I searched in the "List of 7400 series integrated circuits" on Wikipedia for a open-collector OR-gate, but couldn't find any.

The list looks complete, so I assume there is no such chip in the 7400 series.

Why is there no open-collector OR-gate in the 7400 series?


closed as primarily opinion-based by Olin Lathrop, Bruce Abbott, Enric Blanco, PeterJ, laptop2d Jun 2 '17 at 14:44

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ There was never sufficient commercial demand to create such a special-purpose part. \$\endgroup\$ – Dave Tweed May 27 '17 at 23:26
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    \$\begingroup\$ As @DaveTweed said there is very little demand. Open-collector parts are only used rarely - they are mainly for interfacing to non-logic gates. OR gates are also not used very much - in 40 years of designing digital circuitry I have never designed them in. The combination of the two is more rarely required. \$\endgroup\$ – Kevin White May 28 '17 at 0:28
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    \$\begingroup\$ An application of open-collector gates was driving a bus structure, where an idle bus was pulled high by resistors. NANDs have an advantage over NORs, because one input is used as enable while the other input is used as data. Tri-state bus buffers were introduced later. \$\endgroup\$ – glen_geek May 28 '17 at 2:39
  • \$\begingroup\$ Only the people that created the 7400 series eons ago could answer this. Everyone else is just guessing at reasons they might have made the decisions they did. Closing this pointless opinion-based question. \$\endgroup\$ – Olin Lathrop May 28 '17 at 13:11

I don't genuinely know the answer to your question, but I can speculate that it's because there are (quad) open-collector NAND and NOR gates, which are universal gates, and you can relatively easily synthesize an open collector OR gate from these. For example:


simulate this circuit – Schematic created using CircuitLab

Because, of course, A NOR 0 = ~A and ~(A NOR B) = A OR B


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