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op-amp input frequency maximum

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djalli

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opamp input frequency

I recently designed an opamp-based active filter lowpass as 10kHz. This opamp has bandwidth 20Mhz according to datasheet.
Is this filter si going to filter well 100Hz component out of a signal 30Mhz I insert?
 

flatulent

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op-amp and frequency

The filter will not produce the theoretical attenuation at 30 MHz, but there will be some attenuation. If you have an odd number of poles so the first stage is a series R shunt C network this will produce a lot of attenuation at 30 MHz. You can also precede your active filter with a LC type with a convenient cutoff much higher than 100 Hz, but much lower than 30 MHz.
 

djalli

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flatulent said:
The filter will not produce the theoretical attenuation at 30 MHz, but there will be some attenuation. If you have an odd number of poles so the first stage is a series R shunt C network this will produce a lot of attenuation at 30 MHz. You can also precede your active filter with a LC type with a convenient cutoff much higher than 100 Hz, but much lower than 30 MHz.

Yes you are absolutely right. Preciding with rf choke-shunt did make the magic. Many thanks flatulent
 

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