전자 회로 1 Lecture 1

1. 전자 회로 1Lecture 1 2009. 03. 임한조 아주대학교 전자공학부 hanjolim@ajou.ac.kr 이 강의 노트는 전자공학부 곽노준 교수께서 08.03에 작성한 것으로 노트제공에 감사드림.

2. Overview • Review of basic electric circuit • Resistor, capacitor, inductor • Current and voltage source (Norton/Thevenin form) • Frequency response (single time constant) • Introduction to Amplifiers • Gain • Transfer characteristics • Introduction to Inverters • Noise margin • Propagation delay • Some materials in this note are from • Lecture notes of Prof. Woodward Yang (Harvard U.) • http://www.deas.harvard.edu/courses/es154 • Lecture notes of Prof. Sang-Bae Kim (Ajou U.) Nojun Kwak

3. Review of Circuit Basics • Some basic circuit elements that will be used extensively in this class. Nojun Kwak

4. Capacitor • Has memory/hysterisis • Terminal relationship • Stores charges on electrodes (parallel plates) • Energy stored in electric field • Capacitance measured in units of Farads (F) • Range of typical values (1pF ~ 1000uF) • Capacitor types • Ceramic (pF) • Mylar (nF) • Electrolytic (uF) • Remember • At LF, C is open circuit • At HF, C is closed circuit Nojun Kwak

5. Inductor • Has memory/hysterisis • Terminal relationship • Energy stored in magnetic field • Inductance measured in units of Henries (H) • Range of typical values (1uH ~ 1H) • Remember • At LF, L is closed circuit • At HF, L is open circuit Nojun Kwak

6. Impedance (driven by sinusoidal source) Nojun Kwak

7. Representation of Signal Source • The two are equivalent. • However (a) is preferred when Rs is small,  small voltage drop • While (b) is preferred when Rs is large.  small current loss Thevenin form Norton form Nojun Kwak

8. Analog Signal Analog-to-Digital Converter Discrete Sampled Signal 111 111 101 Digital Signal Analog vs. Digital Signal Nojun Kwak

9. Time and Frequency-Domain Representation of Analog Signals Amplitude (power) frequency f time t Time domain Frequency domain (frequency spectrum) t Fourier series Time & Frequency Domain Nojun Kwak

10. Frequency response (single time constant) Nojun Kwak

11. Bode plots High pass Low pass Nojun Kwak

12. Amplifiers (mostly for Analog Circuits) • Voltage amplifiers • Current amplifiers • Power amplifiers 4 ports 3 ports (common ground) The role of DC power supplies Nojun Kwak

13. Gains • Voltage Gain: Av = vo/ vi • Current Gain: Ai = io/ ii • Power Gain: Ap = Po/ Pi = vo io /vi ii = Av Ai • Gain in dB (decibel) • Voltage, Current gain = 20 log (Av, Ai) • Power gain = 10 log (Ap) • Ap (dB) = ½ [Av(dB) + Ai (dB)] * For more information, consult App. B. Nojun Kwak

14. Amp. with Power Supplies (How Po > Pi ?) Efficiency: Because PI is normally very small Nojun Kwak

15. Transfer characteristic w/ Saturation To operate linearly: Nojun Kwak

16. Nonlinearity and Biasing Small-signal gain (Av) = slope of the transfer curve at the operation point Nojun Kwak

17. Circuit models for Amps Nojun Kwak

18. Voltage amplifiers To make Vo/Vs large (regardless of source and load),  Ri  should be large Ro  should be small Nojun Kwak

19. Example: multistage voltage amps. • Cascade or multi-stage amplifier: input resistance of an amplifier stage acts as a load to the previous stage. • Typically used for Op-amp.  e.g. 741 type • Desirable characteristics for a voltage amp. • Large input resistance • Small output resistance • High gain Nojun Kwak

20. Example: BJT (small signal model) Common emitter amplifier Nojun Kwak

21. Frequency response of an amp. Nojun Kwak

22. Inverter (mostly for Digital Circuits) • Logic inverter symbol Ideal Logic Inverter Real Logic Inverter (with linear approx.) Nojun Kwak

23. Implementation of Inverters • Voltage controlled switch • Vi = low  (b) • Vi = high  (c) Nojun Kwak

24. Inverter with CMOS • CMOS – can be interpreted as a pair of complementary switches Nojun Kwak

25. Propagation delay of an inverter Nojun Kwak