Define Flash Analog to Digital Converters?

Parallel flash ADCs transform the analog input voltage faster as compared to other types of ADCs.  They compare the voltage in parallel along with a series of comparators which are attached to a resistive network. 

Their main benefit is that they work very fast as they produce a digital output in a single cycle.  They are the just one type of converters that can be used for very high-speed conversions like video processing.  Their drawback is that the resistors in the network should be matched and laser-trimmed for accuracy.  Due to the exponential increase in components, flash ADCs are extremely expensive if more than 6 bits are required.