Electronic filters which filter a particular frequency and perhaps a specific range of different frequencies from the signal include active filters as well as passive filters. They are very different in terms of performance and design aside from their frequency filtering.
Let’s first talk about the fundamentals of passive and active filters before getting into the distinctions between them.
What Does a Filter Mean?
An electrical filter can be described is a circuit which may pass and amplify a specific band of frequencies while blocking or attenuating other frequencies. Also, they are employed to remove particular frequencies from the transmission.
During signal processing, filters are employed to remove noise from signals, extract the message from the signal, etc. There are various kinds of filters, including low-pass, bandpass, high-pass, analog and digital, passive and active, non-linear and linear, etc. The distinctions between passive and active filters will be covered.
Filters have a wide range of applications in the world of electronics. Here are some examples:
Radio communications
With filters, radio receivers will be able to “see” only the targeted signal whilst rejecting other signals in radio communications (Let’s assume that all other signals feature different frequency contents).
Direct Current power supplies
Here, the filters are utilized in removing noise (unwanted high frequencies) from the input lines of the AC. To lessen ripple, filters are also applied to the output of a power supply.
Audio Electronics
In the field of audio electronics, the crossover network refers to a system of filters utilized to distribute low-frequency audio into woofers, sounds of high-frequency into tweeters, as well as mid-range frequencies into midrange speakers.
Analog-to-digital conversion
To reduce aliasing, filters are inserted in the front of the ADC input.
What Does an Active Filter Mean?
Active filters are filters designed making use of active components like transistor and op-amp.
They are combined with capacitor and resistor, but excluding the inductor. These filters have the ability to increase power. However, in contrast to the passive filters, its design is more sophisticated.
Active filters need an external source of power to function because they utilize active components. The signal after filtering doesn’t need to be amplified. This gain could be altered by changing a particular parameter while the device is operating. The output and input impedances of an op-amp are low and very high respectively.
As a result, the active filter doesn’t face any loading effect issue at its load and source. Additionally, because its load is separate from its source, changing the load has no impact on how well the filter performs.
The need for the external source is the disadvantage of the active filter. The condition of this external source affects how well the filter works. Active filters’ active components have a finite bandwidth. As a result, they are inadequate for high-frequency signal filtering. Additionally, they are more vulnerable to harm from strong current.
The circuit’s op-amp is typically utilized in a specific integrated fashion. So make sure it’s compact and lightweight. Op-amps are known to have a low output and high input impedances. Therefore, its loading effect present at load and source is eliminated by these active filters.
However, active components have limited bandwidth, which occasionally results in problems in operating high-frequency signals. Additionally, this active filtering mechanism requires a dc source because it is unable to draw its driving power out from the input signal.
What are the Characteristics of an Active Filter?
- Op-amps and transistors are examples of active components used in active filters.
- Also, it includes passive parts like capacitors and resistors but not inductors.
- In order to function, it needs external source of power.
- Its output impedance is very low and its input impedance is extremely high.
- The filter can be readily cascaded to enhance the filter’s order without having to worry about the amount of the loss.
- At the output, it offers a substantial power gain.
- Its electrical properties are unaffected by changes in load resistance.
- It features sophisticated circuitry.
- Its design is compact, and its size is small
- Due to the active components’ limited bandwidth, its frequency range is limited
- It is more expensive than the passive filters
- High frequency operation is not possible.
- It is unable to tolerate strong currents.
What are the Applications of the Active Filters?
- In communication, active filters play a huge role in cutting through noise, so as to help in isolating signals from different channels, and enhance the distinct message signal coming from the emphasized signal.
- The designers of instrumentation systems use these filters to identify the necessary frequency apparatus as well as separate unwanted ones.
- Before converting analog signals into digital signals, active filters may be employed to reduce the bandwidth of the analog signal.
- Audio systems have active filters to convey different frequencies to different speakers. Applications for recording and playing back music, for instance, are necessary in music to help in controlling its frequency components.
- These filters connect psychological sensors to diagnostic tools and data logging in biomedical devices.
Benefits of the Active Filters
The following are a few benefits of the active filter
- No resonance problem
- They have the ability to completely eliminate harmonics,
- It helps to regulate voltage,
- Active filters compensate for reactive power,
- They operate consistently.
Pitfalls of the Active Filters
- They are costly
- The control systems they offer are complex
What Does a Passive Filter Mean?
Only passive parts, such as resistors, inductors, and capacitors, are used in passive filters. It’s relatively affordable and features a simple design. Also, they don’t give any electricity because this filter operates without an external source of power. They do, however, employ an inductor to enable them to handle high current.
Extremely high frequency can be handled by passive components. Passive filters therefore are employed in high-frequency applications. However, extremely low-frequency applications are not appropriate for them. In order to increase the inductance value, a larger, bulkier inductor is needed, which also increases the filter’s size and price.
