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I have one simple question I don't understand: Why are transistors so widely used in microprocessors and complex in some manners(semiconductors, Fermi level, PN junction, etc.),while logical gates are used too but not in such huge number as transistors, while logical gates are far more simpler (for me) in use of zeros and ones (0's and 1's) inside of microprocessors?

Lucenzo97
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    What is a "logical gate?" If you're referring to "logic gates," they are created using transistors. And since it takes several transistors to make one logic gate, that explains why there are "fewer logic gates than transistors." – Robert Harvey Aug 31 '16 at 22:50
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    Aren't logic gates typically implemented using transistors? – Matthew Aug 31 '16 at 22:52
  • See also Flip-flop or latch to see how state is held by logic gates. – Erik Eidt Aug 31 '16 at 23:19
  • Aren't logic gates made of switches only? – Lucenzo97 Sep 01 '16 at 06:28
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    @LuKa: Transistors are the switches of the semiconductor world. If you want to implement a switch in the small scale of a microprocessor, you can only do that by using a transistor. – Bart van Ingen Schenau Sep 01 '16 at 07:50
  • @BartvanIngenSchenau Not to pick nits, but transistors are amplifiers, not switches. This is important to remember when, say, building a resistor out of transistors. It's easier to think of them as switches, but inaccurate. – 3Dave Sep 01 '16 at 16:54
  • @DavidLively I think there may be validity to treating transistors as both amplifiers and switches. While you are correct that transistors, at their heart, are amplifiers, within computers they are typically run in the saturated region. This region of operation is also called the switching region because of how it behaves and how it is used. We generally avoid the linear regions that are used for amplification because they generate lots of waste heat and don't do anything that the digital logic people want done. – Cort Ammon Sep 01 '16 at 17:43
  • @dwelch: NAND is easier than AND. The same transistor that inverts one input to give you a NOT can invert several inputs. See http://nand2tetris-questions-and-answers-forum.32033.n3.nabble.com/Nand-Implementation-td4026751.html for example. AND (a, b) is implemented with transistors as NOT (NAND (a, b)). – gnasher729 Sep 01 '16 at 18:46
  • @LuKa transistors have a linear region between the power rails. When using as an amplifier it essentially takes the input and multiplies it and allows that much current to flow. But you can also use it as a switch by slamming it into the rails on purpose instead of avoiding the rails. So for logic you slam it into high and slam it into low/gnd. Logic states true and false (or false and true high doesnt have to be true or one it is design specific). – old_timer Sep 01 '16 at 19:19
  • @dwelch So if I understood you correctly we can conclude the whole thing about transistors and gates like this: When transistors are used for amplification, they are used in its linear region for higher or more efficient gain (not in saturation region). But when transistors are used in terms of switching or logic gates they are used in its saturation region, because the point of switching is not amplification but applying voltage to specific part of a circuit. If this definition is not correct, please correct it. – Lucenzo97 Sep 03 '16 at 13:04

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Expanding on Robert Harvey and Matthew's comments, logic gates are a mathematical abstraction. Physical devices that emulate the abstract notion of a logic gate have been built from a variety of components: gears and cams, electromechanical relays, diodes, vacuum tubes, transistors, and LEGOs. Transistors etched into silicon chips currently offer the best combination of price, reliability, speed, and density (by several orders of magnitude).

Community
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Charles E. Grant
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Why are transistors so widely used in microprocessors...while logical gates are used too but not in such huge number as transistors

As explained in the comments, transistors are the building blocks from which logic gates are constructed. Transistors aren't used instead of logic gates, they're used to make logic gates. Here's an AND gate built from transistors, which are represented by the symbols in the circles:

AND gate (Image credit: EBattleP)

To be fair, some gates like AND and OR can be created with diodes instead of transistors. Conversely, transistors are used for more purposes than just building logic gates. With respect to your question, though, the thing to remember is that transistors aren't used in place of logic gates, but rather when logic gates are needed, they're typically implemented using transistors.

while logical gates are far more simpler (for me) in use of zeros and ones (0's and 1's) inside of microprocessors?

If you're thinking in terms of logic gates, you don't need to worry about how they're implemented -- you just trust that they work. The particulars of how the gates are constructed don't affect your reasoning at the gate level. For example, here's a demo of AND and OR gates built from pneumatic components, and if you were so inspired you could build a pneumatic version of anything you can make from those gates.

Caleb
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  • For stability most gates/logic arrays are often built out of more than just the minimum possible number of transistors/diodes. – Matthew Whited Sep 01 '16 at 17:29
  • I apologize for my ignorance about logic gates. An yes, this really helped me to understand logic gates in terms of architectue. Thanks! – Lucenzo97 Sep 03 '16 at 12:48