What does an Electric Filter do? (Full explanation with FAQs)

Electric filters clean electrical signals of unwanted frequencies in the audio and intermediate ranges. RF and microwave filters have the same function but in the radio and microwave frequency range. 

Do you want to know more about what an electric filter does? If yes, then you are in the right place.

This article will expose you to everything an electric filter does. We will help you understand the working principle of an electric filter.

Let’s start. 

What Is a Filter?

A filter is a circuit that can pass through (or enhance) certain frequencies while attenuating others. Hence, a filter can remove essential frequencies from signals that also include unwanted or unrelated frequencies.

Filters have a wide range of useful uses in the world of electrics. Examples include:

  • Radio communications

 Radio receivers can only “see” the required signal due to filters because they reject all other signals (assuming that the other signals have different frequency content).

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  • DC power supplies

We can use a filter to remove unwanted high frequencies (also known as noise) on AC input lines.

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  • Audio electrics 

A crossover network is a filter group that directs low-, mid-, and high-frequency sound waves to woofers, midrange speakers, and tweeters.

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  • Analog-to-digital conversion

We can place filters in front of an ADC input to minimize aliasing.

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Types of Filters

Below is the list of common types of filters.

#1. Air Filters

Air filters can be whole systems or replaceable elements; they are components or systems that filter the air through filtering elements. The intended application, physical size, filter type, filter medium, and airflow rate are important characteristics. We utilize air filters when a system needs air free of particles. Before the air is exhausted, they are also used to clean it. Typically, an air filter system comprises a filter element and the housing that they house it in. They are shaped for certain uses like furnaces, range hoods, clean rooms, and car engines. An air filter can eliminate many contaminants, such as dust, gases, oils, and bacteria.

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#2. Electric Filters

Electric filters mostly enhance or remove undesirable frequency components from electric signals. They often work at frequencies lower than RF (radio frequency). Both AF (audio frequency) and IF (intermediate frequency), which are power frequencies, fall within the typical operating frequency ranges. Electric filters come in various forms and serve various purposes, including passive or active, analog or digital, low pass, and high pass. We can also use electricity filters to reduce or eliminate electrical noise.

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#3. EMI/RFI Filters

Electrical devices called EMI/RFI filters reduce or eliminate EMI (electromagnetic interference) or RFI (radio frequency interference) in a system. The intended application, filter type, and electrical parameters such as voltage, current, frequency ratings, and bandwidth are important specifications. Electric and telecommunication applications utilize EMI/RFI filters primarily to reduce or eliminate EMI or RFI signals that interfere with the performance of an electrical system or product. Typically, the filter is put in between an AC power line and the equipment that needs to be protected. Versions can also be used as stand-alone components for placement in utility cabinets, included in connectors, or inserted on PCBs. The filters are also capable of disposing of EMI/RFI emissions coming from the machinery.

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#4. Fluid Filters

Fluid filters are devices or systems that purge fluids of undesirable particles as the fluids flow through the filtering elements. They could consist of whole systems or only the individual replaceable parts. The most important characteristics are the intended use, filter type, filter material, filtrate and filtrand, particulate size, and flow rate.

Fluid filters are typically employed in systems where the fluid must be free of particles or debris to protect or clean the equipment before it is released into the environment. Typically, a filter element and housing make up a fluid filter system. They come in shapes tailored to certain uses, such as metalworking fluid filters, cooling system filters, and engine oil filters. Many materials, such as fabric, foam, carbon, and sintered metals like stainless steel, can create the filter media.

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#5. Fuel Filters

Fuel filters, which can be a full system or a replacement part, filter out undesired components from a gasoline system as the fuel runs through them. The intended application, filtrate, particulate size, flow rate, and physical dimensions are among the most important criteria. We can use fuel filters to remove impurities or undesired materials from gasoline to protect machinery and improve fuel efficiency. The filters come in various forms and sizes depending on the desired application. They typically build them for a specific application, such as a diesel or aircraft engine, filling tanks, etc.

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#6. Hydraulic Filters

Hydraulic filters are devices or systems that clean hydraulic fluids of impurities. They might be full systems or just replaceable parts. Hydraulic filters are typically used to remove undesirable particles or pollutants from fluids used in hydraulic cylinders or other hydraulic fluid-using systems. The filters may require various materials or types depending on their intended use. Often, components filter out particles.

