Does the speed of an ADC depend on the number of bits used. So is 8 bit faster then 16 bit?
The relationship between the conversion speed and the resolution ( number of bit ) of Analog to Digital converters is complex. It depends on the types of ADCs you are looking at. A successive approximation converter ( SAR ) generally takes one clock cycle per bit of resolution so the conversion time ( speed ) to the first order depends directly on the resolution. On the other hand take a Flash ADC, where a conversion takes just one clock cycle independent on the number of bits. In this case since there is one analog comparator per quantization level all possible outputs are tested at the same time ( in parallel ) with one clock cycle. There are many other ways that an ADC can be constructed that fall between these extremes and many other factors besides the number of clock cycles, such as settling time to within a certain error band
( LSB size ).
So in answer to your question, maybe, sometimes, it depends....
If you could be more specific about the kind of ADC you are interested in and the application you would be using it for then we might be able to provide a more detailed answer.
Thanks for your reply. So the relation for conversion speed and number of bits depends on the type of adc used.I plan to use adc for ccd image sensor. What kind of adc will be suitable for ccd image sensor. I am looking for adc 12 bit and 5MSPS.
There are many more specifications than just resolution and sample rate that go into selecting the optimal ADC for a given application. So rather than going back and forth one spec at a time in this Forum, I would recommend you try our parametric search to find the best part. From the Analog Devices home web page click through the parametric search tab to analog to digital converters. We use 10 MSPS as the dividing line between high and low speed converters. Since you are looking at 5 MSPS which is very near the line I would suggest you look at parts both below and above 10 MSPS. There may be more choices above 10 MSPS. Also there are more choices with greater than 12 bits below 10 MSPS so you might consider parts with more than 12 bits.
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