Exceedingly Simple XOR Gate

Discussion in 'General Electronics Chat' started by IsquaredC, Mar 3, 2012.

  1. IsquaredC

    Thread Starter New Member

    Nov 28, 2011
    I've always been facinated with the concept of minimization in electronics, whether it's simplifying things like Boolean expressions or finding new ways to reduce component #'s in integrated circuit designs. I tried to apply these minimization techniques on a relatively component-heavy logic gate (XOR gate) and this is what I came up with (Thumbnail below). All-in-all, it uses four diodes, two resistors, and one PNP transistor. (Which I assume makes this a DTL circuit). This circuit uses a rectifier to separate the A and B inputs when one is zero and the other is one to allow current to pass through the base of the transistor, changing Q to 1. Are there even simpler XOR gate designs out there? And also, are rectifiers typically used in digital logic circuits or are they more exclusively used for rectifiying AC in things like power supplies?
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    Here is a 3 transistor XOR. It is probably best implemented inside an IC.
  3. hobbyist

    Distinguished Member

    Aug 10, 2008
    Your circuit looks good, and will work properly.

    However one note about it, the strength of the output current is the direct result of the input current through the diode and PNP transistor.

    This could cause eratic behavior, it is best to keep the outputs and inputs currents seperate from eachother.
    So the output is consistent in current flow regardless how big or small the input signal strength is.

    Here is one solution, to that kind of dilemna.
    Better solutions would involve more components for even better stability.

    In actuality the 2 inputs should have pull down resistors to ground as also.

    Xor gate.jpg

    Yes diodes are used in digital circuitry as well as rectifiers in analog circuits.

    Digital circuits they are refered as steering diodes.
    Last edited: Mar 4, 2012
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