Книга: Introduction to Microprocessors and Microcontrollers

What decides the output voltage?

We connect one or more voltages to the input of the gate. These input voltages are either logic 0 or logic 1 levels. The logic gate looks at the input voltages and ‘decides’, depending on its design, what voltage to produce at the output of the circuit.

There are only four basic designs of gate. They are called the NOT gate, the AND gate, the OR gate and the XOR gate. Notice how we use capital letters for the names of the gates otherwise we can finish up with some almost indecipherable sentences. Not not or and not and or not…

A little reminder before we start. Logic gates are clever little chaps but they are not magic. Just like any other electronic circuit, they need power supplies to make them work. Now, because all gates and microprocessors need power supplies, we tend to assume that everyone knows that. You will notice that power supplies are not shown in any of the diagrams in this chapter but that doesn’t mean that they are not there!

We will explore these gates now, starting from the simplest.

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