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1 .J. Chen Chapter 1 Introduction to Electronics 1.1 Signals 1.2 Frequency Spectrum of Signals 1.3 Analog and Digital Signals 1.4 Amplifiers 1.5 Circuit Models for Amplifiers 1.6 Frequency Response of Amplifiers 1.7 Digital Logic Inverters 1.8 Circuit Simulation Using SPICE
2 .J. Chen 1.1 Signals Parameters in the real world Transducer 传感器 / 换能器 Electrical signal (a) Thévenin form (b) Norton form Signal sources
3 .Sine-wave: temporally and spatially determined by Amplitude, Frequency/Period and Phase J. Chen 1.2 Time & Fr equency -domain expression and spectrum Sine-wave voltage signal and its spectrum ( rad/s ) 0
4 .J. Chen Time-varying signal in arbitrary form→ FT →sum of sine-waves. e.g. symmetrical square-wave 1.2 Time & Fr equency -domain expression and spectrum
5 .J. Chen Sine-wave is always used for analysis, design and testing. Frequency spectrum of the periodic square wave 1.2 Time & Fr equency -domain expression and spectrum
6 .J. Chen Spectra of some typical signals Spectrum of CWDM signal Spectrum of laser signal Spectrum of Human Voice 0 500 1000 1500 2000 2500 3000 (Hz) A 1.2 Time & Fr equency -domain expression and spectrum
7 .J. Chen 1.3 Signals: analog v.s . digital Delay evolution over 24 hours in a optical fiber system for Time/Frequency transfer Code format of the standard IRIG-B(DC) AD DA
8 .J. Chen 1.4 Amplifiers Electronic circuits can perform many analog and digital signal processing functions This course mainly deals with the simplest but most important function —— Amplification (b) With a common terminal (ground) (a) Circuit symbol Direction of signal flow
9 .1.4 Amplifiers Both voltage and current can be amplified. Hence there are different types, depending on the practical application scenery. Source, Input and output resistances The gain (V/V, A/A, V/A, A/V ) For a particular amplifier, some gains may be less than one. However, the signal power is certainly amplified. J. Chen
10 .1.4 Amplifier: types and key parameters Amplifier types Signal intension (small signal amp., power amp., …) Signal spectrum (wideband amp., tuned amp.,...) … Key parameters Gain, inpu t/output resistance, … Bandwidth Linear & Nonlinear distortion, Saturation ….. J. Chen
11 .1.4 Power s upplies and Biasing DC sources are required, not only to bias the circuit for appropriate operation, but also to provide power J. Chen (a) An amplifier with two dc supplies (b) Usual form(Simplified)
12 .1.4 Units & Decibel J. Chen Decibel (dB): a dimensionless number in logarithmic scale.
13 .J. Chen e.g. The lowest audible intensity is about I 0 =10 -12 （ W/m 2 ）； In general, the sound intensity is expressed in dB in relative to I 0 as: The maximum sound intensity human beings can bear is about 1 （ W/m 2 ） , or 120dB 。 1.4 Units & Decibel
14 .DC: Uppercase, AC: Lowercase Total instantaneous quantity, Incremental signal quantity, DC component, Power supply, , Amplitude of a sine wave, 1.4 Symbol convention J. Chen e.g.
15 .J. Chen 1.5 Circuit models for amplifiers Mathematical description of the device physical characteristics, useful in quantitative analysis. ( b ) The voltage amplifier with input signal source and load (a ) Circuit model for the voltage amplifier
16 .J. Chen 1.5 Circuit models for amplifiers Different device has its own model. A device may have few different models according to the purpose, precision, applications, etc.. (b) An alternative small-signal circuit model for the BJT (a ) Small-signal circuit model for a bipolar junction transistor (BJT) (c) BJT model for high frequency analysis
17 .1.6 Frequency response of amplifiers The band of frequencies, over which the gain is almost constant (within 3 dB ) is called the amplifier bandwidth . J. Chen Typical magnitude response of an amplifier 3dB
18 .1.6 Frequency response of amplifiers Frequency response of amplifiers can be evaluated using Basic Circuit Theory Single-Time-Constant (STC) Networks J. Chen Two examples of STC networks (a) a low-pass network (b) a high-pass network
19 .1.6 Frequency response of amplifiers Single-Time-Constant (STC) Networks J. Chen ( b) P hase response (a) Magnitude high-pass low-pass
20 .1.6 Frequency response of amplifiers Classification of amplifiers based on frequency response. J. Chen (a) Capacitively coupled amplifier (b) Direct-coupled amplifier (c) Tuned or bandpass amplifier
21 .1.7 Digital logic inverters Out of scope Those, who are going to be engaged in the R&D of electronic circuit related areas, are advised to read the content. Especially, attention should be paid to Power Dissipation and Propagation Delay . J. Chen
22 .J. Chen Chapter 2 Operational Amplifiers
23 .J. Chen Operational Amplifiers The Gain open-loop gain. closed-loop gain differential gain The terminals inverting input terminal( 反相输入端 ) noninverting input terminal( 同相输入端 ) The Common mode rejection ( 共模抑制比 )
24 .End of Chapter 1 & 2 J. Chen
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