lavpassfiltre

A lavpassfiltre, or low-pass filter, is an electronic circuit or digital algorithm that passes signals with frequencies below a chosen cutoff frequency while attenuating signals with frequencies above that threshold. The most common reference point is the cutoff where the output power is reduced by half, often expressed as −3 decibels. Real filters have a transition band and finite attenuation in the stopband.

Analog implementations include passive RC networks and active filters using operational amplifiers. A simple first-order lavpassfiltre can be built from a resistor and a capacitor, with the cutoff frequency f_c determined by f_c = 1/(2πRC). Higher-order filters achieve steeper roll-off by cascading sections or employing active topologies such as Sallen–Key or multiple-feedback configurations, which can improve impedance behavior and gain control while preserving stability.

In digital systems, a lavpassfiltre is realized by discrete-time processing and can be implemented as IIR (infinite impulse response) or FIR (finite impulse response) filters. Design goals include a flat passband, a sharp transition band, and adequate stopband attenuation. Common families include Butterworth (maximally flat passband), Chebyshev (allowing ripple for steeper skirts), and Bessel (linear phase). Design is followed by discretization, often via bilinear transform or impulse invariance.

Applications span audio processing, anti-aliasing and anti-imaging for analog–digital conversion, data conditioning in sensors, and various communications and control systems. Key considerations include phase response and group delay in precise timing contexts, component tolerances in analog implementations, and sampling rate and numerical precision in digital designs.