Electrical – And gate in a demultiplexer


I have a question regarding the use of an AND gate in a demultiplexer 1×4 circuit such as

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A demultiplexer truth table shows you can output a 1 signal on the zero line, if your input is 1, and both your selector line is 0.

My question is why can the demultiplexer which uses a three input(1 from data and 2 from selector line) AND gate output a 1 signal even though both the input from the selector line is 0?

Isnt the AND gate only output a 1 signal if all the input is equal to 1.

Best Answer

You are ignoring the invertors. Look more closely at the wiring.

The inputs to Y0 are Data, NOT A, and NOT B

When Data is high and A and B are low, that's three highs on the input = high on the output.

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