1. 1.2 Analog Versus Digital Next t v(t)v(t) 0 Analog signals: time-varying signals that can take on any value across a continuous range of voltage, current, or other metric. Return 米制的, 公制的

2. 1.2 Analog Versus Digital NextBack Digital signals: at anytime,only one of two discrete values, which we call 0 and 1. ( or Low and High, False and True, negated and asserted, or whatever) t v(t)v(t) 0 0 1 0 1 1 0 0 1 TsTs Digital systems must be circuits to process binary digits – 0s and 1s according to the definition of digital signals. Are there any benefits? Return 否定 肯定

3. 1.2 Analog Versus Digital How to convert analog signals to digital signals? (A/D Converter) Analog signal A/D 0.2V Ref. Voltage +5V t v s (t) Sampling v q (t) t Quantization v (t) t 0.2 Signal 0 0 0 0 1 0 1 0 Coding NextBack Return

4. Examples of Digital Systems:  Still pictures. JPEG, BMP, GIF 1.2 Analog Versus Digital  Video recordings. DVD (Digital Versatile Disk), VCD (Video Compact Disk), MPEG, AVI  Audio recordings. CD (Compact Disc), WAV  Automobile carburetors. Microprocessor is embedded. It can determine how to control the flow of fuel and oxygen to the engine.  The telephone system. Digital COs & PBXs.  Traffic lights. Controllers use microprocessors. NextBack Return 汽化器

5. 1.2 Analog Versus Digital The Reasons that Digital Circuits Over Analog Ones  Reproducibility of results  Ease of design  Flexibility and functionality  Programmability  Speed  Economy  Steadily advancing technology Back Return