Low Pass Filter: LPF using Op-Amp & Applications

A filter can be defined as; it is one kind of circuit used for reshaping, modifying, and otherwise rejecting all unwanted frequencies of a signal. An ideal RC filter will divide & allows passing input signals (sinusoidal) depending on the frequency. Generally, in low-frequency (<100 kHz) applications, passive filters are constructed using resistor and capacitor components. So it is known as a passive RC filter. Similarly, for high-frequency (> 100 kHz) signals passive filters can be designed with resistor-inductor-capacitor components. So these circuits are named as passive RLC circuits. These filters are so called based on the range of frequency of the signal which they let to pass them. There are commonly three filter designs are used such as low pass filter, high pass filter, and bandpass filter. This article discusses an overview of the low pass filter.

What is a Low Pass Filter?

The definition of low pass filter or LPF is one kind of filter used to pass signals with low frequency as well as attenuate with high frequency than a preferred cut-off frequency. The low pass filter frequency response mainly depends on the Low pass filter design. These filters exist in several forms and give the smoother type of a signal. The designers will frequently use these filter like a prototype filter with impedance as well as unity bandwidth.

The preferred filter is acquired from the sample by balancing the preferred impedance, and bandwidth, & changes into the preferred band type like low-pass (LPF), high-pass(HPF), band-pass (BPSF)  or band-stop(BSF).

First Order Low Pass Filter

A first-order LPF is shown in the figure. What is this circuit? A simple integrator. Note that integrator is the basic building block for LPFs.

First Order Low Pass Filter
First Order Low Pass Filter

Assume Z1 =1/

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