An Analog to Digital Converter (ADC) is one of the most useful electronic integrated circuits ever invented. As the microprocessors in our computer can only handle digital data, ADC perform the very important task of converting continuous, analog data into its discrete and digital equivalent.
ADCs play a crucial role in bridging the gap between analog equipment like transducer and the world of digital signal processing. By converting data into its digital equivalent, ADCs reduce the chances of signal deterioration due to noise while also enabling us to store, modify and transmit this digital data.
Often the aspect of analog to digital converters that people fail to understand is the Effective Number of Bits (ENOB). People have started using ADCs with a lower number of effective bits which can significantly limit the applications they can use the IC for.
Also, some people just focus on the number of bits while neglecting other important parameters, which can have disastrous consequences for their electrical circuits. To improve people’s understanding of the subject matter, we’ve compiled a list of factors they need to consider when selecting an ADC.
1. Sampling Rate:
Before we even begin talking about the effective number of bits, it’s important to look at another, more important deciding factor, i.e. the sampling rate.
Measured in Hertz (or cycles per second), the sampling rate gives information about how frequently the ADC will collect samples from the analog signal. Higher the number of samples taken (sampling rate), higher will be the quality and the accuracy of the digital conversion.
Generally speaking, the sampling rate is often determined by the Nyquist Sampling Theorem. The theorem states that in order to avoid aliasing (loss of information), the frequency at which an analog signal is sampled needs to be greater than twice the highest frequency component in the signal. Mathematically,
fs ≥ 2fm
2. Effective Number of Bits:
Once you have determined the sampling rate of your ADC only then should you take a closer look at its effective number of bits. Simply put, the number of bits gives us information about how accurately the ADC can convert analog data into its digital form.
In its essence, the effective number of bits gives us information about the number of levels the ADC will use to translate analog data to its digital form. The relationship between the number of levels and the number of bits is given by the formula;
Number of levels (N) = 2n
Where, n = number of effective bits
So, if you were to use a 4-bit ADC, you would get 24 = 16 levels. This can lead to high quantization error and will massively limit the accuracy of your ADC and make it unsuitable for high speed applications. This is why we believe people should opt for an 8-bit ADC instead (which has 256 levels).
3. Resolution:
Finally, the last metric you should analyze when buying an ADC is its resolution. Simply put, the resolution of the ADC gives information about the voltage of each level of the ADC. The resolution of an ADC is given by the following mathematical relation,
So, for a common 4-bit ADC powered by a 0 to 5 volts power supply, the resolution will be:
Resolution = 0.3125 Volts per level
This means if the analog signal varies quickly, your ADC will be prone to quantization error and noise. On the other hand, an 8-bit ADC (powered by the same DC source) will have a resolution of 19.5 mVolts per level (5/256 = 0.019531), which makes it a much better option for circuit designers to consider.
That being said, a higher bit ADC will require more (memory and other resources) from your computer which can make them slower as far as processing data is concerned. Therefore, make sure that your computer can handle the increased expectations before investing in an 8-bit ADC.
Where to Buy ADCs:
The ADC is an integral part of any electrical design which is why you should be very careful where you buy them from. ADSANTEC has become renowned for providing quality integrated circuits and electrical solutions. We have a huge library of electrical components like analog to digital converters, serializers, variable delay lines and signal generators.
Contact us today to make circuit design and realization more efficient!