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What is ADC full scale?
The full scale input of an ADC is the largest signal amplitude that can be delivered to the converter before the signal is clipped in its digital output representation. At full scale, the output uses the minimum and maximum codes of the ADC.
How many comparators does a 12-bit flash ADC?
bit of resolution [9]. ADC based on this technique uses only 256 comparators instead of 4096 comparators normally required in the flash ADC’s for 12-bit resolution.
How is full scale of ADC calculated?
The full scale voltage is determined from this parameter as Vrms full scale = Vrange / (2 * sqrt(2) ). The signal to noise ratio of the ADC is specified relative to the full scale rms voltage of the ADC.
Where are flash ADC used?
The very high sample rate of this type of ADC enables high-frequency applications (typically in a few GHz range) like radar detection, wideband radio receivers, electronic test equipment, and optical communication links. More often the flash ADC is embedded in a large IC containing many digital decoding functions.
Which type of ADC is fastest and why?
The flash ADC is the fastest type available. A flash ADC uses comparators, one per voltage step, and a string of resistors. A 4-bit ADC will have 16 comparators, an 8-bit ADC will have 256 comparators.
What is 10 bit ADC?
A 10-bit ADC has 210, or 1,024 possible output codes. So the resolution is 5V/1,024, or 4.88mV; a 12-bit ADC has a 1.22mV resolution for this same reference. Types of ADCs. ADCs come in various speeds, use different interfaces, and provide differing degrees of accuracy.
What does the flash ADC output look like?
The priority encoder generates a binary number based on the highest-order active input, ignoring all other active inputs. When operated, the flash ADC produces an output that looks something like this: For this particular application, a regular priority encoder with all its inherent complexity isn’t necessary.
How many comparators are needed for flash ADC?
This three-bit flash ADC requires seven comparators. A four-bit version would require 15 comparators. With each additional output bit, the number of required comparators doubles.
Which is the lowest output code for an ADC?
The output code will be its lowest (000) at less than 1/8 of the full-scale (the size of this ADC’s code width). Also, note that the ADC reaches its full-scale output code (111) at 7/8 of full scale, not at the full-scale value.
Which is the reference voltage in a 3-bit flash ADC?
The following illustration shows a 3-bit flash ADC circuit: V ref is a stable reference voltage provided by a precision voltage regulator as part of the converter circuit, not shown in the schematic. As the analog input voltage exceeds the reference voltage at each comparator, the comparator outputs will sequentially saturate to a high state.