Semiconductor & Computer Engineering
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| − | A '''buffer''', is a basic [[logic gate]] that passes its input, unchanged, to its output. It's 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 | + | A '''buffer''', is a basic [[logic gate]] that passes its input, unchanged, to its output. It's 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 == | ||
Revision as of 10:01, 18 March 2016
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A buffer, is a basic logic gate that passes its input, unchanged, to its output. It's 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
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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 input. In most technologies, a buffer is made of two inverter back-to-back. One of the many purposes for a buffer is to generate weak output from non-restoring logic that was used.
Design
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This section is empty; you can help add the missing info by editing this page. |
Symbolic representation
Buffers are typically drown on schematics using one of a standard symbol. Below are three of the commonly found standard symbols.
| ANSI | IEC | DIN | British |
|---|---|---|---|
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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
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This section is empty; you can help add the missing info by editing this page. |
4000 series chips
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This section is empty; you can help add the missing info by editing this page. |
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
