The AND gate is the second of the three elementary gates, and its operation is illustrated below.Īs the truth table shows the AND gate has an output of zero unless all of its inputs are at one. While it may indeed be a simple gate the NOT gate is very useful, as inverting a digital signal is a common requirement when designing logic circuits. The boolean algebra description of the NOT gate is also shown, the line above the “Y” indicates that the output is inverted. The output of the NOT gate is the inverse of its input, in other words, it changes zeros into ones and ones into zeros. This type of gate is sometimes referred to as an “Inverter”, and from the truth table, it’s easy to see why. It is the first of the three elementary gates. The NOT gate is the simplest of all the gates, it is also the only gate that only has one input.

We’ll examine that gate, and six others, right now. Incidentally, the above truth table is for an “Exclusive OR” gate. When both inputs are one then the output is zero.īy looking at the truth table you can determine the logic of the gate.When the inputs to our gate are both zero the output is zero.The inputs to our gate are labeled “A” and “B”, and the output is labeled “Y”. The relationship between the input and output logic levels on a gate can be best illustrated using what is known as a “truth table”.Ī truth table is a table or chart that lists all of the possible input combinations and the resulting output logic level. It uses the rules of boolean algebra to determine the output condition. The gate will set its output to either zero or one, based upon the state of the input signals. There are three fundamental gates and a total of seven basic logic gates (plus a number of derivatives).

Actually, they are composed of basic gates.Ī “basic gate” is defined as a component with one or more inputs and one output. While these devices are certainly elementary digital “building blocks” they are not basic gates. When you examine a catalog of basic digital components you’ll run across devices with interesting names like “monostable multivibrators” or “edge-triggered flip-flops”. You’ll be able to troubleshoot existing circuits and you’ll also gain a better understanding of the inner working of modern electronic components. They can also be used along with CPU’s and MCU’s to create very complex designs or to simplify programming.Įven if you don’t design our circuits using basic gates you can still benefit from learning about them. For simple circuits, they can offer both cost and performance advantages. That thought is incorrect.īasic logic gates are still widely used, both with and without microcontrollers. With the availability of inexpensive microcontrollers, one might think that basic logic gates are no longer used for new designs.

Just as simple atoms form molecules which in turn can form crickets, elephants, or people, basic gates are the underlying foundations of all digital electronic devices and components. Microcontrollers and microprocessors use thousands, even millions, of these gates. And these signals are modified using basic logic gates. Our digital devices use two distinct voltage levels to represent zeroes and ones. Unlike analog signals, which can exist at an infinite number of levels, digital signals exist at only two levels – zero and one. Our radios, televisions, and audio equipment are no longer analog devices, we all own computers and smartphones, and our appliances and even our light bulbs are now microcontroller-based. We live in a world whether virtually everything is digital. Future articles and videos will expand our coverage to other, more complex, logic gates. We will examine the most basic of these devices today.

Logicbots tutorial