Flash Analog to Digital Converter

Flash analog-to-digital converters, also known as parallel ADCs, are the fastest way to convert an analog signal to a digital signal. Flash ADCs are ideal for applications requiring very large bandwidth, but they consume more power and much bigger in size than other ADC architectures. A Flash converter requires a huge number of comparators compared to other ADCs, especially as the resolution increases. A Flash converter requires 2n-1 comparators for an n-bit conversion.

Notes:

  • Circuit shown is a 3 bit flash converter
  • Reference ladder consists of 2n (23 = 8) equal size resistors
  • Input voltage is compared to 2n-1 reference voltages using 2n-1 comparators. The reference voltages can be calculated using KVL.
  • A Priority Encoder is used to transform the comparator outputs to the correct digital binary output.
  • Change the input voltage and observe the comparators and the priority encoder digital outputs.