Half Adder using transistors

The Half Adder is a digital circuit that adds two single binary digits. It has two inputs and two outputs (sum and carry). The carry signal represents an overflow into the next digit in a multi-digit addition.
The XOR gate can be built using a combination of XOR and AND gates.
The full truth table, showing all input and output states, can be found below. Each row represents a physical state of the circuit.

Truth table

Input A	Input B	Sum S	Carry C
0	0	0	0
0	1	1	0
1	0	1	0
1	1	0	1

Logic scheme

The inputs and outputs in the scheme correspond to the truth table headers.

Implementation

For the implementation, NPN 2N2222A transistors were used.