XNOR gate
An XNOR (exclusive NOR) gate’s output is 1 when its inputs are the same and 0 when they differ. Its symbol is the XOR gate’s shape with a small circle at the output.
Easily confused with
- XOR gateAn XOR (exclusive OR) gate’s output is 1 when its inputs differ and 0 when they are the same. Its symbol is the OR gate’s shape with a second curved line behind its back.
- NOR gateA NOR gate is an OR gate with its output inverted: the output is 1 only when all inputs are 0. Its symbol is the OR gate’s shape with a small circle at the output.
How to read it
Kuphaldt’s Lessons in Electric Circuits describes the XNOR gate as an exclusive-OR gate with an inverted output: its output is high whenever both inputs are at the same logic level, 00 or 11. In Boolean algebra it is an XOR with a bar over the whole expression: Texas Instruments’ data sheet for the CD74HC7266, four 2-input XNOR gates, gives each gate’s function as A ⊕ B with the bar across it.
Also searched as: ENOR, equivalence gate, exclusive NOR, XNOR gate symbol, XNOR truth table.
Truth table
| A | B | Y = NOT (A ⊕ B) |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
The two standard shapes
Distinctive shape ANSI/IEEE Std 91: the XOR shape with a circle. Rectangular shape IEC 60617-12: a box marked =1, with a circle at the output.
The rectangular form is the XOR box, marked =1, with the negation circle at the output. Texas Instruments’ guide to IEEE Std 91 also lists =, logic identity, for an element whose inputs must all stand at the same state; for two inputs that is the XNOR rule.
Look-alikes
The XOR gate is the same shape without the circle. The NOR gate has the circle but only one curved line at the back.
Read next
- Next in Logic gate symbolsBuffer gateA buffer passes its input straight through: 1 gives 1 and 0 gives 0. Its symbol is a triangle with no circle; a buffer strengthens a signal’s drive without changing its logic.
- The same shape in Air Force ranksChief master sergeant (E-9)Chief master sergeant, pay grade E-9: the highest of the senior noncommissioned officer ranks in the US Air Force. The insignia is five stripes below a star in a circle and three stripes above it.
More logic gate symbols
The same shape elsewhere
Browse symbols drawn with circles, curves and waves or lines.
Sources
- Lessons In Electric Circuits, Volume IV: Digital, chapter 3, Logic Gates, Tony R. Kuphaldt, open textbook (Design Science License), Tony R. Kuphaldt (ibiblio), The Exclusive-NOR gate
- Overview of IEEE Standard 91-1984: Explanation of Logic Symbols, SDYZ001A, 1996, Texas Instruments, Table 1; Table 2
- CDx4HC7266 Quadruple 2-Input XNOR Gates (data sheet), CD74HC7266 data sheet, Texas Instruments, 3 Description
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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