Last Updated on October 22, 2023 by Kevin Chen
When you see the word ‘filter’, the first thing that should come into your mind is elimination.
You will probably assume that something should be removed from the rest.
In the field of electronics and communication, a device may receive or transmit loads of signals.
Not all the signals are desired to be used.
And this is where the essence of filtering comes in.
An active filter IC is a type of signal processing chip that removes unwanted frequencies or noise from an input signal.
Active filters are more complex than passive analog filters, but they have several advantages.
They are faster, cheaper, and more compact than many comparable passive solutions.
In addition, active filter ICs require no external components to function properly and offer superior noise rejection.
An active filter is also known as an operational amplifier filter or OAF. An active filter IC uses amplification and feedback resistors to control the frequency response of a signal source.
If you’re interested in purchasing or developing an active filter IC for your project, keep reading for all the details you need to know about this useful piece of kit!
How do Active Filter ICs Work?
Image source tutorialspoint
The first thing you need to do is understand how active filters work. Unlike capacitive filters, active filters use amplifiers to amplify the desired frequency components of the input signal and ignore the rest. This means that an active filter can be used to remove uncorrelated noise from a signal.
Active filters are comprised of operational amplifiers (op amps), resistors, capacitors, and sometimes inductors or transformers.
The operational amplifier has two inputs. One of these receives the signal to be filtered. The other is a feedback circuit that controls the frequency response of the filter.
The feedback circuit is made up of resistors, capacitors, and inductors or transformers.
The resistive network controls the gain of the operational amplifier, while the capacitors and inductors/transformers provide frequency shaping. The output of the operational amplifier sums up the filtered input signal and the feedback circuit.
The output can be fed to an active load, like an audio speaker or a load voltage that is applied to a circuit.
Types of Active Filter ICs
As you’ve just read, there are several different types of active filters. Active filters are usually named after their function, such as low-pass, high-pass, band-pass, band-stop, etc.
Let’s look at each of the active filter IC and what it does:
Active low pass filter IC
The active low pass filter IC is used as a low-pass filter to block high frequency signals and allow low frequency signals. It is an electronic circuit that has an amplifier (i.e. op amp) that amplifies the difference between two different signals.
The output of this circuit is the output of the op amp and the difference between two different signals (i.e., input and feedback).
Active high pass filter IC
The active high pass filter IC is used as a high-pass filter to block low-frequency signals and allow high-frequency signals. In this IC, the op amp amplifies the difference between the input and feedback signals.
Active band-pass filter IC
The active band-pass filter IC is used as a band-pass filter to allow a specific frequency range to pass through. The amplifier in this IC amplifies the difference between input and feedback signals, but only for frequencies in a specific range (i.e., high or low).
This circuit is usually used for RF applications, such as cellular phones, satellite receivers, among others.
Active band stop filter IC
The active band stop filter IC is used as a band-stop filter to block a specific frequency range to pass through.
It is designed to reject both low and high frequency components.
Applications Active Filter IC?
An active filter IC is beneficial in any situation where you need to remove unwanted frequencies from a signal.
There are a few applications that are particularly well-suited to active filters, including audio circuitry, radio frequency (RF) circuitry, and power supply circuitry.
-Audio circuits: Active filters are commonly used in audio applications. When amplifiers are used to boost the gain of a weak audio signal, they also boost the noise. An audio filter reduces this noise, improving the sound quality.
-Radio Frequency circuits: Active filters are often used in RF circuits, where they are used to remove unwanted noise from the signal. This can improve the transmission quality of RF circuits.
-Power supply circuits: Active filter ICs are also commonly used in power supply circuits, where they are used to remove unwanted noise from the supply voltage. This can improve the quality of the power supply.
-In biomedical instruments: Active filter ICs are also commonly used in biomedical instruments, where they are used to remove unwanted noise from the signal and improve the accuracy of the instrument.
This is vital as most of these instruments are required to give accurate recordings at all times.
Which Active Filter IC Should You Use?
When choosing an active filter for your application, first consider the frequency range of the filter.
Ideally, you want to select a filter that can cover the entire frequency range of your application.
However, this is rarely possible, so you will need to pick a filter that covers the desired range and has sufficient headroom.
If you are using your filter in an audio application, you need to select a filter that is best suited to vocal frequencies. If you are using your filter in an RF circuit, you need to select a filter that is best suited to the transmission frequency.
If you are using your filter in a power supply circuit, you need to select a filter that is best suited to the oscillating frequency of the supply.
