Very few physical systems or phenomena are digital, which means we need to convert analog information to digital and back again when interacting with the outside world.
Example: Phone converts digital representation of caller’s voice to an analog signal that can be processed by your ear.
- First, the processing system takes the digital information and converts it to an analog voltage signal with an Digital to Analog Converter (DAC)
- Analog voltage signal drives the speaker to create an analog sound wave
- If you want to reply, microphone is used to convert the sound waves of your voice to an analog voltage signal, which is converted to digital values by an Analog to Digital Converter (ADC).
There are physical limitations of ADCs, which combined with the frequency of practical analog voltage signals, means an additional piece of hardware is needed. This hardware is called the sample and hold block and is used to make a clean conversion possible.