2
\$\begingroup\$

LTspice has the following symbol for XOR gate:

enter image description here

But as far as I can see the XOR gate has two inputs.

\$\endgroup\$
  • 1
    \$\begingroup\$ Never look a gift horse in the mouth. \$\endgroup\$ – Andy aka Jun 12 '19 at 11:43
  • \$\begingroup\$ @Andyaka Their weird XOR has three terminals at the output. Very weird or do I.. \$\endgroup\$ – cm64 Jun 12 '19 at 11:46
  • \$\begingroup\$ The output with a circle is an inverting output, creating an XNOR gate. \$\endgroup\$ – Simon B Jun 12 '19 at 13:00
4
\$\begingroup\$

From LT wiki:

The reason that these gates are implemented like that is that this allows one device to act as 2-, 3-, 4- or 5- input gates with true, inverted, or complementary output with no simulation speed penalty for unused terminals.

and

The exclusive XOR device has non-standard behavior when more than two inputs are used: The output is true only when exactly one of all inputs is true. Use the associative property of XOR's with multiple XOR devices to implement an XOR block with more than two inputs.

|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ The thing is I was expecting two inputs and a single output. Now there are 5 inputs and 3 outputs. I just need to use this as a usual XOR but I dont know how to use the inputs and outputs with their XOR. Do you have any hint? It is not clear which terminal is output for instance there are three pins. \$\endgroup\$ – cm64 Jun 12 '19 at 11:45
  • 3
    \$\begingroup\$ Read the rest of the wiki entry. It's all there. If you just want a 2-input XOR, use the top two inputs and the top output. Connect the rest of the inputs to pin 8 (which should be grounded), and ignore the other output. \$\endgroup\$ – Dave Tweed Jun 12 '19 at 11:47
  • \$\begingroup\$ Just being a bit pedantic: you can use up to 5 inputs in any order, and unused inputs can be left floating, or connected to whatever other different net the 8th pin (ground pin) is connected (the floating inputs will automatically have the same connection). Also, it only has two outputs, complementary logic, not three. \$\endgroup\$ – a concerned citizen Jun 12 '19 at 18:29

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.