Analog-to-digital converter

Analog to digital converter is electronic circuit which  make analog signal digital. in other words we can say that ADC is basic and very important circuit in modern era of life. when we speak ,microphone  produce analog signal. this signal is then amplified and then before transmission, it is converted to digital form.

Analog signal is continuous signal as like sine wave, sawtooth wave etc while digital signal is discrete signal in the form of 1 and 0. Any of the input or analog signal is converted to digital if transmitted. There are a lot of methods to convert the analog signal into digital form. Mostly used methods are comparators. In comparator one reference voltage is given while on other terminal signal is provided. This comparator gives output if signal voltage is greater or equal to the reference as 1 and 0 vice versa. Here also keep in mind that resolution of digital signal is also important. It mean the signal you are converting into digital form, how many bits signal do you want. one bit, 2 bit,4bit,8bit,16bit  32 bit 64 bit etc. Now a days laptop and window are operation on 64 bit processors.

Amplitude modulation

Modulation is method to impose signal on carrier frequency. There are many methods to do this. Amplitude modulation is one of those methods. In this method signal and carrier frequency are mixed in such a way that amplitude of carrier frequency changes according to signal. This is very old method. In this method there is a lot of noise. in simple it is also called AM modulation. Its range according to other methods is long for transmission but there is lot of noise which is added automatically. It circuit and working is very simple. it is shown in figure.

Keep in mind when amplitude modulation is done there are two signal bands. One upper side band and other lower side band. One of these bands are transmitted some time both of the bands are transmitted and in receiver one band is suppressed and  other is demodulated to get signal. In old system of radio there was AM modulation used. Now it is also used but very rarely.