【模拟电子】从放大器说起（序章）（ZT） by 89723221@qq.com
时至今日，越来越多的东西被冠上“数字（digital）”的前缀：数字随身听（mp3），数码相机，数码相框……一直到数字化生活，那么在浩如烟海的数字设备出现之前我们采用的是什么技术呢？
首先来看看什么叫做“数码产品”，数码产品得名于内部使用数字电路进行信息的储存和处理。所谓“数字”是指仅仅采用有限个离散的状态来储存和表示信息，例如数字电路中常见的利用“0”和“1”来表示和储存数据，由于这两个状态的差别往往非常明显，因此在储存，传输和处理的过程当中不易损坏和失真。
相对的，如果采用连续的状态来表示，储存和处理信息的方式就被称为“模拟（analog）”。由于表示的是无数连续状态中的一个，那么任何一点点的干扰都会使模拟的信号发生失真 。用一个形象的比喻说数字和模拟技术的区别就是，数字技术像写书，每次抄写和复印都不会使书得内容发生变化；而模拟技术像绘画，就算是临摹的再好和原作也是有区别的，所以复制N次之后往往会大有不同。
然而自然届中绝大多是的信号和事件都是以模拟的形式存在的，比如人眼的7色彩虹是连续变化的，用再高倍数的望远镜也没法出其中的”像素“。而人类在开始使用绘画，摄影，留声机等技术来记录这些信息的时候也都是从模拟的方式开始的。
从很早开始人们就不再仅仅是被动地接收自然界得模拟信号，而开始主动的对这些信号进行处理了，其中放大器是运用得最为广泛，也是最早的方式之一。我们每天都会开关水龙头，这个动作就可以看做是一个典型的模拟信号放大系统——我们用很小的力控制水龙头的位置却可以得到流量可变的，压力很大的水流。
When people entered the electrical age, they began to explore the amplification of electrical signals. In 1880, Edison added a third electrode in addition to the two electrodes of the ordinary bulb in the experiment of bulb research, and added some foils. He was surprised to find that the foil was positive when the third pole was positive. No reaction, but the foil has a churning motion when the battery is negative. His inadvertent discovery is actually the prototype of a vacuum electronic diode.
In 1904, John Fleming invented the vacuum diode based on the principle of the Edison effect, and in 1907 Lee DeFrest invented the first vacuum transistor, and the world entered the electronic age. After that, in 1947, semiconductor technology-based bipolar transistors were invented by Bell Labs's John Bardington, Walter Braden, and William Shockley. Electronic technology entered a golden age of leaps and bounds. The more you enter into people's lives.
The essence of an analog amplifier is to use a signal of smaller amplitude or power to control a signal of greater amplitude or power. For example, electric guitars, everyone knows that many electric guitars do not have a resonance chamber. The actual sound produced by hand plucking strings is actually very small, but the electronic amplification device used can generate the sound that the entire stadium is boiling. A magnet is placed under the strings of the electric guitar. When the metal strings vibrate, the magnetic induction lines of the magnets are cut to generate a weak voltage, and these voltages are used as inputs of the amplifier to control the electric signals of the higher power to drive the speakers. Produces a loud sound. The power amplifiers that originally used tubes have at least a suitcase size, and the semiconductor technology power amplifiers currently used in cell phones are only a few square millimeters.
Although more and more signal processing in life, storage uses digital technology, but the simulation technology is still used in our observation of the world's entrance hospital biochemical equipment, optical sensors in the camera, accelerometers and gyroscopes in mobile phones, etc. They are all state of the art analog technology.
In the era of digital survival, we still cannot do without traditional analog technology, because the real world is always "simulated."