OA specifications used in SC Filter

[user0088]

Hello all,

Could you please advice how to choose OA specifications (dc gain, bandwidth, settling time, etc) used in SC Filter.

Thanks.

 

[varunkant2k]

Your OPAMP BW should be greater than one-decade of input switching frequency.
gain should be to follow close loop dc gain of at least 50 dB. Settling time again depends on your sampling time and amplification time requirement.

 

[user0088]

Your OPAMP BW should be greater than one-decade of input switching frequency.
.

???

If input data frequency is ,for example, 10MHz, what is bandwidth of OA (at -3db) ?

 

[user0088]

Your OPAMP BW should be greater than one-decade of input switching frequency.

What you meant? It isn't clear for me.

 

[varunkant2k]

OPAMP block in open loop stages should provide outer gain bandwidth curve. Your switched capacitor filter can operate at or below the gain/bandwidth of OPAMP. (that is fundamental rule)
Now your switching frequency if falls below BW less than decade you get gain margin error.