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Discreet Four Bit Adder

This is a discreet four bit adder I designed and constructed using 60 RTL NAND gates.

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This is a discreet four bit adder I designed and constructed using 60 RTL NAND gates.

This is a discreet four bit adder I designed and constructed using 60 RTL NAND gates.

All the gates are designed using RTL (transistor resistor logic). In order to keep the transistor count down, the adders use positive and floating signals rather than the traditional positive and negative signals used in digital electronics. This allows the board to use 2/5ths of the digital transistor count.

nandcircuits.circ

All of my prototyping and planning for the research. The final design is under NAND adder. It is in a .circ file, read by logisim.

circ - 76.93 kB - 12/16/2018 at 20:24

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  • 60 × NPN Transistor
  • 60 × 10k Ohm Resistor
  • 30 × 470 Ohm Resistor
  • 10 × Small Prototyping PCBs
  • 2 × Large Prototyping PCBs

  • 1
    Constructing the NAND gates.

    First, construct 60 NAND gates, following the given schematic and picture. I did this by cutting out 6x6 hole pieces of prototyping pcb board, and soldering all the components in according to the gate schematic. I then connected MALE pin connectors to the bottom of the gate. This way you can solder all the gates into the board to be connected in the following step. Make sure to test every single gate according to a NAND truth table, BEFORE you solder them onto the board, this will save a lot of headache trouble shooting in the future.

  • 2
    Assemble the board.
    Next, solder all the gates onto the two large prototyping pcb boards. Connect them using lengths of wire according to the schematic.
  • 3
    Troubleshoot

    This is the hardest part of the project. You just have to run the simulations in logisim, and test all the connections with a multimeter. As you can tell from the pictures, I had to jack in some more gates after some of gates I soldered in went bad.

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