Introduction:
An active high pass filter is an electronic circuit that passes high-frequency signals with minimal attenuation and attenuates low-frequency signals. The filter achieves this by using an active component such as an operational amplifier (op-amp) in combination with passive components such as resistors and capacitors. The active high pass filter finds application in various electronic circuits such as audio signal processing, power supply filtering, and instrumentation.
Characteristics of Active High Pass Filter
- Allows high-frequency signals to pass through while attenuating low-frequency signals.
- The cutoff frequency can be adjusted by changing the values of the components or through active components such as op-amps.
- Provides gain or amplification to the filtered signal.
- Has a low output impedance.
- Has a flat response at high frequencies and a roll-off response at low frequencies.
- Used in audio amplifiers, crossover networks, and signal processing circuits.
Construction:
The active high pass filter circuit consists of an op-amp, a feedback resistor, and a capacitor. The op-amp is configured in a non-inverting or inverting amplifier mode, and the feedback resistor and capacitor are connected in series between the op-amp input and the output. The input signal is applied to the inverting or non-inverting input of the op-amp, and the output signal is taken from the op-amp output.
Working:
In an active high pass filter, the capacitor acts as a frequency-dependent impedance. At low frequencies, the capacitor’s impedance is low, which results in the signal being attenuated. At high frequencies, the capacitor’s impedance increases, which results in the signal passing through with minimal attenuation. The feedback resistor and capacitor form a high pass filter that determines the cut-off frequency of the filter. The op-amp provides gain to the input signal and compensates for the signal loss due to the filter.
Applications
Some of the applications of active high pass filters are:
- Audio signal processing in music systems and amplifiers
- Signal conditioning in sensor applications
- RF and microwave communication systems
- Instrumentation and measurement systems
- Active crossover networks in speaker systems