Filter circuits are used to **pass only certain frequency** components. In an RC Low Pass Filter (LPF), only LOW-frequency components from the input signal are passed to output, whereas HIGH frequencies get attenuated. This article gives an idea about low-pass filters using **resistor-capacitor** combination (RC Filter).

Op-amp low pass filters are also used to decrease the slope or to get a **sharp cutoff frequency** along with **amplification**. We had discussed **Op-Amp Low Pass Filter already.**

Here is the most simple but common filter circuit using an RC network with frequency response. The given waveform shows decreasing gain with increasing frequency.

## RC Low Pass Filter Circuit

## RC Low Pass Filter Design

## Components

- Resistor
- Capacitor
- Signal Generator
- Breadboard

(Values depend on the design)

## LOW Pass Filter (LPF) Working

- It allows the passing of low-frequency components and attenuates high-frequency components in the input signal.
- The capacitive reactance is given by, Xc=1/(C(2πf). That is capacitive reactance decreases with an increase in frequency (Inversely proportional).
- Now at higher frequencies, the capacitor acts as a virtual short circuit that directs the input signal amplitude to the ground. Thus the output falls to zero.
- At lower frequencies capacitor acts as an open circuit, and the entire signal appears at the output.
- By observing the above waveform you can see that the amplitude decreases with an increase in frequency.

## Frequency Response of RC Low Pass Circuit

## RC Low Pass Filter working as an Integrator

- The same circuit can be treated as an Integrator.
- An integrator does the mathematical operation ‘
**Integration**‘ of the input signal.

- When pulse waveform is applied to the circuit, the capacitor charges through the resistor, and hence the output voltage builds up.
- When the input is removed (ground potential), the capacitor starts to discharge.
- Thus we get a triangular waveform.

- As the value of RC increases the amplitude of the output decreases (See above fig) because it takes more time to charge and discharge.

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