Diodes, Types and Functions in Electronic Circuits

By | September 7, 2021

Diode (Diode) is a component made of semiconductor material and has a function to conduct electric current in one direction but inhibit electric current from the opposite direction. Because of its properties that can conduct electric current in one direction (forward bias) and inhibit electric current from the opposite direction (reverse bias), diodes are often used as rectifiers or power supplies.

Semi-conductor materials that are often used to make diodes are silicon (Si) and germanium (Ge) materials. Diodes generally have 2 electrodes (terminals), the anode (+) and cathode (-) and have a working principle based on semi-conductor p-n junction technology, which is to allow current to flow from the p-type side (anode) to the n-type side (cathode). ) but cannot conduct current in the reverse direction.

The positive side (P) is called the anode and the negative side (N) is called the cathode. The diode symbol is like an arrow that goes from the P side to the N side.
Diode Symbol
In an electronic circuit there are several diodes of different types. Where each type of diode has a role and function that is not the same as each other, both in signal processing, current and voltage. So it is important for you to know all the types of diodes and their uses in various electronic circuits.

Types of Diodes and  Functions

Basically, the diode has a function to conduct electric current in one direction (forward bias) and inhibit electric current from the opposite direction (reverse bias). However, when viewed further, the functions possessed by diodes are many, depending on the type of diode used, such as lighting, current control, signal detector, and so on.
The existence of components made of this semiconductor material, almost always exists in all electronic circuits, be it simple circuits or complex circuits. Speaking of materials, the diode itself is divided into two main materials used in the manufacturing process, namely Silicon (Si) and Germanium (Ge).
Each of these semiconductor materials has an unequal voltage drop, namely the silicon diode has a voltage drop of 0.7 volts, while the germanium diode has a voltage drop of 0.4 volts.

Here are the types of diodes and their uses in electronic circuits.

1. Rectifier Diode

Rectifier diode is a diode with the basic construction of P and N junction (PN Junction). As the name implies, this diode functions as a rectifier for AC to DC voltage in a power supply. Rectifier diodes are also known as “normal diodes”.

Rectifier Diode

Rectifier Diode Symbol

There are 3 main configurations of a diode when used as an AC surge rectifier. They are half wave rectifier, full wave rectifier and full wave rectifier with a bridge system. Of the three configurations, the best is the bridge system, because in addition to using four diodes, the DC current produced will be more even.

2. Bridge Diode

Diode bridge is a diode consisting of four rectifier diodes combined into one diode which produces 4 pins, of which two are input and two are output. One of the advantages of this diode bridge is that the rectifier circuit becomes more concise because we do not need to arrange the four diodes into one, because the diode bridge is already one component.

Bridge Diode


Bridge Diode Symbol

Diode bridge has a function to rectify alternating current (AC) into direct current (DC) in one full wave. This type of diode also has four terminals, of which two are input voltage/alternating current (AC) and the other two terminals are output voltage (+) and output (-).

Bridge diodes generally have specifications for larger currents than ordinary junction diodes. However, the specifications of the diode bridge for small currents also actually exist depending on the type and series of the component.
The advantage of this type of diode is that it is easy to install in the circuit, because the four diodes have been strung together on the bride diode into one component.
Usually this diode is widely used for larger currents than normal diodes. However, there are also bridged diodes that are designed for certain small currents.

3. LED Diode (Light Emitting Diode)

LED diode or Lighting Emitting Diode is a diode that can emit light through both electrodes that are electrified, in this case an LED diode can light up when DC current is forwarded (forward bias). The LED type diode is one of the most popular types of diodes because it has many functions in electronic circuits related to lighting.

LED Diodes

LED Diode Symbol

Some of the uses of LED diodes in electronic equipment are LED TVs, new generation car and motorcycle lights, instrumentation equipment indicators, running LED displays and so on.
At this time, the use of LED diodes as lighting devices instead of ordinary lamps is increasing, because LED diodes can emit much brighter light with the same power than other types of lamps. Automatically the use of LED diodes can save electricity usage significantly.

Some of the uses of LED diodes in electronic equipment include:

• Electronic and electrical equipment indicator lights
• Home, road and vehicle lighting
• Running display (Running LED) and so on
This type of diode is capable of emitting many colors of light, such as red, orange, yellow, blue, green or white depending on the wavelength and the type of semiconductor compound used.

4. Zener Diode

Zener diode is one of the diodes that has an active role in stabilizing the voltage on the power supply or power supply. Unlike the installation of other diodes, in the design of electronic circuits that use this zener diode, it is installed in a reverse bias condition or a reverse bias condition.

The function and characteristics of the zener diode in the Forward Bias circuit are the same as the rectifier diodes in general, but the function and characteristics of the Zener diode in Reverse Bias are different from normal diodes.
Zener diodes can conduct electric current in Reverse Bias condition when the applied voltage exceeds the breakdown voltage.

Zener Diode and Symbol
The zener diode has a certain breakdown voltage according to its type and series. The most common unit of this type of zener diode is directly indicating the voltage in question. For example the 5V zener diode series for 5V voltage. However, there are also many series with certain unique codes according to the manufacturer and regional in each country of manufacture.

