Cathode vs. Anode Diode: How to Indicate Placement Orientation of Diodes on Your PCB

Diodes are a common part of consumer electronics. These have made our lives easier and today our most of the routine activities include diodes. These are simple components of electronics. The role of a diode is to allow the flow of current only in one path and it stops the current flowing other paths in the devices. The impedance has no influence on the current that a diode controls. There is a lot more to diodes in the field of PCB. We are going to highlight some important aspects of diodes in our discussion so let’s get started without any delay!

The Diode

As you already know the current that flows through a diode cannot flow in more than one direction. Now this condition is a forward bias condition. For making it more simpler, you can consider diodes as some kind of electronic valves which regulate the current flow so that the device can keep working normally. In case a diode is experiencing a negative voltage, there will be no current flowing which will make your diode an open circuit. Besides a forward bias condition, there is also a reverse bias diode condition. Basically, biasing means that the diode is determining different amounts of voltage and current at different spots in a circuit. The diodes include semiconductors as fundamental units in their structure. The semiconductor diode has two sides called P-type and N-type. In the center, there is a P-N junction. There are also some leads connected to these diodes which make the assembling of these diodes in consumer electronics much easier. 

Diode Functionality

In order to understand the diodes fully, we need to learn about their functionality. As we already know that diodes have leads and two of them connect with the sides of the diodes. The lead which joins with the N-type is called a cathode while the P-type lead is the anode. The cathode is a negative side while the anode is a positive side. Now, keep in mind that all the functioning of the diode revolves around this region in which the P-N junction is also included. We are going to take a look at the reverse and forward bias condition of a diode in detail below:

1. Forwards Bias Condition: In case the voltage connects with the positive anode and its negative side joins with the cathode, it will make this diode a conductor and the forward bias condition will establish which means the current is flowing.
2. Reverse Bias Condition: In this case, if we reverse the voltage sides, meaning connecting the negative side of the voltage to the anode and the positive side to the cathode, it will establish the reverse bias condition. The current does not flow in this condition. The diode becomes an insulator.

The Two Regions of a Diode

The two most important regions of a diode are its N-type and P-type regions. These regions will help you understand the working of a diode on a much deeper level. In a general diode, the cathode is always on the right side while the left side represents the anode. At the anode, the current flows from positive to negative. You can also consider a large minus sign on the cathode which shows this side of the diode is negative if you are working with a diode in a forward bias condition. 

Diode Characteristics

It’s time that we consider some salient characteristics of the diode in this section:

• The reverse voltage of a diode means the total amount of voltage that it can allow before it undergoes complete failure and the direction of the current, in this case, is always reverse.
• The reverse voltage of the diode also goes by peak reverse voltage or peak inverse voltage so you can learn one of the names at your convenience. 
• There is a fixed limit of reverse voltage for every diode and increasing this limit is not recommendable at all. 
• The maximum current rating of a diode means the total amount of peak current which flows through the diode. Just like we cannot change the reverse voltage, the peak current rating also remains constant as it causes adverse damage to the diode we are working with.
• The diode is a versatile component for electronics means it can act as an insulator and a conductor. 
• It has critical applications in different industries as well due to its remarkable features, efficient performance, and simplified nature. 

Anode vs. Cathode Diode

All the LEDs that you have seen or used by far contain two diodes which are cathode and anode. Without these diodes, no LED can perform efficiently. To fully learn about the LEDs, we need to understand how LED polarity works in detail. Basically, the LED polarity means the route that the current takes for following. The LEDs contain diodes and due to the presence of diodes, the current in them can only follow a single path to flow. Now, let’s shed light on the anode and cathode individually in the next sections for easy understanding.  

What is an Anode?

An anode in a LED is actually a diode and is positive. An anode of LED acts as a terminal which is a door that allows current for flowing. 

What is a Cathode?

If you have understood the anode, learning about the cathode is a no-brainer. It is just contrary to the anode. Just like an anode that will allow the current to flow, a cathode in the LED will not allow it to flow and will make the current leave its route. 

How to Tell Anode vs. Cathode

Their signs will let you know! Follow the anode’s positive sign and the negative sign of the diode to differentiate between the two easily. If their signs are too small, you can use a magnifying glass for proper visualization. There are some other differences between an anode and a cathode that might be helpful for you in your upcoming diode projects. So let’s get started!

The Differentiations Based on the Electrical Charge

Now you are about to learn the trick to determine the anode and cathode easily. Since these both are involved in the current flow, sometimes it becomes tricky to determine the two. The anode always captures the negative changes because it is positive. The positive charge on the anode makes it an electron receptor. Therefore oxidation takes place at the anode. The cathode is the proton receptor because it has a negative charge and attracts protons. The purpose of a cathode is to generate the electrons. Once the negative charge has been established, it will make the current follow the anode from the cathode. 

