Semiconductors, diode, transistor
https://www.youtube.com/watch?v=ar7xDMR4P_U
https://www.youtube.com/watch?v=IcrBqCFLHIY
https://www.youtube.com/watch?v=JBtEckh3L9Q
https://www.youtube.com/watch?v=4ozD_5WRWNk
www.youtube.com/watch?v=DXvAlwMAxiA+
https://www.youtube.com/watch?v=QLYSGrbA09w
https://www.youtube.com/watch?v=QO5FgM7MLGg
https://www.youtube.com/watch?v=7ukDKVHnac4
