Logic Gates and Logic Circuits:

Electronics circuits in computers, many new memories and controlling devices are made up of  thousands of Logic Gates. Logic gates take binary inputs and produce a binary output. Several logic gates combined together from a Logic Circuit and these circuits are designed to carry out a specific function. The checking of the output from a logic gate or logic circuit is done using a Truth Table.

Key Words:

  • Logic gate – the basic foundation of a digital circuit that controls the flow of electronic signals
  • Digital circuit – a circuit where electronic signals are one of two values, high voltage (1) or low voltage (0)
  • Voltage – the potential difference across an electrical component needed to make electricity flow through it
  • Microprocessor – an integrated circuit that provides the same functions of a cpu
  • Truth table – a way of showing every outcome of a logic gates

Types of logic gates:

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Truth Tables:

Truth tables are used to track down the output of logic gates or a circuit. For example the NOT Gate is the only gate to that only has one output and all the other gates have two outputs. Truth tables are constructed by binary values (computers can only read values of 1 and 0) which are used to make different combinations for different gates.

Boolean Expression:

All gates can be written in algebraic notation for example the AND gate can be written as A.B=Y which means A and B = Y.

. = the dot means AND Operation

+ = the plus means OR Operation

The line above the expressions means = NOT Operation

Logic Circuits:

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When Logic Gates are put together, they can carry out a function, the easiest method to make sure you’re doing it correct is to produce a truth table. In this truth table you should have the inputs, for example if there are only 2 inputs then you will only have the values ( 0 0 ) ( 1 0 ) ( 0 1 ) and ( 1 1 ) , the intermediate values (which are values which you get in the ‘middle’ or when you have a logic gate, they can be labelled any letter you want however do not repeat any letters) and output ( mainly written as X). When you have one input for example 0 1 into an AND gate, it will output 0, this 0 if there is no more gates left will be the output, if there is more, than it is an intermediate value.

Logic Circuits in real life can be found in any electronics, Air conditioners to T.V’s , however the amount of logic gates used can differ. Usually electronics will use as little logic gates as possible to carry out a function since this will reduce the price of the components and evidently leads to more profit for the owners.

Logic Building Blocks

You can use the NAND gate to make any gate you want, for example you can use the NAND gate to make an AND gate or even a XOR gate. This is what you call a building block.

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