Difference between revisions of "Second Order Active Filters"
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2nd order active filtering has two main advantages: |
2nd order active filtering has two main advantages: |
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1) High impedance input, low impedance output |
*1) High impedance input, low impedance output |
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2) greater attenuation at high range (-40dB/decade as opposed to -20dB/decade for RC filter) |
*2) greater attenuation at high range (-40dB/decade as opposed to -20dB/decade for RC filter) |
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The high impedance provided by an op amp circuit protects the instrument providing the signal from passing excessive current which could cause a voltage drop in the measurement signal or damage to the instrument itself. |
The high impedance provided by an op amp circuit protects the instrument providing the signal from passing excessive current which could cause a voltage drop in the measurement signal or damage to the instrument itself. |
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Revision as of 18:34, 8 December 2008
2nd order active filtering has two main advantages:
- 1) High impedance input, low impedance output
- 2) greater attenuation at high range (-40dB/decade as opposed to -20dB/decade for RC filter)
The high impedance provided by an op amp circuit protects the instrument providing the signal from passing excessive current which could cause a voltage drop in the measurement signal or damage to the instrument itself.
Because the filter is second order, the rolloff before/after the cutoff frequency or frequencies on a bode plot is -40 dB/decade as opposed to -20 dB/decade for a first order (RC) filter which means significantly greater attenuation outside the pass band and a sharper cutoff which can be very useful if the noise frequency is close to the desired signal frequency.