The filter’s overall resistance is directly impacted by its load resistance. As a result, any modification to this load resistor will alter the filter’s electrical properties. It features a constrained output and input impedance, and loading has an impact on how well they work.
Its output signal features lower magnitude in contrast to its input signal because passive components draw power from its input signal, hence the passive filter somehow doesn’t generate power gain. It needs post-filtering amplification.
Passive filters have good response for the radio frequency band. However, in the low-frequency applications, the circuit’s use of an inductor leads to issues. Similar to the case with low frequencies, its inductor’s inductance should be increased, which necessitates adding more turns to the coil.
Passive filters’ input and output impedances become problematic below the Radiofrequency range. Therefore, low-frequency operations are not well suited for these. In essence, the categorization of filters is produced by the frequency band that is permitted and prohibited.
Characteristics of the Passive Filter
- Passive filters don’t need an external source of power because they exclusively use passive parts like resistors, capacitors, and inductors.
- There is no power gain
- The features of a passive filter are impacted by changes in the load resistance.
- Because it consists of an inductor, it is free of frequency restrictions and is typically utilized for many high-frequency applications.
- Because a huge inductor is needed for its the low-frequency applications, its passive filter grows in size and becomes more expensive.
- The design is straightforward and easy.
- It has a greater size and is heavier due to larger inductors;
- It is less expensive than the active filter.
Benefits of the Passive Filter
- Stability is guaranteed
- There is no need for power supply
- It is less expensive
- Designing it is easy
- It has a high frequency
Cons of the Passive Filters
- Their size is large
- At times, they could have response problems
- The gain is usually 1 or lesser
- When utilized with the inductors, it is usually bulky
What are the Applications of the Passive Filters?
Passive filters have many applications. These include:
- They could be utilized in band pass filters to reject signals at any and all frequencies below and above this band.
- Also, they can be employed in the high pass filters, particularly in audio amplifiers.
- They function as I.F. transformers seen in earlier TV and Radio equipment to pass the band of different radio frequencies through one step of an intermediate frequency amplifier.
- Furthermore, they are employed for band stop filters TV and older radio receivers.
Active Filter vs Passive Filter: What are the Major Differences?
The primary distinction between the active filter vs passive filter is that the active components, such as op-amps and transistors, are used by active filters in filtering the electronic signals. In contrast, the passive filter creates a signal for a certain band using passive parts such as an inductor, a resistor, as well as a capacitor.
Another significant difference between these two is whether the active filter requires an external power source to function. While passive filters don’t require an external source.
We are aware that filters are circuits with the capacity to pass through a specific frequency range while rejecting frequencies outside of the band. In essence, filter circuits display the frequency selectivity property. We’ll go over some more variations between active filter vs passive filter.
Due to the existence of the active components, these active filters are costly. On the contrary hand, because they contain passive components, the passive filter is sufficiently affordable. Active filters have a complicated circuit orientation. While the circuit for relatively passive filters are simpler.
In contrast to the passive filters, active filters feature a higher quality factor value and require an external power source to operate. Nevertheless, because they draw the energy necessary for effective operation from its supplied input signal, passive filters don’t really require external sources of energy.
Passive filters are ideal for RF range operating because the inductor, the main component used in them, produces barriers at very low frequencies. Active filters, on the other hand, provide a stronger response for low frequencies.
Passive filters have relatively high weights, compared to active filters’ low weights. Active filters are more sensitive to temperature variations. Passive filters, in contrast, are less susceptible to temperature variations.
Comparison Active Filter vs Passive Filter
Power Source
- The Active filters need an outside power supply to function.
- Passive filters don’t need an outside power source in order to work.
Gain
- The active filters increase output signal as well as offer a significant power gain.
- A passive filter offers no power benefit. In actuality, this output signal is weaker than its own input signal in magnitude.
Design
- The design of the active filter is complex in nature
- The design of the passive filter is simple in nature
Loading Effect
- Because active filters have high input and low output impedances, loading effect is not a concern.
- Passive filter does have a problem with the loading effect.
Bandwidth
- Due to the frequency restrictions of the active components and their constrained bandwidth, active filters are unable to filter signals of high-frequency
- There are no frequency restrictions for passive filters.
Size
- Passive filter is heavier due to the size of the inductors and are bulkier, especially at low frequencies when big inductors are required.
- The Active filter is compact and possesses a small weight and size.
Cost
- Passive filters are manufactured from inexpensive passive components,
- Active filters require expensive active components as well as a power source.
Conclusion: Active Filter vs Passive Filter
Therefore, it may be inferred that each type of filter has a specific operating range. However, in the fields of signal processing and communication, the active filter is utilized more frequently than the passive filters.
