Semiconductor & Computer Engineering
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| − | A '''buffer''', is a basic [[logic gate]] that passes its input, unchanged, to its output. | + | 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 == | == Description == | ||
{{expand section}} | {{expand section}} | ||
| − | A buffer is a very basic active device that generates an output identical to its | + | 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 [[inverter]]s back-to-back. One of the many purposes for a buffer is to regenerate weak output from [[non-restoring logic]]. |
==Design== | ==Design== | ||
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== Symbolic representation == | == Symbolic representation == | ||
| − | Buffers are typically | + | Buffers are typically drawn on schematics using one of a standard symbol. Below are three of the commonly found standard symbols. |
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=== [[4000 series]] chips === | === [[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<sub>DD</sub> 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<sub>DD</sub> and GND, 12 pins are used for the 6 independent buffers. Pins 13 and 16 are not connected. Both chips implement the expression Q<sub>N</sub> = A<sub>N</sub> | The 7407 is a TTL chip with 14 pins. Two pins are used for V<sub>DD</sub> 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<sub>DD</sub> and GND, 12 pins are used for the 6 independent buffers. Pins 13 and 16 are not connected. Both chips implement the expression Q<sub>N</sub> = A<sub>N</sub> | ||
Latest revision as of 15:15, 11 August 2018
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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.
Contents
Description[edit]
 |
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[edit]
| |
This section is empty; you can help add the missing info by editing this page. |
Symbolic representation[edit]
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 |
|---|---|---|---|
| |
.svg){kind=small} |
.svg) |
.svg)
|
Implementations[edit]
A buffer can be implemented in variety of of technologies.
CMOS[edit]
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[edit]
Various buffers/drivers exist chips as well for both 7400 series and 4000 series.
7400 series chips[edit]
| |
This section is empty; you can help add the missing info by editing this page. |
4000 series chips[edit]
-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 VDD 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 VDD and GND, 12 pins are used for the 6 independent buffers. Pins 13 and 16 are not connected. Both chips implement the expression QN = AN
7407 Hex Buffer/Driver
4050 CMOS Hex Buffer/Driver
