In the previous lessons, we learned about the logic gate “AND” and “OR”. The “AND” logical operation produces a “High” output if all of its input are “1s”. If one or multiples of its inputs are “0s”, the output of the “AND” logic gate will be a zero. The “OR” logical operation produces a “Low” output if all of its input are “0s”. If one or multiples of its inputs are “1s”, the output of the “OR” logic gate will be a “1”. The “NOT” gate is a very simple gate and its implements the negation operation. The “NOT” gate has one input and one output. The “NOT” gate is often called the inverting gate and will invert the input. If the input is Low “0”, the output is gonna be High “1”. If the input is High “1”, the output is gonna be Low “0”. You can find the symbol of the “NOT” gate below :
Below, you can find the 2 possible input with its output result :
Truth table
A truth table is often used to describe how a logic gate behave with given inputs. For the “NOT” logic gate, we have the following truth table :
For the “NOT” gate, the important things to remember is that the output is the inversion of the input. Do note that there is a circle (often called inversion bubble) on the output which indicates the inverting effect of the gate. This circle can sometimes be found on others gates to indicate the same effect. We will eventually see this in later lessons on the “NAND” and “NOR” gates. We have completed the lesson on the “NOT” gate. We will reuse this logic gate when combining it with others logic gate. In the next lesson, we will start to explore how we can connect theses three gates together (“AND”, “OR” and “NOT”) and analyse some circuits.