Active High Pass Filter

Active High Pass Filter
Active High Pass Filter

The active high-pass filter is a basic electrical circuit that passes signals above a cutoff frequency and attenuates signals below it. It removes low-frequency noise and distortion, making it crucial in many audio and communication systems. A precise frequency response from the active high pass filter provides output signal integrity and quality. Audio processing, telecommunications, and instrumentation require knowledge of this filter’s purpose, operation, and uses.

Use of Active High Pass Filter

The active high pass filter selectively passes high-frequency impulses while attenuating low-frequency ones. An operational amplifier (op-amp) and passive components like resistors and capacitors accomplish this. The active high pass filter can improve signal quality by blocking low-frequency noise, DC offsets, and interference with an adequate cutoff frequency. Audio equalizers, speaker systems, crossover networks, and high-frequency signal processing use it.

Active High Pass Filter
Active High Pass Filter

Active High Pass Filter Uses

An Active high pass filters are used in many fields. They amplify or highlight high-frequency material in audio systems, improving sound clarity. Speaker protection circuits use these filters to prevent low-frequency signal harm. Telecommunications use active high pass filters to remove low-frequency noise and data transmission interruptions. Biomedical instruments use them to filter out undesirable signals and noise from physiological measures. In addition, scientific instrumentation, radar, and control systems use active high pass filters to reduce low-frequency interference and increase performance.

How Do Active High Pass Filters Work?

An active high pass filter amplifies the input-output difference using an op amp. Op amps increase higher frequencies you want to pass. While blocking lower frequencies, it attenuates them.

The main parts of an active high pass filter are:

  • Capacitors pass higher frequencies but block lower frequencies. Cutoff frequency depends on capacitor value.
  • Control filter gain and frequency response with resistors.
  • Op amps boost input-output differences. Higher frequencies over the cutoff frequency are boosted.
  • By changing the resistors and capacitors, you may set the filter’s cutoff frequency. Above the cutoff, frequencies pass through; below, they are muted. Higher cutoff frequencies allow more high-frequency transmissions.
  • Active high pass filters feature a sharper cutoff, higher input impedance, and lower output impedance than passive ones. Higher gain and wider cutoff frequencies are also common. Passive filters do not need power to run the op amp, whereas active filters need.

In conclusion, an active high pass filter amplifies high-frequency sounds while inhibiting low-frequency ones. Op amps, resistors, and capacitors control the cutoff frequency and produce a crisp frequency response. Audio processing, instrumentation, and communication systems use active high pass filters to isolate high-frequency signals.

Active high-pass filters work

Active high pass filters use an amplifier and capacitor to pass high-frequency signals but block low-frequency ones.

Component Interactions

The circuit for an active high pass filter uses an op-amp and a capacitor. The capacitor filters low frequencies while the op-amp boosts the incoming signal.

For high frequencies, the capacitor has low resistance, while for low frequencies, it has high resistance. At high frequencies, the capacitor easily outputs the signal. The capacitor inhibits low-frequency signals from reaching the output.

Adjusting capacitance changes the filter’s cutoff frequency, which blocks signals. Higher cutoff frequencies allow higher frequencies to pass with lower capacitance. Higher capacitance lowers the cutoff frequency, blocking more high frequencies.

Why Use Active Filter?

Active high pass filters have advantages over passive ones:

They buffer and gain voltage. Op-amps boost signals and prevent filters from loading down input signals.

The cutoff is sharper than most passive filters. The filter transitions from passing to blocking frequencies more abruptly due to op-amp feedback.

Their tuning range is vast. Adjusting the capacitor lets you set the cutoff frequency to several values. Passive filters have narrower tuning ranges.

Operating the op-amp requires power. Power can be a drawback, yet it adds amplification, buffering, and tuning range.

An active high pass filter filters out low-frequency signals while amplifying and passing higher-frequency frequencies. Adjust the cutoff frequency to suit your needs.

Application of Active High Pass Filter

Activated high pass filters have several uses. These filters pass high-frequency transmissions but block low-frequency ones.

Audio equalization

Active high pass filters help reduce popping and rumbling in audio systems. They clearly transmit music and vocals at higher frequencies. Stereo audio equalizers contain high pass filter options to reduce low bass frequencies that muddy the sound.

