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Im trying to create the 74XX series IC's from scratch, using just transistors, resistors and diodes. I intend to chain them together and create some logic systems. Right now i'm trying to create a basic NAND gate but i can't find any transistors with at least two emitters. Why? Can i just take two transistors and solder together first the bases and then the collectors? Or maybe create it from diodes?

What i want to know is where can i obtain such a transistor or how to make one. I know how it works and where its used.

Here is an image of a NAND TTL gate: TTL NAND gate

Moomba
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  • Your schematic is missing a great deal; see http://www.physics.mcmaster.ca/phy4d6/Lab/chapter6.htm – Peter Smith Jan 15 '17 at 15:25
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    The closest thing you can do is use two transistors with shared collector and shared base; but that will be, behavioural, still pretty different from this circuit. It's something you can deliberatly design when doing a silicon wafer, but not well at all when doing this in discrete. In other words, **when implementing the same logic function in discrete technology, you can't use the same schematics as for IC implementation**. That's a technological limit. – Marcus Müller Jan 15 '17 at 15:28
  • So are you saying this is impossible to create using discrete technology? What are the alternatives besides IC's? I really want to avoid having to buy some. – Moomba Jan 15 '17 at 15:32
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    Come up with your own discrete-transistor based logic. It will probably be much slower, use much more power and be very complicated, but it's possible. This, however, feels like half the truth: **why** don't you want to buy simple logic ICs? What is your application, what is your reasoning? – Marcus Müller Jan 15 '17 at 15:36
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    I find it fascinating to create old-school circuits, before the era of IC's. I just want to see every little transistor, resistor, everything that makes up the circuit, instead of having it hidden under a black abstract box. Don't get me wrong, i love IC's and made several projects involving PIC microcontrollers and gates. But i want to go even more low level. Right now i want to create an 8-bit adder. – Moomba Jan 15 '17 at 15:41
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    Try this http://eff10.internetdsl.tpnet.pl/komputer/elektro/rys/r809_817a.gif or this why http://www.krzysiekirzyk.republika.pl/arch/htm/grafika/ki30.gif – G36 Jan 15 '17 at 15:45
  • @G36 the first link contains transistor symbols with Zener-like vertical bars; any info on what that means? – Marcus Müller Jan 15 '17 at 16:56
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    @Moomba thanks for the clarification! Yeah, if you want to go pre-IC era, you really can't use the equivalent schematics of ICs (they are imperfect, "function principal" equivalent models, only, anyway), and might want to look into [Diode-transistor logic](https://en.wikipedia.org/wiki/Diode%E2%80%93transistor_logic) devices! – Marcus Müller Jan 15 '17 at 17:02
  • @MarcusMüller the transistor symbols with Zener-like vertical bars are Schottky transistors: https://en.wikipedia.org/wiki/Schottky_transistor – John D Jan 15 '17 at 18:44
  • @JohnD aaaah! A clamped transistor! Great, thanks :) – Marcus Müller Jan 15 '17 at 18:45
  • @Moomba An 8-bit adder from BJTs?? Do you want to use RTL, DTL, TTL, or ECL technology to achieve that? Are you aware that you will need almost 100 BJTs to get there, using RTL? (You could also consider building a FAB of sorts. I've done it in a garage and Bell Labs used to sell a kit you could use to make an oven and a solar cell. Plus, see this relay computer: http://web.cecs.pdx.edu/~harry/Relay/ ) – jonk Jan 15 '17 at 20:04

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