I was trying to recreate the following ADC (using comparators or NAND/NOR logic elements) circuit to control a 74HC4514 with a 0-5V voltage, but for some reason it doesn't behave as it should.
Looks like the outputs of the ADC aren't either ON or OFF, but transition between those states and messing up the stages on the 74HC4514. I tried to do the ADC circuit with a 74HCT00, 74HCT02 and 74HCT04, but all with the same result. When using Op-amps as comparators, all outputs are either ON or OFF.
There must be something I'm missing in this simple circuit, any ideas?