DIODES
What are Diodes?
Diodes are used to protect circuits by limiting the voltage and to also transform AC into DC. Semiconductors like
silicon and germanium are used to make the most of the diodes. Even though they transmit current in a single direction,
the way with which they transmit differs.
Furthermore, you also know that diodes are electronic components that allow current to flow in one D. direction. Most
diodes these days made from two of the most popular semiconductor materials in electronics-silicon or germanium.
Diode Polarity
Diodes are polarized components, meaning they have a very specific orientation that needs to be
connected in a circuit to work correctly. On a physical diode, you'll notice two terminals
extending from a tin can shape in the middle.
One side is the positive terminal, called the anode. The other terminal is the negative end, called
the cathode. Current can only move in a diode from the anode to the cathode, never the other
way around.
There are two ways to describe how current will or won't flow through a diode:
1. Forward-Biased: When you insert a battery correctly into a circuit, current will be allowed to flow through a diode;
this is called a forward-biased state.
2. Reverse-Biased: When you slip a battery into a circuit backward, your diode will block any any current from flowing,
which is called a reverse-biased state.
In a standard diode, forward biasing occurs when the voltage across a diode permits the natural flow of current, whereas
reverse biasing denotes a voltage across the diode in the opposite direction.
Types of Diode
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Standard Diodes
Rectifier Diodes
Schottky diode
Zener diode
Photodiode
Light-Emitting Diodes (LEDs)
1. Standard Diodes
Your average diode. Standard diodes have a moderate voltage
requirement and a low maximum current rating.
2. Rectifier Diodes
These are the beefier siblings of the standard diodes and have a higher maximum current rating and
forward voltage. They are mainly used in Power supplies.
3. Schottky Diode
This is the quirky cousin of the diode family. The Schottky diode comes in handy when you need to
limit the voltage loss in your circuit. You can identify a Schottky diode on a schematic by looking for
your typical diode symbol by adding two new bends ('S' shape) on the cathode pin.
4. Zener diode
The Zener diodes are the black sheep of the diode family. They send electric current flowing in the
opposite direction! They do this by taking advantage of the breakdown voltage discussed above, also
called the Zener Breakdown. By taking advantage of this breakdown ability, Zener diodes are great
at creating a stable reference voltage at a specific spot in a circuit.
5. Photodiode
Photodiodes are the rebellious teenagers of the diode family. Rather than simply allowing current to
flow through a circuit, photodiodes capture energy from a light source and turn it into electrical
current. You'll find these for use in solar panels and optical communications.
6. Light-Emitting Diodes (LEDs)
LEDS are the shining stars of the diode family. Like standard diodes,
LEDs only allow current to flow in one direction, but with a twist!
When the proper forward voltage is applied, these LEDs light up with
brilliant colors. Though, specific colors of a LED require different,
forward voltages. For example, a blue LED requires a forward voltage
of 3.3V, whereas a red LED only needs 2.2V to start shining.
The LED or the lamp in the circuit glows when the negative end or
cathode of a diode is connected to the negative terminal of the battery
and its anode to the positive terminal.
What makes these LEDs so popular?
Efficiency: LEDs make light electronically without pumping out a ton of heat like traditional incandescent light
bulbs. This allows them to save a ton of energy.
 Control: LEDs are also super easy to control in an electronic circuit. As long as they have a resistor placed before
them, then they're bound to work!
 Inexpensive: LEDs are also very affordable and last. That's why you'll find them used so much in traffic signals,
displays, and infrared signals.