Buffer Gate

ANSI Symbol

Functional

Truth Table

Inputs Outputs A Q 0 0 1 1

Other Gates Buffer TriBuffer NOT AND OR XOR NAND NOR XNOR Trans AOI OAI MAJ INH IMPLY NIMPLY

Other Components Plexers MUX DEMUX Encoder Decoder Pri-Encoder ALU Adder Subtractor Multiplier Divider Shifter Rotator MAC Comparator Negator Memory D latch D flip-flop SR latch JK flip-flop T flip-flop Register Register file SRAM Counter ROM CAM DRAM I/O Shift register SIPO PISO ADC DAC

A buffer, is a basic logic gate that passes its input, unchanged, to its output. Its behavior is the opposite of a NOT gate. The main purpose of a buffer is to regenerate the input, usually using a strong high and a strong low. A buffer has one input and one output; its output always equals its input. Buffers are also used to increase the propagation delay of circuits by driving the large capacitive loads.

Description

This section requires expansion; you can help adding the missing info.

A buffer is a very basic active device that generates an output identical to its input. In most technologies, a buffer is made of two inverters back-to-back. One of the many purposes for a buffer is to regenerate weak output from non-restoring logic.

Design

This section is empty; you can help add the missing info by editing this page.

Symbolic representation

Buffers are typically drawn on schematics using one of a standard symbol. Below are three of the commonly found standard symbols.

ANSI	IEC	DIN	British

Implementations

A buffer can be implemented in variety of of technologies.

CMOS

A CMOS buffer gate with one input and one output can be realized as simply two inverters back to back - built out of just 4 gates.

The table on the right shows the states of the four transistors with the various inputs of A.

Buffer Gate by Transistor
A	Q1	Q2	Q3	Q4	Q
0	1	0	0	1	0
1	0	1	1	0	1

Discrete Chips

Various buffers/drivers exist chips as well for both 7400 series and 4000 series.

7400 series chips

This section is empty; you can help add the missing info by editing this page.

4000 series chips

-CD4050 NonInverting 6 Channel (THE Jellybean go-to part for many people. This is often used as a 5 volt to 3.3 volt, voltage level shifter in hobby electronics for displays and sensors)

-CD4049 Inverting version of the CD4050.

-HEF40244 NonInverting 8 channel with 2 independently selected (4 channels each) tristate enable lines. This IC also has the advantage of inputs and outputs on opposing sides of the chip pin for pin.

The 7407 is a TTL chip with 14 pins. Two pins are used for V_DD and GND, the other 12 pins are used for the 6 independent buffers. The 4050 is a CMOS Hex Buffer with 16 pins. Two pins are used for V_DD and GND, 12 pins are used for the 6 independent buffers. Pins 13 and 16 are not connected. Both chips implement the expression Q_N = A_N

• 

  7407 Hex Buffer/Driver

• 

  4050 CMOS Hex Buffer/Driver