Impedance matching

In electronic systems, active high pass filters match circuit or component impedance. For optimal circuit power transfer, impedance matching is crucial. A high pass filter with a defined cutoff frequency can block low-frequency noises that some components cannot withstand. This prevents power loss and passes the most relevant frequencies between components.

Remove DC offset

Power supply and other components can cause DC offsets, undesirable low-frequency signals in electronic circuits. To avoid system AC signal interference, these DC signals must be filtered. An active high pass filter with a low cutoff frequency, frequently below 1 Hz, can prevent DC offset signals while passing higher-frequency AC impulses.

Conditioning sensor signals

Before processing or analyzing signals from vibration, pressure, or temperature sensors, signal conditioning is often needed. To isolate a frequency band or remove low-frequency noise from the sensor data, an active high pass filter can be utilized. After filtering, various electrical components can process the signal.

Active high pass filters let you customize signals for these applications. An Active high pass filters can increase audio quality, power transfer, noise reduction, and frequency isolation in electronic signal processing.

Active High-Pass Filter Circuit Design

An active high pass filter passes high-frequency signals but blocks low-frequency ones. The following components are needed to create an active high pass filter circuit:

Working Amplifier

Circuit heart is the op amp. To produce an output, it magnifies the input difference. An op amp with the required frequency range can be used for an active high pass filter.

Resistors, Capacitors

Resistors and capacitors create high-pass filters. The resistor lets high frequencies into the op amp, while the capacitor inhibits low frequencies.

Select a high capacitance capacitor (0.1 μF to 10 μF). Large capacitance lowers cutoff frequency, blocking more low frequencies.

Capacitance and resistor value determine cutoff frequency. Higher resistors reduce cutoff frequencies. Common values range from 1 to 100 kΩ.

Cutoff Frequency

The filter blocks frequencies at the cutoff frequency. It relies on resistor and capacitor values, per formula:

Cutoff frequency = 1/(2πRC)

R is the ohm resistor and C is farad capacitance.

Extra Points

  1. Parallel the capacitor to the input signal. The resistor connects the capacitor and op amp input.
  2. Connect the op amp output to the inverting input for negative feedback. This stabilizes gain.
  3. Change resistors to adjust the gain. Higher gain provides a stronger cutoff frequency change.
  4. Higher frequency ranges require lower capacitance. A tradeoff is lower low-frequency attenuation.

Choose components to obtain your desired cutoff frequency and gain to create an active high pass filter circuit. Have more questions? Let me know!

Selecting an Active High Pass Filter

To find the correct active high pass filter for your audio equipment or circuit, examine a few variables.

Cutoff Frequency

Filter cutoff frequencies determine which frequencies are blocked. Lower cutoff frequencies like 10Hz block only very low bass. A higher cutoff like 1000Hz blocks more low and midrange frequencies. Choose a cutoff frequency based on the frequencies to filter. A cutoff between 50 and 200Hz reduces rumbling and hum in most audio applications without affecting the audible frequency range.


The slope, or rolloff, is how steeply the filter decreases frequencies below the cutoff point. Filters with a 12 or 24 dB/octave slope block frequencies more strongly, whereas those with a 6dB slope roll off more gradually. Steeper slopes filter low-frequency noise better. For telephone or radio emulation, a gentler slope may sound more natural.

Filter Type

The most common active high pass filters are Butterworth, Bessel, and Chebyshev. Butterworth filters response is flat and smooth in the passband. Bessel filters replicate quick transient sounds correctly due to impulse response optimization. Chebyshev filters feature the steepest rolloff but an uneven passband. Choose according to how correctly you need to recreate passband signals against how forcefully you need to block stopband frequencies.

By evaluating these criteria and choosing specs that suit your audio application or circuit, you can choose an active high pass filter with the frequency response and performance you need. The right filter can reduce noise, increase sound quality, or change tones.


That covers active high pass filters’ operation. You now comprehend their function and circuit applications. Active high pass filters are adaptable and can block low-frequency signals or be used as basic filters. They may seem complicated, but break them down step-by-step to understand. You’ll design filters quickly with practice. Don’t hesitate—use your knowledge! Who knows what cool filters you’ll make.

Be the first to comment

Leave a Reply

Your email address will not be published.