How Does the Diode Direction Impact Current Flow in a Circuit?

The flow or direction at which current passes in a circuit is important because it underscores whether the circuit would use the right current or not. The diode is responsible for this and therefore, choosing the right diode direction is important.

When designing a circuit, you want to factor in which ends of the diode should be positioned where and some of the reasons are covered in this article.

What is a Diode?

Let us start by understand what the underlying concept, diode, means. It is one of the semiconductor devices used in designing a Printed Circuit Board (PCB). The primary function of the diode is to enable the flow of current in one direction. This explains why it is also called diode one way.

Understanding the Diode Current Flow Direction

When we say that the electrical current is meant to go through one pathway, it sounds confusing. Does it mean that in a circuit, it is not possible to have the current move both ways?

A better explanation would be to understand the current flow direction of the diode. Here are some of the things you need to know.

The Terminals

A diode has two terminals, which are the cathode and the anode. These terminals also serve as the medium for regulating current flow.

Here is a summary of what they are meant to do:

  • Cathode: the cathode is the negative terminal in the diode.
  • Anode: on the other hand, the positive terminal is called the anode.


For current to flow through the diode, the matching voltage must be applied. For example, a negative voltage should be applied to the cathode and a positive voltage applied to the anode.

The outcome of doing this is that the current will start flowing through the diode.

Reversed Diode Flow Direction

While the above is the standard, you may want to reverse the process to see what happens. You will find out that electrical current wouldn’t flow when a positive voltage is applied to the cathode and the negative voltage applied to the anode.

This is because the diode doesn’t support such reversal, which tends to promote the flow of electric current in the opposite direction.

Therefore, the flow of current in the diode is towards the one direction and blocking off a similar flow in the other direction. A bulk of the current flow and regulation is enabled by the built-in electric field in the diode.

Diode Polarity Marking: What You Need to Know

There are two ways to determine the flow of electric current in a circuit. These are the polarized and the non-polarized components.

Polarized Component

This refers to the electronic component that has been polarized – this refers to the connection of the circuit in one direction. In this case of the diode, electric current is meant to flow from the positive terminal (anode) to the cathode – the negative terminal.

Non-Polarized Component

When an electronic component is made up of non-polarized marking, it simply means that electric current can flow from any direction. This is possible because the component can be connected to any direction and still retain the basic functions.

How to Identify Diode Direction Marking

While the flow of current in a diode is from the anode to the cathode; there is a possibility that you may mix it all up.

Therefore, we think that highlighting some of the things to look out for will make the task easier for you. Here is how to excellently determine the diode PCB marking:

  • Check the Marking: it is possible for the diode to have the marking, which makes the current flow identification simpler. In this case, you tend to find the diode symbols (+ and -) denoting the anode (positive) and the cathode (negative).
  • Arrow Direction: however, there is also the possibility that the diode wiring direction, as mentioned above, is not present. In this case, the rule of thumb is to follow the direction of the arrow.

The Types of Diodes and the Functions in a Circuit

Diodes are one of the polarized electronic components used when making a Printed Circuit Board (PCB). There are several types of these polarized components, including the diodes, Integrated Circuits (ICs), tantanium capacitors, and transistors.

However, when it comes to the diodes, there are several options to choose from. Examples of the diodes you can use and their functions in the circuit include:

1. Light Emitting Diodes (LEDs)

These are one of the popular diodes and they are mostly used with the lighting-related products.

With a higher reverse resistance and the ability to produce light when a forward current flows through it; the LED aids the conversion of electric current into an optical signal.

2. Switching Diodes

These types of diodes are used in the AC-to-DC converters, as well as electric motors. The functions include:

  • Aiding the interruption of electric current, without exposing the device to damage.
  • The switching diodes also enable electric current switching between two points.

3. Zener Diodes

These are the diodes that regulate the voltage in a circuit. The most regulatory mechanism is to act as a short circuit for regulating the voltage when it goes above the forward voltage drop.

4. Silicon Diodes

Despite the fact that the silicon diodes do not thrive at instantaneous conduction of electric current from one point to another; they help in the following ways:

  • Silicon diodes are responsible for facilitating frequency conversions in a radio circuit.
  • These diodes also convert the Alternating Current (AC) to Direct Current (DC).
  • They also flow at an actual current rate for a short time.

5. Germanium Diodes

These are the diodes used to regulate the presence of higher voltages. The following are some of the attributes of the Germanium Diodes:

  • They aid in the detection of waveforms, such as the oscillator’s voltage and the radio signals.
  • Germanium diodes act as the rectifiers in the high-voltage applications.
  • As a way of indicating higher voltages, these diodes tend to emit light anytime the forward current passes through.

The list of diode types also includes:

  • Photodiode
  • Junction diode
  • Varactor diode
  • Tunnel diode
  • Triac
  • Schottky diode and;
  • Diac

Diode Connection Processes in a PCB

There are two (2) major ways by which a diode can be connected to the Printed Circuit Board (PCB). These are based on the Through-Hole Technology (THT) and Surface-Mount Technology (SMT).

For the THT process, it has to do with the insertion of the diode’s pins through the holes that have been drilled on the circuit board.

Integrating a diode into the PCB via the SMT process requires soldering. For the best results, the following considerations should be made:

  • The right soldering temperature should be used.
  • You should also consider using the right amount of solder for the process.

Resistance Test vs. Diode Test – Two Testing Methods for Diodes

As one of the most important semiconductors and electronic components in a PCB, the diode needs to be subjected to some tests. The diode test mode and the resistance test mode are the two best ways to go about it.

The resistance test mode is favored for the following reasons:

  • It involves the use of a multimeter to measure the diode’s current-carrying capability.
  • Voltage drop due to forward-bias is easier to determine.

Diode Test Mode

The following processes go into the use of diode test mode to check the diode’s performance:

  • Turn off the circuit’s power supplies.
  • There should be zero voltage on the diode.
  • The multimeter can now be fixed. It aids the measurement of the DC or AC’s voltage, as per the requirements or specifications for the circuit.
  • You can now turn the dial to Diode Test Mode.
  • Connect the diode to the leads for the test and take a recording of the measurement.
  • Reverse the leads and take the measurement.

Resistance Test Mode

For the resistance test mode, the following steps should be taken:

  • Turn off all the power supplies coming into the circuit.
  • Make sure that the diode doesn’t have any voltage.
  • Fix the multimeter and adjust per the requirement for the DC and AC’s voltage.
  • Turn the dial of the multimeter to Resistance Test Mode.
  • Remove the diode from the circuit and connect it with the test leads.
  • Note down the measurement displayed.
  • Reverse the test leads and take the new measurement.

Of What Benefit is the Diode’s Direction?

When the electric current from the positive terminal (anode) to the negative terminal (cathode), it simplified the process of extending the current to the other parts of the circuit. Thus, an accurate connection is required and this is one of the benefits of using a diode.

The other known benefits of using a diode’s accurate direction include:

  • Waveform detection, especially the radio signals.
  • Conversion of electric current from one to the other. For example, you can use a diode to convert an Alternating Current (AC) to Direct Current (DC), especially if you are using a rectifier circuit.
  • Diodes also control voltage’s frequency in circuits.

Hillman Curtis helps to place the diodes in the right direction in your circuit. We also make the diode polarity marking so it is easier to use it accurately. The diodes we produce for you can be applied to the following application areas: In Varactor circuit (signals demodulation), In Switching Current (current steering), and In Regulator Circuit (over-voltage protections).

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