2007-02-13 04:39:28 · 3 answers · asked by RAZOR 1 in Science & Mathematics ➔ Engineering
Ambiguous question? The bandwidth of a low pass filter is defined as the frequency at which the gain is 3dB below the DC gain. The frequency response of such a filter (on a logarithmic frequency scale) is reasonably flat from DC to the -3dB frequency, after which it slopes down linearly with a slope proportional to the order of the filter.
The filter gain automatically drops as frequency increases, that's why it is a low pass filter. I'm not sure what you mean by "why do we decrease.." the gain.
2007-02-14 14:59:53 · answer #1 · answered by kardak123 2 · 0⤊ 0⤋
Noise may be reduced, but the RATIO of signal to noise in the pass band is not necessarily reduced.
The reason I build -3dB into some passive filters is to allow better impedance matching. Filters do not have constant input impedance vs. frequency, and an input 3 dB pad makes matching the input impedance to the source easier.
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2007-02-13 05:05:22 · answer #2 · answered by tlbs101 7 · 0⤊ 0⤋
Reducing the dB gain reduces the signal to noise ratio, thus reducing noise.
2007-02-13 04:44:17 · answer #3 · answered by Grant d 4 · 0⤊ 0⤋