Talk:XOR gate
Building XOR
is it possible to build an XOR gate from less than 4 NAND gates? Pjbeierle (talk) 22:55, 14 April 2010 (UTC)
Implementation
This page should show a transistor implementation of an xor gate. Fresheneesz 02:08, 19 October 2006 (UTC)
- Agreed. Although whether TTL or CMOS would be better, I'm not sure. I'd prefer CMOS because MOSFETs are easier to understand than bipolar transistors, but more people are familiar with bipolars... 87.75.164.162 21:09, 19 October 2006 (UTC)
XOR Gate Constructed Using Only NOR Gates - image
Doesn't the schematic actually depict a XNOR gate instead of a XOR gate like it should be?? maybe it's just to late. 130.88.165.70 05:15, 23 January 2007 (UTC)
I was thinking the same thing as "130.88.165.70 05:15, 23 January 2007 (UTC)" - that picture should have another NOR gate at the end. But I'm pretty new to the whole gate concept
Three inputs revisited dfsfsfsdfdsfd
That last edit was foolish. Exclusive or is not universally defined to give parity. Its definition is disputed. --ToobMug 16:38, 22 April 2007 (UTC)
Unique Properties
Xor has very interesting properties that give it very unique uses, and it would be relevant to mention these applications. For instance, since A^A = 0, xor can identify any numbers that are not duplicated given a string of integers (ie. A^B^C^A^B = C). Also, since A^B=C implies that C^B = A, it can be exploited to create a doubly linked list in which only one pointer is needed per node. Xor is also often used in simple cryptography appications. User:ypg1988 19:52, 3 October 2007 (UST)
Cryptography
I agree with ypg1988: this article should explain the use of XOR in cyptography.
Also, in case anyone feels like making another one of those diagrams, here's another way to make XOR logic out of other types of gates:
>>====OR--------------\
...\\...................................---AND----->
....\\===AND----NOT---/
how does xor gate function with cmos? —Preceding unsigned comment added by 41.204.170.69 (talk) 10:11, 16 October 2009 (UTC)
I added a circuit diagram for a cmos xor --Wikidood123456789 (talk) 10:14, 7 January 2010 (UTC)
Why is that CMOS?
I'm referring to the example CMOS implementation of an XOR gate.
On CMOS it says "The main principle behind CMOS circuits [...] to create paths to the output from either the voltage source or ground." But when both A and B are not set, there is no path from the output to the ground. So why is this still considered a CMOS circuit? 88.73.98.31 (talk) 08:31, 16 January 2010 (UTC)
I think you're right. In order for this to be a CMOS XOR gate, transistor connected to Vcc needs to be p-type, making the right two transistors into an inverter. 76.126.57.22 (talk) 05:13, 20 January 2010 (UTC) The bit on the right with 2 transistors is an inverter. —Preceding unsigned comment added by Wikidood123456789 (talk • contribs) 17:29, 5 February 2010 (UTC) im wondering if he vcc could be connected with to diodes to the inputs. Wikidood123456789 (talk) 17:36, 5 February 2010 (UTC) i see now it is a p-type mosfet with a differrent symbol i can upgrade the picture Wikidood123456789 (talk) 18:34, 5 February 2010 (UTC)
I would criticize this picture as being unnecessarily complex-looking. If you pull it apart it is easier to understand: just two pass transistors and a transmission gate (with an inverter for making ~A) —Preceding unsigned comment added by 136.152.148.147 (talk) 00:42, 13 March 2010 (UTC)
- I've been looking at that schematic as well - there are a number of problems with it. The fact that the output is undefined when the inputs are floating is not a problem in itself - logic circuits are only ever defined when the inputs are. This is true for CMOS where a floating input is meaningless, although TTL avoids the problem by defining a floating input as high.
- The problems I see are the schematic doesn't actually work. When A = 1 and B = 0 the output is linked to the A input, and any current drawn from the output is passed straight through to A. That limits the depth of logic you can implement and also has implications for fan out.
- Worse, when A = 0 and B = 1 the B input is connected to VCC. That means that whatever is driving that input is then unable to alter that input since the circuit is driving it itself. Sicne the only reference for this schematic points ot a simualtor as if to say "try it for yourself" (which is inherently OR anyway) I suggest it should be deleted. Crispmuncher (talk) 21:57, 25 June 2010 (UTC)
- The circuit implements the XOR function and it is CMOS - CMOS stands for Complemantary Metal Oxide Semiconductor. That means a CMOS circuit will use both nMOS and pMOS type transistors. What this circuit is, it's a pass transistor logic gate. And by the way, if you consider this circuit as part of a more complex system, its behaviour is according to the quote from the CMOS article "create paths to the output from either the voltage source or ground". If you consider the inputs of the gate generated by another CMOS gate (but not a pass transistor gate), the output will still be connected to either ground or power line for all input combinations, only that it's not connected inside this gate but on a previous one.212.77.163.102 (talk) 14:55, 30 September 2010 (UTC)Apass
Minimal implementation
Should we not mention the minimal three gate XOR gate? The inputs may be connected to a pair of AND gates with one inverting input each, and the outputs of those combined via an OR gate. The AND gate with an inverting input may not be a widely recognised gate but inverting an input in CMOS (and and most other logic families) is a simple re-wiring job, free in terms of components and area. Crispmuncher (talk) 21:57, 25 June 2010 (UTC)