Flash ADC trade-off What is the primary disadvantage of a flash (parallel) analog-to-digital converter architecture?

Introduction / Context:
Flash ADCs are the fastest ADC topology, used in high-speed data acquisition and RF front ends. However, their speed comes with a key cost.

Given Data / Assumptions:

• N-bit flash ADC uses 2^N − 1 comparators.
• Resistor ladder and thermometer-to-binary encoder are part of the design.

Concept / Approach:
The parallel comparison of the input against all thresholds simultaneously yields near-instant conversion, but the hardware scales exponentially with resolution, making higher-bit flash ADCs area- and power-intensive.

Step-by-Step Solution:
State comparator count: for N bits, need 2^N − 1 comparators.Implication: doubling resolution by 1 bit nearly doubles the comparator count.Conclusion: the large comparator requirement is the primary disadvantage.

Verification / Alternative check:
Example: 8-bit flash → 255 comparators; 10-bit → 1023 comparators.

Why Other Options Are Wrong:
Long conversion time: false; flash is the fastest.Input applied simultaneously and output lines: not the core limiting disadvantage compared to comparator count.

Common Pitfalls:
Confusing flash with successive-approximation or integrating ADCs, which trade speed for hardware complexity.

Final Answer:
a large number of comparators is required to represent a reasonable sized binary number