# Universal gates

1. Nov 7, 2012

### Avichal

I had no idea where to post questions related to Boolean algebra and logic gates, so I thought that the logic section would be good enough. If not please move it.

Anyways are there any parameters that a gate must satisfy to be a universal gate. NAND and NOR gates are universal gates while others are not. Whats so special in these gates that make them universal. So are there any parameters such that we look at them and can judge if a gate is universal or not?

2. Nov 8, 2012

### vk6kro

NOR and NAND gates can be used to make most other types of gate, if you use enough of them.

Other gates such as the AND gate cannot, because they cannot do an inversion, no matter how you connect them.

So any desired gates that involve an inversion function can't be made with AND gates (or OR gates either). So, they are not universal gates.

3. Nov 8, 2012

### Avichal

What about XOR gates. They can do inversion but they are not universal. So inversion is not a parameter to decide if a gate is universal

4. Nov 8, 2012

### vk6kro

Well, they must at least be able to do an inversion.

Maybe then potential universal gates have to be evaluated on their individual properties, unless you already know an answer to your own question.

5. Nov 8, 2012

6. Nov 8, 2012