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How the RC filter work

Hey readers in this article we will see How the RC filter work with all their necessary basic information.

RC circuits generally consist of a capacitor and a resistor aligned in parallel in order to produce a constant DC power force.

RC circuits can use to filter a signal by blocking certain frequencies and allowing others to pass.

As this bias takes time for the capacitor to charge or discharge, the RC circuits are ideal to use the filters.

Know more about Phase Shift Oscillators

The RC circuit operates to filter certain signals, and this process is known as RC filtering.

RC pollutants are electronic circuits that devaluate signals outside their cut-off frequency range while transmitting signals within their range.

Depending on the arrangement, we classify filters into low-pass filters, high-pass filters, bandpass filters, and band-stop filters.

In this post, we will learn about filters low pass high pass.


Low Pass filters are setups that block high frequency and allow low frequency to pass from the input signal.

People also refer to LPF as an RC integrator. People typically build low-pass filters using simple RC (Resistor and Capacitor) networks.

To make the circuit function as an LPF, you connect a voltage directly to the resistor as shown

Low pass filter

In the above visual if the input frequence is too high the capacitor can noway reach a full discharge.

The capacitor would block the current which else will go to the affair of the circuits.

So, once the circuit crosses a particular frequency, its electrical behavior results in zero.

RC low pass filter Graph

low pass filter formulae

The voltage that’s passing through the capacitor is IXC = I/ ωC. The voltage that passes through the series combination is IZRC = I( R2( 1/ ωC) 2)1/2.

 From the above derivatives, we can write phi as

low pass filter rc

At the angular frequency ω = ωo = 1/ RC, the capacitive reactance 1/ ωC equals the resistance R.

We show this characteristic frequency w on the graph above. For instance, if R = 1 kω and C = 0.47 mF, also 1/ RC = ωo = 2.1 103rad.s- 1, so fo = ωo/ 2π = 340 Hz.

During this frequency, the gain = 1/20.5 = 0.71, as viewed on the plot of g( ω).

The power transmitted generally goes as the gain squared, so the Filter transmits half of that maximum power at fo. Now a loss in power of a factor of two means a reduction by 3 dB.

The signal with frequency f = fo = 1/2πRC degrades by 3 dB, with lower frequencies experiencing less degradation, and higher frequencies experiencing more degradation.

With this formal information one should be clear on How the RC filter work

At ω = ωo, the phase difference is π/ 4 radians or 45 °, as shown in the plot of φ( ω).


The High pass blocks the low-frequency input signal, and it allows the signals above a certain frequency to pass through the circuit.

high pass filter

The voltage through the resistor is IR. The voltage through the series combination is IZRC = I( R2( 1/ ωC) 2)1/2, so the gain g is

high pass filter formulae

The visual shows that the affair affects the input in the phase

Formerly again, when w = ωo = 1/ RC, the gain = 1/20.5 = 0.71, as shown on the plot of g( ω).

rc filter high pass

The signal with frequency f = fo = 1/2πRC undergoes a 3 dB degradation, with the advanced frequency experiencing less degradation while the lower frequency undergoes more degradation.

Again, when ω = ωo, the phase difference will be π/ 4 radians or 45degree.


Band pass RC filters used for transmitting a defined range of frequencies which blocks the frequency above or below the specified range.

People extensively use this filtering in transmitting radio frequency to pass a particular frequency and insulate the frequency piecemeal from that.


We use band-stop RC filtering to block a certain frequency in the circuit and allow other frequencies to pass through.

These pollutants are known as notch pollutants or band-reject pollutants. People extensively use these in the audio outfit to eliminate specific noise

 Operation OF RC FILTERS

  •  Audio signal processing
  •  Noise reduction in circuits
  •  Radiofrequency tuning
  •  Analog to digital conversion
  •  Designing and erecting RC filters
  •  Computations of the cutoff frequency
  •  Assembling of the circuit

Hope you are well aware of How the RC filter work.

A research paper for you to go in-depth on the same topic. Thank you for reading

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