Anode vs. Cathode Diodes: The Major Differences

After this section, you will be able to easily differentiate between anode and cathode. The differences between anode and cathode include:

1. Type of Terminal

One easy way to determine the anode and cathode is that the anode is the positive terminal while the cathode is the negative terminal. 

2. Type of Charge

The anode gives away the electrons which means it undergoes oxidation while the cathode receives the charge which means reduction making it a negative terminal, unlike the anode. 

3. Electric Current Flow

The anode allows the current to enter the LED while the cathode makes the current go out of the LED. 

4. Positivity and Negativity

You can also determine the anode and cathode as per their charges. It is one of the simplest methods to determine these two terminals. The anode is always positive while the cathode is negative. 

5. Oxidation vs. Reduction

At the anode, oxidation takes place while reduction takes place at the cathode. It is also a good way to differentiate between the two. 

6. The Pin’s Length

Sometimes, you can also determine both from the size of the pins which are different for both terminals. However, this is not always true since manual cutting and human errors can sometimes make them alike and it gets difficult to differentiate between anode and cathode. Don’t worry, you can still determine the cathode in this regard. So it means if you get successful in finding the cathode, you can determine the anode ultimately. There are tips that will help you find the cathode in the first place:

• If the casing if flat and joins with the diode then it is a cathode
• If the casing is protruding a little bit then it is a cathode

Advantages of DIodes: 

• Diodes ensure less short circuits
• These are reliable for the regulation of voltage and current
• A diode prevents overvoltage
• Diodes dont let overcurrent damage the electronics
• These are for easy conversion of AC to DC
• Diodes are reliable for giving DC to electronics

Disadvantages of Diodes:

• A semiconductor diode has its limitations for working with the extreme reverse voltage
• Diodes are not much responsive
• These have reverse saturation current which is not beneficial 
• Diodes produce a higher amount of noise in some devices

Diode Orientation and Placement

Diodes are simple components. But when we talk about their polarity, they become a challenging concept. There are different types of diodes including plug-in diodes and patch diodes because their orientation and assemblies are different. The two common types of diode assemblies include DIP and SMT. Therefore it is important to determine which type of assembly you are going to use as per your diode type. If you are hiring a diode assembly firm, then you have to be careful with the diode orientation because there is no margin of negligence as it can cause diode failure. The silkscreen of PCBs is helpful so that you can have the complete diode orientation information. There are different devices that use bidirectional diodes. Proper ground planing is important to maintain their efficiency. It will also prevent the stub diodes from production and ruin the performance of consumer electronics as well. 

Don’t Forget the Functional Implications of Component Orientation

There are some tips that you need to follow when you are assembling PCBs to avoid complications on all counts. It is important to consider these because the functional implications matter when we are working with PCBs. Take a look at them below: 

• Human interface considerations: Opt for human interfacing for the PCB parts. You can rely on locked and unlocked connectors for this purpose. It is also important to position the switches and wiring so that it will improve the PCB’s efficiency. Proper orientation of PCB parts is crucial so that you can easily proceed with the PCBs. Also, try to maintain a decent distance between the PCB parts so that you can avoid mishaps as much as possible and protect your PCBs from possible damage. 
• Marking orientation: You need to make sure that your silkscreen is giving accurate statistics so that it will allow you to prevent any possible complications. The polarity indicators should be involving accurate pins for this purpose. These measures will make your marking orientation feasible. 
• Quality validation: It is important to pay close attention to the components that are present in the form of groups or are alike in nature. If you will do this, you can greatly lower the risk of PCB reworking and assembling PCBs from scratch. Quality validation is highly crucial so that you can produce highly efficient and industrial-grade PCBs with the least hustle. 
• Thermal performance: Thermal performance of PCB parts also matters and is different for each component. Some components are critical and sensitive and need proper orientation to allow ventilation so that they dont get damaged due to overheating. 

Summary

Diodes are highly important for the fine performance of several devices. Due to this reason, diodes need our special attention and special handling to drive positive results from them. From aerospace to defense, diodes have major applications in different domains around us. We have highlighted some major aspects of diodes in this post so that you will be able to easily understand them.

Also, you are now able to differentiate between anode and cathode easily since we have discussed some useful tips and tricks for that. We hope that diodes are now a no-brainer for you and can develop stunning diode projects in the future as well. We will catch you in the next one with something more fascinating from physics!