the frequency range that contains the desired station Desired Signal Undesired Signals 0 frequency Carrier Frequency of desired station 1.1 Basic Concepts and Electric Circuits The AM Radio System RF (Radio Frequency) Amplifier

24. Desired Signal Desired Signal Undesired Signals frequency frequency 0 0 455 kHz 455 kHz The AM Radio System IF (Intermediate Frequency) Mixer • The IF Mixer shifts its input in the frequency domain from the carrier frequency to an intermediate frequency of 455kHz IF Amplifier • The IF amplifier bandpass filters the output of the IF mixer, eliminating all of the undesired signals.

25. Computes the envelope of its input signal Input Signal Output Signal 1.1 Basic Concepts and Electric Circuits The AM Radio System Envelope Detector

26. Amplifies signal from envelope detector Provides power to drive the speaker Inputs Outputs System 1.1 Basic Concepts and Electric Circuits The AM Radio System Audio Amplifier Hierarchical System Models • Modelling at different levels of abstraction • Higher levels of the model describe overall function of the system • Lower levels of the model describe necessary details to implement the system • In the AM receiver, the input is the antenna voltage and the output is the sound energy produced by the speaker. • In EE, a system is an electrical and/or mechanical device, a process, or a mathematical model that relates one or more inputs to one or more outputs.

27. RF IF IF Envelope Audio Amplifier Antenna Amplifier Detector Mixer Amplifier Input Signal AM Receiver Sound Power Supply Speaker 1.1 Basic Concepts and Electric Circuits The AM Radio System Top Level Model Second Level Model

28. Low Level Model Envelope Detector. Half-wave Low-pass Rectifier Filter Circuit Level Model Envelope Detector + + Vin R C Vout - - 1.1 Basic Concepts and Electric Circuits The AM Radio System

29. Standard SI Prefixes 10-12 pico (p) 10-9 nano (n) 10-6 micro () 10-3 milli (m) 103 kilo (k) 106 mega (M) 109 giga (G) 1012 tera (T) 1.2 Basic Quantities Units • Electric charge (q) • in Coulombs (C) • Current (I) • in Amperes (A) • Voltage (V) • in Volts (V) • Energy (W) • in Joules (J) • Power (P) • in Watts (W)

30. Time rate of change of charge Constant current Time varying current • Notation: Current flow represents the flow of positive charge • Alternating versus direct current (AC vs DC) (1 A = 1 C/s) i(t) i(t) Unit t t DC AC 1.2 Basic Quantities Current • A mount of electric charges flowing through the surface per unit time. Time – varying current Steady current

31. P1.1, In the wire electrons moving left to right to create a current of 1 mA. Determine I1 and I2. -2 A 2 A 1.2 Basic Quantities Current Positive versus negative current Positive charge of 2C/s moving Negative charge of -2C/s moving Negative charge of -2C/s moving Positive charge of 2C/s moving or or Ans: I1= -1 mA; I2 = +1 mA. Current is always associatedwith arrows (directions)

32. + – 2 V -2 V + – 1.2 Basic Quantities Voltage(Potential) • Energy per unit charge. • It is an electrical force drives an electric current. Voltage Units: 1 V = 1 J/C Positive versus negative voltage Two “Do Not (DN)” DN +/- of current (I) tell the actual direction of particle’s movement . DN +/- of voltage (V) tell the actual polarity of a certain point .

33. a  a、b, which point’s potential is higher？ b  a  Vab = ? b  1.2 Basic Quantities Voltage (Potential) Example a b +Q from point b to point a get energy，Point a is Positive? or negative ?  

34. c d c´ d´ a b 1.2 Basic Quantities Voltage (Potential) Example I

35. K Open K Close 1.2 Basic Quantities Voltage (Potential) Example Va=? I I

36. 1.2 Basic Quantities Example I I

37. Rate of change of energy i(t) + v(t) – 1.2 Basic Quantities Power • One joules of energy is expanded per second. P = W/t p(t) = v(t) i(t) v(t) is defined as the voltage with positive reference at the same terminal that the current i(t) is entering. • Used to determine the electrical power is being absorbed or supplied • if P is positive (+), power is absorbed • if P is negative (–), power is supplied

38. 1.2 Basic Quantities Power Example 2A – + + + Power is supplied. delivered power to external element. Power is absorbed. Power delivered to -5V 5V +5V -5V + – – – 2A Note : 2A Power absorbed . -2A

39. Power absorbed by a resistor: 1.2 Basic Quantities Power

40. - - + + - 5 + I1 I2 I3 + - + - + 1 3 4 - - + 2 + - 1.2 Basic Quantities Power P1.5 Find the power absorbed by each element in the circuit. Supply energy : element 1、3、4 . Absorb energy : element 2、5

41. Open Circuit R= R0 I=0, V=E , P=0 E Short Circuit R=0 R0 R＝0 E 1.2 Basic Quantities

42. I R0 R E 1.2 Basic Quantities Loaded Circuit

43. 1.3 Circuit Elements Key Words: Resistors, Capacitors, Inductors, voltage source, current source

44. Passive elements (cannot generate energy) e.g., resistors, capacitors, inductors, etc. Active elements (capable of generating energy) batteries, generators, etc. Important active elements Independent voltage source Independent current source Dependent voltage source voltage dependent and current dependent Dependent current source voltage dependent and current dependent 1.3 Circuit Elements

45. 1.3 Circuit Elements Resistors • Dissipation Elements v=iR P=vi=Ri2=v2/R >0 ， • v-i relationship i R1 R2 R3 R1 R2 R3 v • Resistors connected in series: • Equivalent Resistance is found by Req= R1 + R2 + R3 + … • Resistors connected in parallel 1/Req=1/R1 + 1/R2 + 1/R3 + …

46. 1.3 Circuit Elements Capacitors • Capacitance occurs when two conductors (plates) are separated by a dielectric (insulator). • Charge on the two conductors creates an electric field that stores energy. • The voltage difference between the two conductors is proportional to the charge: q = C v • The proportionality constant C is called capacitance. • Units of Farads (F) - C/V • 1F= one coulomb of charge of each conductor causes a voltage of one volt across the device. 1F=106F, 1F=106PF

47. i(t) The rest of the circuit + v(t) - Energy stored 1.3 Circuit Elements Capacitors series parallel • store energy in an electric field • v-i relationship vC(t+) = vC(t-) • Capacitors connected in series: • Equivalent capacitance is found by 1/Ceq=1/C1 + 1/C2 + 1/C3 + … • Capacitors connected in parallel Ceq= C1 + C2 + C3 + …

48. i(t) circuit + 0.2F v(t) - v(t) 5V 1s 2s t 1.3 Circuit Elements Capacitors For (1) : P1.7 i(t) 1A 2s t -1A 1s (1)

49. i(t) circuit + 0.2F v(t) - w(t) 2.5J t 2s 1s 1.3 Circuit Elements Capacitors P1.7 For (2) : i(t) 1A 2s t -1A For (1)、(2) : 1s (2)

50. i(t) + circuit L v(t) - Energy stored: 1.3 Circuit Elements Inductors • store energy in a magnetic field that is created by electric passing through it. • v-i relationship iL(t+) = iL(t-) • Inductors connected in series: Leq= L1 + L2 + L3 + … • Inductors connected in parallel: 1/Leq=1/L1 + 1/L2 + 1/L3 + …