Logic Gate
From bildr
Overview
A logic gate is a method for evaluating discrete values where an input is reduced to a specific output. Logic gates serve a valuable function in digital circuit, allowing the use of boolean logic. Gates are commonly constructed from a network of diodes and/or transistors, but a variety of other methods such as relays exist. Basic functions can be modeled using AND and OR gates. Using an inverter (NOT gate), various other gates can be modeled, such as NAND, NOR, XOR, and XNOR gates.
Technical Information
The possible outcomes of logic gates can be pre-determined through the use of truth trables. However, these values are not efficient and grow exponentially with complexity of the circuit. A wide variety of algorithms exist for minimizing complexity, such as the Quine–McCluskey algorithm.
The most simplistic gates with diodes. However, only AND and OR gates can be created. However, using transistors, NOT gates can be created. any other gate type can be constructed solely from NAND or NOR gates, but with added complexity as a result.
Below is an example of how 2 input values can have 16 different possible outcomes depending on the boolean function used.
| INPUT | A | 0 | 0 | 1 | 1 | Meaning |
| B | 0 | 1 | 0 | 1 | ||
| OUTPUT | FALSE | 0 | 0 | 0 | 0 | Whatever A and B, the output is false. Contradiction. |
| A AND B | 0 | 0 | 0 | 1 | Output is true if and only if (iff) both A and B are true. | |
| A \not\rightarrow B | 0 | 0 | 1 | 0 | A doesn't imply B. True iff A but not B. | |
| A | 0 | 0 | 1 | 1 | True whenever A is true. | |
| A \not\leftarrow B | 0 | 1 | 0 | 0 | A is not implied by B. True iff not A but B. | |
| B | 0 | 1 | 0 | 1 | True whenever B is true. | |
| A XOR B | 0 | 1 | 1 | 0 | True iff A is not equal to B. | |
| A OR B | 0 | 1 | 1 | 1 | True iff A is true, or B is true, or both. | |
| A NOR B | 1 | 0 | 0 | 0 | True iff neither A nor B. | |
| A XNOR B | 1 | 0 | 0 | 1 | True iff A is equal to B. | |
| NOT B | 1 | 0 | 1 | 0 | True iff B is false. | |
| A \leftarrow B | 1 | 0 | 1 | 1 | A is implied by B. False if not A but B, otherwise true. | |
| NOT A | 1 | 1 | 0 | 0 | True iff A is false. | |
| A \rightarrow B | 1 | 1 | 0 | 1 | A implies B. False if A but not B, otherwise true. | |
| A NAND B | 1 | 1 | 1 | 0 | A and B are not both true. | |
| TRUE | 1 | 1 | 1 | 1 | Whatever A and B, the output is true. Tautology. |
This page is an Article on bildr. Articles are pages that define or explain a concept, method, or generic item.