I know what are logic gates and how to deal with them, and how they are so important in computer architecture. I learnt logic gates combinations and how they work.

Now I would like to know how are those gates designed?

What are the electronic components used to make a logic gate?

I just know some electricity basics!


closed as unclear what you're asking by CL., Bence Kaulics, Daniel Grillo, Voltage Spike, uint128_t Dec 6 '16 at 22:46

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ A course in spelling, capitalization and grammar might also be useful (nobody's perfect of course). \$\endgroup\$ – Andy aka Dec 6 '16 at 13:35
  • \$\begingroup\$ @Andyaka how this could help me ? my language is bad is this mockery ? \$\endgroup\$ – Mustapha Elbazi Dec 6 '16 at 13:40
  • \$\begingroup\$ Your quotation from the Quran appears to be in good order so you must ask yourself why I have made this remark. \$\endgroup\$ – Andy aka Dec 6 '16 at 13:45
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    \$\begingroup\$ Come on people. Sure the original question was fairly poor English, the edits have improved it a lot. But what he was asking was perfectly clear from the start. The point is to answer electronics questions not to complain about peoples language skills. I'm sure he did a far better job of asking the question in English than most of you could do answering it in his native language. \$\endgroup\$ – Andrew Dec 6 '16 at 14:24
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    \$\begingroup\$ @Andrew I disagree with you when you say the question was perfectly clear from the start - it certainly was not - it held contradictions that made it a bad question and, who was complaining about language skills? Do you see my observations as complaints (because they are not). I find your comment largely irrelevant (now that might be considered a complaint)! \$\endgroup\$ – Andy aka Dec 6 '16 at 14:38

The three basic building blocks are NAND, NOR and NOT gates.

You can build any logic gate you want from 2 input NAND or NOR gates. e.g. A NOT gate is a NAND gate with the two inputs connected together. An OR gate is a NAND gate with NOT gates on both inputs.

When it comes to building them just about all digital logic is these days is made of CMOS FET transistors. A NOT gate takes two transistors, a NAND gate or a NOR gate takes 4 transistors e.g. a NOR gate looks like this.


simulate this circuit – Schematic created using CircuitLab

For a NOT remove M2 and M4, for a NAND put M3 and M4 in parallel and M1 and M2 in series.

There are some optimizations you can do for more complex structures but hopefully you can see how by using these building blocks you can make any logic gates or function you want.

  • \$\begingroup\$ this make things more clear and simple . but i have no idea about those things in the schema , any reference from scratch ? \$\endgroup\$ – Mustapha Elbazi Dec 6 '16 at 14:33
  • \$\begingroup\$ Would it be fair to include nand/nor gates? If one needs to compute !((a & b) | (c & d)), one could compute it as !(!(!a | !b) & !(!c | !d)) but it would generally be more efficient to use an eight-transistor hybrid gate. \$\endgroup\$ – supercat Dec 6 '16 at 14:35
  • \$\begingroup\$ @MustaphaElbazi Have you read the WiKi page for a "Field-effect transistor"? There are tons of references at the bottom of that page. \$\endgroup\$ – Tyler Dec 6 '16 at 14:35
  • \$\begingroup\$ @MustaphaElbazi: A transistor with an arrow pointing inward to the middle will connect the source and drain (top and bottom) if the gate (the thing entering from the left) is more positive than both of them; one with the arrow pointing outward from the middle will connect the source and drain if the gate is more negative than both source and drain. \$\endgroup\$ – supercat Dec 6 '16 at 14:37
  • \$\begingroup\$ @MustaphaElbazi A FET is the smallest building block in a digital chip. While they can act as amplifiers or to give a controlled gain in these circuits they are basically acting as a switch. The bottom ones switch on when their input is high, the top ones switch on when their input is low. Google can give you far more information than you will ever need on exactly how they work. \$\endgroup\$ – Andrew Dec 6 '16 at 14:39

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