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8.
An Analog Electronic System
Original sound waves
Amplified audio signal
Microphone
Linear
Audio signal
amplifier
Speaker
9.
A System Using Digital and Analog Methods
Although you will be studying digital fundamentals in this book, you should also know about analog because many applications require both.
7.
The Digital Advantage:
EXAMPLE 1-1 Determine the following (a) period
tw
(b) frequency (c) duty cycle
T
0 1
10 11
t(ms)
Solution:
(a) T = 10 ms (b) (c) f = 1/T =1/10 ms =100 Hz Duty cycle = (tw/T)*100% = (1/10)*100%=10%
§1.1 DIGITAL AND ANALOG QUANTITIES
Today, digital technology is applied in a wide range of areas. Such applications as television, communications systems, radar, navigation and guidance systems, military systems, medical instrumentation, industrial process control, and consumer electronics use digital techniques.
13.
Logic Levels ( TTL )
V VH(max) 5V
HIGH ( 1)
VH(min) 2V
Unallowed
VL(max) 0.8 V
LOW ( 0 )
VL(min) 0V
14.
Digital Waveforms
Digital waveforms consist of voltage
DIGITAL
Digital [ 数字的 ] Bit [ 位 ] Clock [ 时钟 ] Data [ 数据 ] Parallel [ 并行 ]
Discrete [ 离散的 ] Clarity [ 清楚 ] Amplifier [ 放大器 ] Reproduction [ 复制品 ] Compact disk [ 光盘 ] Laser [ 激光 ] Diode [ 二极管 ] Optical [ 光学的 ] Code [ 编码 ] TTL [ 晶体管-晶体管逻辑 ] Edge [ 边沿 ] Amplitude [ 幅值 [ 转换 ] Reciprocal [ 倒数 ] Instantaneously [ 同时 ] Stray capacitive [ 杂散电容 ] Duty cycle [ 占空比 ]
levels that are changing back and forth between the HIGH and LOW levels or states.
15.
HIGH Falling or Rising or leading edge LOW t0 t1
trailing edge
(a) Positive-going pulse
Clock : The basic timing signal in a
digital system; a periodic waveform in which each interval between pulses equals the time for one bit. Timing diagram : A graph of digital waveforms showing the time relationship of two or more waveforms.
Gate : A logic circuit that performs a
specified logic operation such as AND or OR. Data : refers to group of bits that convey some type of information. Serial : Having one element following another, as in a serial transfer of bits; occurring in sequence rather than simultaneously.
6.
Electronic circuit can be divided into two broad categories, digital and analog. Digital electronics involves quantities with discrete values. And analog electronics involves quantities with continuous values.
For one thing, digital data can be
processed and transmitted more
efficiently and reliably than analog data. Also, digital has a great
advantage when storage is necessary.
CD drive
Analog
reproduction of music audio signal Digitalto-analog Digital data converter
Linear
amplifier
( DAC ) 10.
§1.2 BINARY DIGITAL, LOGIC LEVEL, AND DIGITAL WAVEFORMS
KEY AND KEY TERMS
Analog : Being continuous or having
continuous values. Digital : Related to digital or discrete quantities; having a set of discrete values. Binary : Having two values or states; describes a number system that has a base of two and utilize 1 and 0 as its digits.
11.
The two states can also be represented by current levels, open and closed switches, or lamps turned on and off. In digital systems, combinations of the two states, called codes, are used to represent numbers, symbols, alphabetic characters, and other types of information.
3
That is one small step for a man,
one giant lead step for mankind.
4
1 ： INTRODUCTION CONCEPTS
Analog [ 模拟 ] Binary [ 二进制 ] Pulse [ 脉冲 ] Timing diagram [ 时序图 ] Serial [ 串行 ] Logic [ 逻辑 ]
17.
The duty cycle is defined as the ratio of the pulse width ( tw ) to the period ( T ).
( frequency ) f = 1/T
( period ) T= 1/ f tw T
18.
Duty cycle =
100 %
Bit : A binary digit, which can either a 1
or a 0. Pulse : A sudden change from one level to another, followed after a time, called the pulse width, by sudden change back to the original level.
CHAPTER 1
INTRODUCTORY DIGITAL CONCEPTS
“ Moon Walk, In July of 1969 . 240,000 miles ” 0100010 1010100 1101000 1100001
1110100 0100111 1110011 0100000
1101111 1101110 1100101 0100000 1110011 1101101 1100001 1101100 1101100 0100000 1110011 1110100 1100101 1110000 ………
Parallel : In digital systems, data occurring
simultaneously on several lines; the transfer or processing of several bits simultaneously. Logic : In digital electronics, the decisionmaking capability of gate circuits, in which a HIGH represents a true statement and a LOW represents a false one.
