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This "flash analog-to-digital converter" (ADC) is the discrete-logic implementation of the homonym ADC, usually found only in discrete ICs for high performance applications (e.g. Oscilloscopes).
Run the simulaton, then change the voltage at the input, to the far left.
Since the analog comparators output a "thermometric code", their output is encoded with an encoder (here I encoded only the first 4 least significant bits using logic gates), and the output of the ADC is obtained (doubled) on the 7-segm display.
ABOUT THIS CIRCUIT
The main benefits are:
- extremely fast (the fastest type available to this day, with the current technology). The output value is ready as soon as all the comparators and gates have settled (typically 100ps ~ 1ns)
- intrinsically monotonic
The downsides are:
- extremely expensive: 1 comparator + precision resistor for each step of resolution (to be designed onto the silicon). For a mere 8 bits, you need 256 comparators and 257 resistors (all with tight tolerances).
- relatively high power consumption
- lower end implementations can lead to unbalanced voltages across the ladder: this may cause missing codes.
For these reasons, it's unlikely to be found in most common microcontrollors and DSPs, and it's instead very common in fast instrumentation (such as oscilloscopes and spectrum analyzers).
Note: this implementation *can* work without the sample-and-hold circuitry at the input stage, but for reliability reasons it's often found anyway.
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