Analogue to digital converters are an indispensable part of consumer electronics today. They are used to convert analogue signals, such as light picked up by a digital camera, into digital signals. There are four factors that require consideration when selecting an ADC: Speed, Accuracy, Resolution and Noise.
Need for speed
Speed determines the number of conversions the ADC can do in a second. The output is called a sample, and therefore, the speed of an ADC is specified as samples per second. Flash type ADCs have one of the shortest conversion times. The fastest ADC in the industry runs at 10.4 GSPS; however, an ADC of 8 GSPS or above is considered fast enough for regular use.
Accuracy to amaze
Accuracy in an ADC refers to how closely the output matches the input. Accuracy is measured through a signal to noise ratio (SNR), where the higher the SNR, the better. Even in the most accurate ADC, some amount of noise is inevitable. ADCs with a higher resolution typically provide higher accuracy as well.
Racing for resolution
Resolution refers to how many output bits the ADC can generate per conversion. It is the number of bits required by an ADC to digitise the input sample or samples. Resolution can also be expressed in volts. In most cases, the resolution of an ADC is limited if the SNR is low. ADCs with 12 bit resolution rates are common, but any ADC with a 16-24 bit rate will offer high resolution.
Look out for noise
When a continuous set is converted to a discrete set, loss of some information is inevitable. This lost information is referred to as quantising noise. Quantisation noise is one of several types that contributes to the accuracy of the ADC. Some noise is unavoidable when converting with an ADC.