Electronics Fundamentals: Diode D and Transistor T

last updated: 15/01/19


Song of this chapter: Darren Korb > Transistor: Original Soundtrack of the game

Electricity’s one-way street

Diode (wiki)


Symbol of a diode, a light emitting diode (LED) and a Zener diode (Z-diode):

symbol diodesymbol diode LEDsymbol Z-diode

In the last decades electronics moved dramatically from analogue to digital. Two elementary digital circuits are the OR and AND gate. We will use the positive logic, so the two digital states true and false will be represented with HIGH (1, +5 V or +3.3 V) and LOW (0, 0 V) (we will use the Arduino notation) Two inputs of the gate gives 2² = 4 possibilities or cases (3 inputs would give 2³ = 8 cases).

Logic OR is only false if none of the conditions are fulfilled. If I drink water OR lemonade I won't be thirsty any more. It's not an exclusive OR because I can also drink both drinks, even mixed :).

case B A Z        case B A Z
1 false false true        1 0 0 0
2 false true true        2 0 1 1
3 true false true        3 1 0 1
4 true true true        4 1 1 1

Logic AND is only true if both conditions are fulfilled. If I have money AND my girlfriend has time we will go to the cinema.

case B A Z        case B A Z
1 false false false        1 0 0 0
2 false true false        2 0 1 0
3 true false false        3 1 0 0
4 true true true        4 1 1 1
"Just do it" D1:

OR gate with diodesAND gate with diodes

Rectifier (wiki)

Light-emitting diode (wiki)

Zener diode (wiki)