Saturday, July 13, 2013

Low Pass Filter

The simplest low-pass filter circuit is nothing more than a resistor and capacitor:
Low-frequency voltage signals applied to this circuit emerge at the output terminal relatively
unattenuated, because the reactance of the capacitor is quite large at low frequencies. High-frequency
signals applied to the same circuit become attenuated by the capacitor, which tends to “short” those
signals to ground with its low reactance to high frequencies. The performance of such a filter circuit
is primarily characterized by its cutoff frequency, mathematically defined as
 The cutoff frequency is the point at which only 70.7% of the input signal appears at the output (a -3 dB attenuation in voltage).

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