Flash converters are A/D converters where all logical decisions are executed in parallel. They correspond to the parallel converters and are characterized by an extremely fast conversion speed, which is only one clock cycle short.
In flash converters, the analog input signal to be digitized is fed in parallel to many comparators, where it is compared with reference voltages generated by multi-stage voltage dividers. A separate comparator is required for each possible output value, which means that the number of comparators depends on the resolution and corresponds to "2expn -1". This means that a flash converter with a resolution of 4 bits consists of 15 (16-1), one with 8 bits resolution consists of 255 (256-1) comparators.
The comparators have two inputs. One input is connected to the input voltage, the other receives its own reference voltage via a resistor matrix. The voltage division for the reference voltage depends on the resolution of the flash converter and results from the full scale value and the number of comparators. Since the accuracy of the voltage divider directly affects the accuracy of the D/A conversion, the resolution of flash converters is rarely higher than 10 bits. On the other hand, the conversion speed is very high, because only one clock pulse is needed for the full resolution.
For each clock signal, the analog input voltage is converted into a digital signal with the corresponding resolution (depending on the number of comparators). The reference voltage applied to each comparator varies in magnitude and is compared to a discrete transfer value. This transmission value is graded into least significant bits( LSB), which are obtained by dividing the modulation range (full scale) by 2expn. The outputs of the comparators simultaneously represent "2expn -1" discrete digital states whose levels are encoded and digitized.
Flash converters are used for the acquisition of short-time processes due to their high conversion speed. For example in digital oscilloscopes.