Question

Show how a Half Adder would look like on a breadboard.

You may only use wires, resistors, LEDs, button switches, transistors, capacitors and a 9V battery as components. The logic gates must be done using various components and not with ICs, diodes or chips.

Either a drawing or a practical image works.

Answer 1

A Sum Half-Adder Circuit OUTPUT Carry Out - SUM XOR GATE CARRY AND GATE *OUT AND GATE

Below I am going to give you a step by step instruction of how to build a half adder using transistors as logic gates:

Below is the half adder circuit made from 2N7000 MOSFETs. The two LED's at the bottom left represent the answer to the math problem button 1 + button 2. The buttons are lined up above the 1's column and the LED on the left is the 2's column (can also be thought of as the carry bit).

NI GAGU yer 276-1583

So basically the a half adder is simply an XOR gate (the cluster of 8 transistors in a diamond formation at the lower part of the circuit) to calculate the value of addition between two 1 bit binary numbers. The carry bit is only set if both digits in the addition are 1's, so this is just simply an AND gate (the cluster of 4 transistors above the XOR gate).

Since all logic gates (NAND, AND, NOR, OR, XOR, NOT) can simply be made out of NAND gates, the adder can be broken up into a set of NAND gates:

A -

And since NAND gates are simply made out of two transistors, the adder can be broken down one more time into a set of transistors. In the circuit above I made each NAND gate out of 2 MOSFETs in the configuration below.

+V PPAI – Viss

NAND gates could also be made from bipolar NPN transistors:

xa A GND