4 bit computer

The main goal of this paper is to assemble a simple 4 bit computer from four full adders. The adders used in the computer will consist of XOR and NAND gates. Their power consumptions will be measured and compared. The first part of the paper explains the theory behind the basic functionality of a bipolar NPN transistor and the logic gates required to construct a full adder. The following part consists of schematics which were used in the final production of the computer. NAND adder, XOR adder and result schemes were made using printed circuit board. Virtual logic gate tests were made to understand the theory behind the pull-up and pull-down resistors. Tests were made with a virtual electric circuit emulator. Tests were conducted firstly with the correct logic gate structure. Then various alterations were made for the components to test how the electricity will flow. Assembly of full adders was done in three ways. To test out components and logic gate circuits, a XOR full adder was made on a breadboard. Firstly, the smaller gates like AND and OR were were assembled separately. Then they were combined into a bigger XOR gate followed by an another one and then combined into the final circuit. Second XOR adder was assembled using a mounting plate. The whole process took a lot of time and the end result didn't work due to manufacturing errors. Final four adders were made using printed circuit boards with photoresist transfer method. XOR adders power consumption is higher than NAND adders. NAND adder power consumption doesn't increase or decrease with the amount of given inputs and it stays ON even if it has no inputs. The XOR adders consumption increased with the amount of input it was given. If none, then the consumption was almost zero