How Transistors Work - The Learning Circuit

NPN 2N2222 transistor component as switch circuit with schematic tutorial. 2N2222A

How to Use an NPN Transistor to Switch on an LED - Electronics for Absolute Beginners

Using a Transistor as a Switch

Transistors as a Switch: Theory & Explanation

How to use transistors as a switch - NPN and PNP - Active High and Active Low

Making logic gates from transistors

Digital Logic Gates from Transistors, AND, NAND, OR, NOR, XOR, XNOR, Buffer, and Inverter