5. Photo Diode

Photo diode is a type of diode that has a function to convert light energy into electric current through its two electrodes. This type of diode is widely used as a light detecting sensor, such as:• On-camera light sensor

• Sensors count the number of vehicles
• Barcode scanner
• Etc.

The working principle of the photo diode include:

• If the photo diode is exposed to light, the resistance value in the diode will decrease, this causes an electric current to flow in the diode.
• However, if the photo diode does not get light or in the dark, then the resistance value in the diode will increase which makes electric current will be blocked or unable to flow.
In general, photo diodes are reverse biased in a circuit.

photo diode


photo diode symbol

6. Laser Diode

Laser light in electronic equipment is light produced by a diode. Almost the same as LED diodes that emit light, laser diodes are also one of the diodes that can emit light. It’s just that this diode emits laser light, which is a high-speed infrared spectrum radiation beam.

laser diode

laser diode symbol

LASER stands for Light Amplification by Stimulated Emission of Radiation. Laser diodes are widely used in scanners, blue-ray devices, and laser cutters. Devices that use laser diodes will usually be more expensive if the light intensity and laser power is greater. High-power lasers are widely used in light-based cutting devices that have been widely used in today’s technology.

7. Varactor Diode

The varactor diode is a unique type of diode. Because these diodes are made with semiconductors but can function like capacitors. The varactor diode has capacitive properties like a capacitor whose capacitance value can vary according to a given voltage control.
Varactor diodes are widely used in radio and television oscillator circuits. Usually a varactor diode is coupled with a capacitor and winding to generate frequency.
This diode is capable of operating in Reverse Bias condition. When the applied voltage is greater, the capacity value will decrease. The symbol for this type of diode is represented by a picture of a diode with a capacitor at the end.
Usually varactor diodes are widely used in several frequency-related electronic circuits such as oscillators, TV tuners and radio tuners.

varactor diode

varactor diode symbol

8. Schottky Diode

Schottky diodes have a lower forward or forward bias voltage than other types of diodes in general. Usually diodes have a forward voltage of 0.6 to 0.7 Volts, the average Schottky diode has a forward voltage ranging from 0.2 to 0.4 Volts. The main materials of Schottky diodes are chromium, platinum and tungsten.
Judging from the material, the Schottky diode consists of the main ingredients, namely chromium, platinum and tungsten. For its use, this diode is widely used in several high-speed switching circuits such as switching power supplies and high-frequency radio detector circuits
Schottky diodes are widely used in high-speed switching circuits such as switching power supplies and high-frequency radio detector circuits.

.Schottky Diode

Schottky Diode Symbol

9. SCR Diode (Silicon Controlled Rectifier)

SCR diodes actually consist of Schottky diodes that are designed in such a way as to produce SCR diodes that have 3 legs with certain characteristics. SCR diodes are widely used as high-speed automatic switch circuits, inverter circuits, TL lamp circuits, and others.

The shape of the SCR diode is physically similar to the transistor because it has 3 legs. But what makes the difference is the name of the foot and the function of the SCR itself. The SCR diode consists of anode, cathode and gate. Briefly, the workings of the SCR diode is that the current from the anode will flow to the cathode if the Gate leg is given a trigger.

Those are the types of diodes and the function of diodes in electronic circuits that are widely used according to the schemaku.com version. Actually there are many more types and types of diodes based on their derivatives for special purposes. But in general the most widely used is the type of diode described above
The three terminals of the SCR diode include the Gate terminal (G), the Anode terminal (A), and the Cathode terminal (K). The Gate terminal leg serves as a trigger to connect the Anode and Cathode.
So that the way the SCR diode works is that current can flow from the Anode terminal to the Cathode if it is triggered first by the Gate terminal.

It’s easier, that is, if the Gate terminal gets electricity, it will trigger an electric current from the Anode terminal to the Cathode terminal even though there is no electricity at the Gate terminal.
However, if to disconnect from the Anode to Cathode terminal, the voltage flowing from the Anode to the Cathode must be lowered to reach the holding current point on the SCR.

SCR diodes are often used as automatic switch circuits, high speed, inverter circuits, TL lamp circuits and so on.

SCR Diode

SCR Diode Symbol

10. Tunnel Diode

Tunnel diodes are high-speed diodes that are widely used in microwave or microwave circuits. Technically these diodes are made with semiconductors that are processed using a quantum mechanical effect called a tunnel.

Some circuits that use this diode are frequency detection circuits, converters, oscilloscope devices and others.

Tunnel Diode 

Tunnel Diode Symbol

11. Peltier Diode

Peltier diode is a type of diode that functions to convert electrical energy into hot or cold energy through its cross section. Currently, Peltier diodes are often used in several series of electronic equipment such as computer processor cooling devices, USB mini refrigerators and so on.

Peltier Diode

12. Crystal Diode

Krystal diode is the first time the discovery of a diode before various types of diodes appeared with its development. This type of diode is made from the contact between the semiconductor crystal and a certain point which results in the junction of P and N.

Diodes made of germanium are often used as radio receivers, detector diodes, or certain parts of circuits associated with high-frequency radio.

Crystal Diode

Crystal Diode Symbol