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Filters
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Low-pass, high-pass and band-pass circuits.
RC and RL combinations pass some frequencies and block others: low-pass (capacitor to ground), high-pass, band-pass. Cutoff f_c = 1/(2πRC).
R = 1 kΩ, C = 0.16 μF: f_c = 1 kHz.
Roll-off is 20 dB per decade for first order.
In more detail
Electronic filters pass some frequencies and block others, using combinations of resistors, capacitors and inductors. Low-pass, high-pass, band-pass and notch filters are common types.
Real-world uses
- Audio crossovers direct low frequencies to woofers and high frequencies to tweeters.
- Power supplies use low-pass filters to remove ripple.
- Audio systems use low-pass filters to send bass to the woofer and high-pass filters to send treble to the tweeter.
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Frequently asked questions
What is a cut-off frequency?
The frequency at which the output power falls to half its maximum.
Which filter removes hum?
A notch filter, tuned to the mains frequency.
What does a low-pass filter do?
It lets low frequencies through while attenuating high frequencies.
Related topics in AC Circuits & EM Waves
Wattless current · LC oscillations · Parallel resonance · Transformers in power transmission · Three-phase power · Rectification and smoothing