Analog to Digital Converters - ADCs

An Analog-to-Digital Converter (ADC) is a device that converts a time-varying analog signal to a digital number representation of the amplitude of that signal. Almost all real world physical signals are analog in nature. Some examples include sound, light, temperature and motion. A transducer is a device that may be used to convert a physical signal of interest into an analog electrical signal that ultimately drives the input of an ADC. There are many key performance parameters of an ADC. The two main ones are sample rate and resolution. The ADC sample rate is the frequency at which the input signal is sampled. This sample rate dictates the maximum bandwidth of the input signal and typically is higher than twice the highest input signal, also known as the Nyquist rate. The resolution of the ADC determines how accurately the discrete digital representation it can produce over the range of analog values. Many different kinds of ADCs are available. Flash ADCs (not to be confused with Flash memory) are used for high-speed analog-to-digital conversion but are relatively power hungry. Successive approximation ADCs sacrifice speed and accuracy to obtain a low-cost, low-power conversion. Delta-sigma based ADCs use oversampling, and quantization noise shaping to achieve a very high resolution at the cost of speed. Pipeline ADCs are used in high speed applications with higher resolution needs at the expense of higher power and latency.