What Is a Diode? Why It Is Used in Embedded Circuits?
Tags: diode, embeddedcircuit, electricalproject
Published: 2023-02-11 21:55:16

Diodes are semiconductor devices used in many electronic circuits. They are used to direct and control the flow of current in electronic circuits. Many [digital integrated circuits](https://study.com/academy/lesson/digital-integrated-circuits-definition-types-examples.html) feature diodes to guard against potentially high voltage spikes. Germanium and selenium were used to create the earlier forms of semiconductor diodes, but more recent silicon designs have almost replaced them.

**What is a diode?**

A diode is a two-terminal electronic component that serves as a one-way conductor. It is made of a material that allows current to flow easily in one direction but resists the flow of current in the opposite direction. The most common type of diode is the semiconductor diode, made from silicon.

Diode works in:

Forward biased condition
Reverse biased condition 

In a forward-biased condition, the voltage across the diode allows a flow of current from the anode to the cathode. In a reverse-biased condition, however, the voltage applied across the diode is in the opposite direction compared to the normal flow of current and keeps any significant current flow from the diode.

It is worth noting that the voltage dropped across a current-conducting diode varies with the current passing through it, however, this variation is often minimal and only occurs over a wide range of currents.

Before we move further, have a look at the [1N4007](https://www.theengineeringprojects.com/2017/07/introduction-to-1n4007.html) which is a PN junction diode used for switching purposes in embedded applications. 

**Diode Symbol**

Diode comes with two terminals - anode (shown as a triangle in the symbol) and cathode (shown as a bar in the symbol). 

Anode is the positive terminal while the cathode represents the negative terminal. In some electrical circuits, the cathode is represented by the letter ‘k’ and the anode by the letter ‘a’. 

In the diode symbol, the arrow shows the direction of the current flow.

When the anode terminal is more positive than the cathode terminal, the diode will allow the current to pass while if the cathode is more positive than the anode terminal, then the diode will prevent the current from flowing. 

**Types of Diodes**

The following are the types of diodes:

Rectifier diodes: They are the crucial component of power supplies mainly used to convert AC current to DC current.

Zener diodes: They are used to regulate voltage and prevent the DC supplies from unwanted variations, making sure an accurate reference voltage is supplied to the main circuit.

Light emitting diodes (LEDs): They are used as indicators and for lighting.

[Photodiodes](https://www.electronicshub.org/photodiode-working-characteristics-applications/): They are employed to detect light. They can generate an electric current from light. The working principle of photodiodes is exactly opposite to LED diodes. The former converts light energy to electricity and the latter converts electricity to light energy. 

Varactor diodes: They are incorporated into electronic devices to tune radio frequencies. The internal capacitance of a varactor diode fluctuates in relation to the reverse voltage. It is a voltage-dependent semiconductor device and always operates in reverse bias situations.

**Why diodes are used in Embedded Circuits?**

Embedded circuits, also known as embedded systems, are electronic circuits that are used to control a specific function within a larger system. They are often used to control a particular aspect of a device or system, such as the display, audio, or communication capabilities. 

Embedded circuits are designed to be self-contained and are typically mounted on a printed circuit board (PCB) or integrated into the device or system in which they are used. They are found in a wide range of products, including automobiles, appliances, cell phones, and industrial equipment.

Diodes are used in embedded circuits for many reasons. One of the main functions of a diode is to allow current to flow in only one direction. This makes them useful for protecting circuits from damage caused by reverse currents. 

Diodes can also be used to rectify alternating current (AC) into direct current (DC), which is necessary for many electronic devices. In addition, diodes can be used as voltage regulators, to limit the voltage applied to a circuit to a specific level. 
They can also be used to create voltage drops in a circuit or to isolate one part of a circuit from another.

**Applications of Diodes:**

The main application of the diode is to keep the circuit from damage by preventing the current flow in opposite direction. However, the following are some more applications they can be employed for. 

1: Diodes are widely used to prevent the discharge of a solar panel battery when there's no sun available.

2: They can be used to regulate voltage by allowing current to flow in only one direction. This is crucial for applications where we want stable voltage, such as powering a microcontroller.

3: This semiconductor device can be used to convert AC to DC by only allowing current to flow in one direction, making it an ideal match for many power supply applications.

4: Diodes can be used to limit the amplitude of an incoming waveform, making it useful for audio processing applications.

5: They can be used to create a logical OR gate by combining two inputs and producing an output when either input is active.

6: They can be employed to electrically isolate two circuits, which is useful for preventing electrical noise from affecting sensitive circuits.