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Flash Analog to Digital Conversion

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There are 3 comparators, the outputs of which need to be encoded into 2 bits. The most significant bit (MSB) gets set to 1 as long as the signal is at least 2.5 V, while the least significant bit (LSB) gets set if either the 3.75 V comparator output is positive or the 1.25 V comparator is ON and the 2.5 V comparator is OFF. Adding logic gates (the pointed output gate is OR, the rounded end is AND, and a small circle indicates logical NOT), the full circuit is:

flash with logic

To get an encoding of 4 output levels, we required 3 comparators. How many comparators would we need for 256 output levels (8 bits)?

 

   
 

 

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