Key features of an active filter
To understand the importance of a dedicated IC in a filter, here are the key feature and properties of a typical active filter:
-Adequate isolation between the stages: A quality active filter should have a good amount of isolation between the stages. This prevents feedback from occurring between the stages and helps to eliminate noise and unwanted signals.
-High impedance: The input impedance of a filter should be high enough to prevent any loading of the source device.
-Low output impedance: The output impedance of an active filter must be low enough to prevent the possibility of oscillation or instability in the circuit.
-High power supply rejection: Active filters with good PSRR can filter out the noise and ripple from the power supply.
Benefits of Using an Active Filter IC
There are many advantages to using an active filter IC over a passive filter. These advantages make active filters particularly suitable for applications where a passive filter would not be suitable.
– Speed: Active filter ICs are much faster than passive filters. This means they can be used in high-frequency applications such as radio frequency circuits.
-Size: Passive filters are often bulky and require a lot of space. They can also be difficult to miniaturize. Active filters, on the other hand, can be made very compact, which makes them suitable for many different applications.
– Cost: Passive filters are much more expensive than active filters. In addition, passive components often require special care, which means they can be more difficult to use in certain applications.
– Performance: Active filters offer better performance than passive filters in many applications. This is because active filters are designed for high frequencies, whereas passive filters are not.
Limitations of an Active Filter IC
Although active filters have several advantages over passive filters, they are not suitable for every application. Active filters are more complex than passive filters, so they are typically more expensive to manufacture.
A good rule of thumb is that if your application can be achieved with a single-pole filter, it is better to use a passive filter. If your circuit requires a two-pole filter, you can use a passive filter or an active filter.
However, with a high-quality active filter IC, you will be able to minimize some of these drawbacks.
Factors to consider when choosing an active filter
When choosing an active filter for your circuit, there are several factors to consider.
-Source impedance: The source impedance is the impedance of the circuit that is providing the signal. You need to make sure that it is low enough for the circuit to work properly.
-Load impedance: The load impedance is the impedance of the circuit that is receiving the signal. You need to make sure that it is high enough for the circuit to work properly.
-Cut-off frequency: The cut-off frequency is the point at which the filter starts to remove frequencies. The higher the cut-off frequency, the better the filter is at removing high frequencies.
-Break-point: The break-point is the point at which the circuit starts to filter out frequencies. The lower the break-point is, the better the filter is at removing low frequencies.
-Steady-state error: The steady-state error is the difference between the input and output signal. As this number gets smaller, the filter is able to remove more frequencies.
-Transient error: The transient error is the difference between the input signal and output signal when there is a sudden change in frequency. As this number gets smaller, the filter will be able to respond faster to sudden changes in frequency.
-Size: If space is an issue for you, then you need to make sure that your active filter takes up as little space as possible without sacrificing quality or functionality.
Peaking vs shelving frequency response for active filters
Before you choose an active filter, you need to understand the different properties of these filters. Active filters are designed to have a specific frequency response, so you need to select a filter that is best suited to your application.
There are two main types of frequency response for active filter ICs: peaking and shelving. Peaking filters are best for applications where you want to boost a specific frequency.
Shelving filters are best for applications where you want to attenuate a specific frequency.
When choosing an active filter, you also need to consider the cutoff frequency of the filter. The cutoff frequency is the point at which the filter has reduced the signal by 3 dB.
If you want to remove a frequency, you want the cutoff frequency to be as high as possible.
This ensures that your filter completely removes the frequency. If you want to boost a frequency, you want the cutoff frequency to be as low as possible so that the filter boosts the signal at the desired frequency.
Choose a reliable active filter IC manufacturer and supplier
Choosing the right manufacturer to buy from can be difficult. When you are shopping for an active filter IC, you might come across hundreds of manufacturers.
To ensure that you choose a high-quality piece of kit, you need to know what to look for. You need to make sure that the manufacturer of your filter IC is reliable.
You can do this by reading online reviews of the manufacturer. If there are any issues with their products, you will likely find them in the reviews. Try to choose a manufacturer with a good track record.
You also need to make sure that the manufacturer of your filter IC has sufficient stock.
Active filter ICs are often used in production, so you can expect to have difficulty finding a supplier that still has the parts you need.
I hope that with this guide, you have gained valuable knowledge about active filter integrated circuits.
You know where they are used, how they are used, and how to choose the best active filter IC, vendors.
When it comes to choosing an active filter IC manufacturer in China, it is advisable to do so through a sourcing agent.
And this is where ICRFQ comes in.
We are a reputable sourcing agent for passive and active electronic components in China.
And one of the components in our catalog is the active filter IC.
Using our massive experience, we will ensure that you end up with the right IC for sale.
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