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# RC Low Pass Filter Explained

In this video, passive RC low pass filter has been discussed.

What is electronic filter:

The electronic filter is the circuit, which passes some range of frequencies of the input signal and rejects or attenuates the unwanted frequencies in the signal.

Based on the range of frequencies which is being passed by the filter, there are 4 different types of filter.

1) Low Pass Filter

2) High Pass Filter

3) Band pass Filter

4) Band Reject Filter

What is Low Pass Filter:

A low-pass filter is the electric circuit, which passes the low range of frequency signals, starting from 0 Hz (DC) to up to the cut off frequency (fc), and rejects all other frequencies which are higher than cut off frequency.

Now, based on the components used for the design, this low pass filters further can be classified into 2 categories.

1) Active Low Pass Filter:
If the low filter is designed using the active components like Op-Amp and transistors then such filters are known as active low pass filter.

2) Passive Low Pass Filter:
If the low pass filter is designed using the passive components like R, L and C then such filters are known as passive low pass filters.

These are the most common types of Passive Low Pass Filters.

1) RC Low Pass filter
2) RL Low Pass Filter
3) RLC Low pass filter

So, in this video first order RC Low pass filter has been discussed and at the later part of the video, it is shown that how by cascading first order low-pass filters, we can design higher order filters.

The order of the filter can be defined by the number of poles in the transfer function of the filter.
(One simple way to find the order of the filter is to calculate the number of reactive components in the circuit, i.e capacitor, and inductor, but always it is not true. There might be some exceptions)
But in general, this procedure can be followed.

The time-stamped link for the different topics in the video is given below:

0:27 What is an Electronic filter? Different types of Electronic Filter

2:46 RC Low Pass Filter

5:12 Derivation of cut-off frequency expression

8:35 Example on Low Pass Filter

12:28 Higher order filter design by cascading first order filters

This video will be helpful to all students of science and engineering in understanding the RC low pass filter.