Editing Analog-to-digital converter (section)

===Direct-conversion===
{{main|Flash ADC}}
A direct-conversion or flash ADC has a bank of [[comparator]]s sampling the input signal in parallel, each firing for a specific voltage range. The comparator bank feeds a [[digital encoder]] [[logic circuit]] that generates a binary number on the output lines for each voltage range.

ADCs of this type have a large [[Die (integrated circuit)|die]] size and high power dissipation. They are often used for [[video]], [[wideband communications]], or other fast signals in [[optical storage|optical]] and [[magnetic storage]].

The circuit consists of a resistive divider network, a set of op-amp comparators and a priority encoder. A small amount of hysteresis is built into the comparator to resolve any problems at voltage boundaries. At each node of the resistive divider, a comparison voltage is available. The purpose of the circuit is to compare the analog input voltage with each of the node voltages.

The circuit has the advantage of high speed as the conversion takes place simultaneously rather than sequentially. Typical conversion time is 100&nbsp;ns or less. Conversion time is limited only by the speed of the comparator and of the priority encoder. This type of ADC has the disadvantage that the number of comparators required almost doubles for each added bit. Also, the larger the value of n, the more complex is the priority encoder.