Buffer gate
A 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.
Easily confused with
How to read it
Kuphaldt’s Lessons in Electric Circuits describes the buffer as a gate made to do the work of two inverters in a row: the logic level is unchanged, but a weak signal that can’t source or sink much current comes out able to drive a load. Its symbol is a triangle with no inverting bubble on the output. Texas Instruments’ guide to IEEE Std 91 lists a buffer as an element with more than usual output capability, and its SN74LVC1G34, a single buffer gate with high output drive, performs the Boolean function Y = A.
Also searched as: buffer symbol, buffer truth table, non-inverting buffer, triangle gate.
Truth table
| A | Y = A |
|---|---|
| 0 | 0 |
| 1 | 1 |
The two standard shapes
Distinctive shape ANSI/IEEE Std 91: a triangle. Rectangular shape IEC 60617-12: a box marked 1.
Tri-state buffers
A tri-state buffer has an extra input, the enable, and three output states: high, low, and floating (high-Z), Kuphaldt explains. Texas Instruments’ IEEE Std 91 guide gives the 3-state output its own symbol inside the outline.
Look-alikes
The NOT gate is the same triangle with a small circle at the tip, and inverts.
Read next
- Next in Logic gate symbolsInversion bubble (negation circle)The small circle on a logic gate’s input or output means inversion: the signal is flipped from 1 to 0, or 0 to 1, at that point. It turns AND into NAND, OR into NOR and a buffer into an inverter.
- The same shape in African flagsFlag of the ComorosThe Comoros flag is four horizontal stripes, yellow, white, red and blue from the top, with a green triangle along the pole holding a white crescent and four white stars in a line between its tips. Norway’s Store norske leksikon explains the crescent as the symbol of Islam and the four stars as the four islands of the Comoros; Lex says the four stripes are said to stand for the islands too.
More logic gate symbols
The same shape elsewhere
Browse symbols drawn with lines or triangles.
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 buffer gate; Tristate outputs
- Overview of IEEE Standard 91-1984: Explanation of Logic Symbols, SDYZ001A, 1996, Texas Instruments, Table 1; §3.3 and Table 3
- SN74LVC1G34 Single Buffer Gate (data sheet), SN74LVC1G34 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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