Active RC Filter design questions about OPAMP

[Harks]

Active RC Filter design

Hi, all,

I am designing an active RC filter. I am wondering if anyone can tell me the relationship between filter corner frequency and OPAMP's gain bandwidth.
In addition, what is the OPAMP DC gain needed if the filter is 0dB butterworth LPF?

That is, how should I define the opamp spec. when designing an active RC filter?


Thanks

 

[cqmyg5]

Active RC Filter design

I meet same problem, please give a hand.

 

[richloo]

Active RC Filter design

The desired filter corner frequency must fall within the unity gain bandwidth of your opamp.
So that u can meet the cutoff frequency when u design the 0dB(unity gain) LPF in close-loop.

Open-loop gain of the opamp should be as high as possible (~60dB).

 

[Hero]

Re: Active RC Filter design

For best performances use some BiMOS OP amp. They have high gain, CMRR and input resistance and small drift and leakage input current.

 

[willyboy19]

Re: Active RC Filter design

What really matters is the gain-bandwidth-product of the opamp you are using -- they should be usually 10x larger than your desired filter corner frequency to minimize Opamp's finite GBW effect on your active filter.

 

[cqmyg5]

Re: Active RC Filter design

What really matters is the gain-bandwidth-product of the opamp you are using -- they should be usually 10x larger than your desired filter corner frequency to minimize Opamp's finite GBW effect on your active filter.

10x is enough or not? I saw somebody said it must be 100x.

 

[GDF]

Re: Active RC Filter design

Please refer to th"OPamp for everyone" published by TI.
The suggested DC gain at corner frequency is around 40dB gain.
The gian will affect your accuracy of corner frequecy and filter gain.