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#7. Optical Filters

Optical filters are devices placed in the pathways of light sources to permit or transmit only particular wavelengths. The intended use, material, wavelength characteristics, and physical dimensions are important parameters. Optical filters are most frequently utilized in photographic applications, although they can also be used in other scientific or technical activities. There are many different kinds of optical filters, such as UV, infrared, and bandpass filters, each serving a particular purpose and enabling the transmission of a particular wavelength or range of wavelengths. Some are only relevant for photography. Thus they might not apply to technical tasks.

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#8. RF and Microwave Filters

Microwave and RF Electrical filters can either pass or block a particular frequency. The intended application, filter type, and frequency characteristics are important specifications. The main purpose of RF and microwave filters is to enhance or remove undesirable frequency components from electric signals. However, they typically operate at microwave frequencies and radio frequency ranges (megahertz and gigahertz). Various filters are available, including low pass, high pass, band pass, and reject pass. Each has a certain wavelength or range of either blocked or transmitted.

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#9. Water Filters

Water filters are equipment or systems that remove impurities from water; they can be full systems or replaceable parts. The intended application, flow rate, particle size, and physical dimensions are important criteria. Water filters are typically utilized in systems that need to filter or clean the water to eliminate dirt and particles. Water filters are used in various applications, such as water parks, refrigerators, aquariums, and wastewater treatment plants. Depending on the application, several sizes and types of filters are available.

Types of Electric Filter

The electric filter is classified into two, which include: 

#1. Active Filter:

Active filters are constructed using active components such as diodes, transistors, and opamps. The various types of active filters include: 

  • Active Low Pass Filter
  •  Active High Pass Filter
  •  Active Band Pass Filter
  •  Active Band Reject Filter

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#2. Passive Filter

“passive filter” refers to a filter circuit comprising passive components such as resistors, capacitors, and inductors. The various kinds of Passive Filter include: 

  • Passive Low Pass Filter
  •  Passive High Pass Filter
  •  Passive Band Pass Filter
  •  Passive Band Reject Filter

Therefore from the above concept, we can say there are four types of Electric Filters which are,

Low Pass Filter

The Low Pass Filter is a filter circuit that enables low-frequency signals (from 0 to a predetermined cut-off frequency) to pass through while rejecting signals with frequencies above that cut-off frequency.

For instance, a signal at 50 MHz is present, but we require a signal up to 25 MHz. In this instance, a low pass filter was required to permit the passage of signals with frequencies between zero (zero) and 25 MHz while rejecting signals with frequencies higher than 25 MHz.

Examples of Low Pass Filter include: 

RC Low Pass Filter: This filter circuit was created using resistors and capacitors.

RL Low Pass Filter: This filter circuit was created using an inductor and a resistor.

RLC Low Pass Filter: This filter circuit was created using a resistor, capacitor, and inductor.

There are several applications of Low Pass Filter, they include: 

  • A low Pass Filter is used in Digital Signal Processing
  •  It is utilized for audio equalization.
  •  It is applied to audio to lower high-frequency noise.
  •  Converting analog signals to digital ones serves as an anti-aliasing filter.

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High Pass Filter

High Pass Filter refers to the filter circuit that enables the passage of high-frequency signals beginning at a predetermined cut-off frequency while rejecting signals with frequencies below that. Examples of High Pass Filter include: 

  • RC High Pass Filter
  •  RL High Pass Filter
  •  RLC High Pass Filter

There are several applications of the High Pass Filter, they include;

  • A high pass filter is used in digital image processing.
  •  It used to reduce low-frequency noise 
  •  It is also used as the treble booster circuit in the audio system.

Band Pass Filter

Band Pass Filters permit the passage of signals with frequencies that fall within a given band while rejecting signals with frequencies that fall outside that band.

Although we have 60 MHz signals, we also require 20 to 30 MHz signals. So, we required a bandpass filter to pass signals between 20 and 30 MHz while rejecting signals below 20 and above 30 MHz.

Examples of Band Pass Filter include:

  • RC Band Pass Filter
  •  RL Band Pass Filter
  •  RLC Band Pass Filter

Applications of band Pass Filters include:

  • Band Pass filters are used in the phone system.
  •  The SONAR system employs it.
  •  It is applied in audio technology.

Band Reject Filter

The term “Band Reject Filter” refers to the filter circuit rejecting signals with frequencies that fall within a specific band while allowing the passage of signals with frequencies that fall outside that band.

