Active Low-Pass Filter

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03:31:49

An operational amplifier with feedback becomes an active low pass filter by adding a capacitor in parallel to feedback resistor.

Amplifier Output = - Input times ( Feedback Resistor / Input Resistor)

So,  1 volt x (4 k / 1 k) = 4 volts amplifier output

Cutoff Frequency = 1 / (2 x pi x Feedback Resistor x Frequency Capacitor)

Then, 1 / ( 2 x 3.1459 x 4,000 x .0000000002 ) = 19,867.1286 cutoff frequency

When we reach frequency when capacitive resistance equals resistance of feedback resistor, the total reactance is 0.707 of the resistor and output is at -3-dB point known as the cut off frequency.

published 2 years ago

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