Buffer

Buffer truth table
Input	Output
A	A
0	0
1	1

ANSI buffer gate symbol

A digital buffer (or a logic buffer) is an electronic circuit element used to copy a digital input signal and isolate it from any output load.

Types

Single input voltage buffer

Available in both Inverting and Non-Inverting buffers, these devices are simple in nature and are the building blocks of larger integrated circuits.

Tri-state digital buffer

Tri-state buffers differs from the single input voltage buffer in that there are two inputs to the circuit, a data input and a control input. A control input is similar to that of a valve, controlling the flow of information from the data input to the output. There are two different modes of control inputs, Active High and Active Low. When the control pin is not in it's active state, the circuit's output operates in a mode of high impedance otherwise known as "Hi-Z".

Active high tri-state buffer

Non-Inverting, Active High
Input	Control	Output
0	0	Hi-Z
1	0	Hi-Z
0	1	0
1	1	1

Inverting, Active High
Input	Control	Output
0	0	Hi-Z
1	0	Hi-Z
0	1	1
1	1	0

Active low tri-state buffer

Non-Inverting, Active Low
Input	Control	Output
0	0	0
1	0	1
0	1	Hi-Z
1	1	Hi-Z

Inverting, Active Low
Input	Control	Output
0	0	1
1	0	0
0	1	Hi-Z
1	1	Hi-Z

See also

• Inverter
• AND gate
• OR gate
• NAND gate
• NOR gate
• XOR gate
• XNOR gate
• IMPLY gate
• NIMPLY gate