Although we have signals of 100MHz, we also require 0-30MHz and 60-100MHz. So, a band reject filter is necessary, allowing communications with frequencies outside the 31-59MHz band while rejecting transmissions with those frequencies.

Example of Band Reject Filter includes:

  • RLC Band Reject Filter

A Band Reject filter can be created using an RLC parallel circuit. The circuit functions as a band-reject filter circuit in parallel resonance conditions. You can obtain the output by crossing the resistor.

Applications of Band Reject Filters include:

Band Reject Filters are used in telecommunications systems.

General Applications and considerations of filters 

Filters that process fluids like air, fuel, water, hydraulic oil, etc., typically rely on paper, foam, or other similar materials whose pore sizes can be adjusted to pass only things below particular sizes. There are numerous and diverse designs, such as baffled, pleated, spirally coiled, and finned. The elements of filters can be purchased separately or in entire assemblies with housings. Filters are frequently changed. Filters frequently focus on a single application. Also, household water filters commonly represent the housing/cartridge design. Some filtration systems, such as sand filters used in water filtration that are frequently backflushed to recover capacity, are made to be cleaned.

While considering fluid filters, flow rate and pressure drop are crucial factors because any filtering component in a flowing stream will lower the pressure of an incoming stream. Flow rate and pressure will decrease the more restrictive the filter is.

HVAC systems, spray booths, compressors, engines, electric enclosures, cleanrooms, etc., employ air filters to remove particles, dust, smells, germs, and other impurities from incoming air. When process air needs to be cleaned before being released back into the environment, they are employed on the discharge side of numerous industrial processes.

In order to purify water before it is used for drinking, bathing, and other purposes, waterworks, swimming pools, homes, campers, etc., all utilize water filters. They also clean boiler feed water, cooling water, and other industrial processes.

Filters that operate in the electromagnetic spectrum include electric, EMI/RFI, RF, and microwave filters. They are utilized in industrial and military contexts to eliminate undesirable signals, electrical noise, etc. Data acquisition systems, variable frequency motors, etc., are a few examples of uses.

Important Attributes of filters

The important attributes of filters include the following:

#1. Maximum Flowrate

The flow rate for air filters is typically expressed in cubic feet per minute (cfm) and gallons per minute (gpm) for liquid filters.

#2. Intended Application

Finding the right filters is easier by choosing the filter application rather than selecting whether you require a gasoline filter, fluid filter, etc. However, selecting diesel and gas engine filters may result in air, gasoline, and fluid filters being returned when you want an automobile oil filter.

#3. Filtrate

“filtrate” refers to the media that passes through the filter. Collecting oil from this location will yield hydraulic and car engine filters.

#4. Filtrand

The term filtrand describes the material that the filter removes from the filtrate. Water filters and similar items will result from picking up oil here. We can also create similar filters by checking oil and paint as the filtrate, which may be handy for spray painting.

#5. Filter Type

By selecting one of the element-only options, you can get replacement filters for your current housings for air and other fluid-handling filters. The type of filter used for electric, EMI/RFI, RF, and microwave signals can indicate which signals are passed through (low pass, for example) as well as certain filter types like Butterworth, for example. Optical filters come in various similar sorts that we can choose from.

#6. Filter Media

The term “filter media” refers not to the raw material itself but to the filter’s filtering medium. In other words, if you wanted to buy activated carbon in bulk, you would look under the media, such as carbon, sand, perlite, diatomaceous earth, etc. If you were looking for an activated carbon filter cartridge, you would find it here.


What does an electrical filter do?

Electronic filters can either increase desired frequency components or remove undesirable ones from the applied signal. They can be either active or passive. Digital or analog.

What are the top three filters in use today?

The three most popular varieties are reverse osmosis, ultrafiltration, and microfiltration membrane filtration processes.

What are the benefits of using a power filter?

They are incredibly user-friendly and offer superior mechanical, chemical, and biological filtration. They are also made to hang off the back of your aquarium and are the ideal filter for most common aquarium sizes hosting a variety of tropical species.

How can you tell whether a filter is stable?

The fundamental filter transfer function’s poles must all fall inside the unit circle in the z-plane for a digital filter to be considered stable. Every pole outside the unit circle contributes an impulse response component that grows exponentially, making the filter unstable.


Filters are critical in many common applications, including power supplies, audio electrics, as well as radio communications.

If you carefully read through this article, you will realize that it provided you with the necessary information you need to know about an electric filter. We have also exposed to you what an electric filter does.



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