Lilylily wrote on Aug 19th, 2009, 2:15am:Hi,everyone,I have to design two filters having cutoff frequencies of 100kHz and 1.2Mhz. And I don't know how to select the amplifiers in the filters. And what is the requirement on the gain, bandwidthand so on?Thanks!!
This really depends on your requirements. I would advise using a simple (but reasonably realistic) opamp model and playing around withthe gain/bandwidth/slewrate etc. to see what the minimum requirements are, and then setting your spec to be a bit higher than that (safety margin).
For continuous-time filters, it is quite easy to do this exercise. There is also something called "sensitivity analysis" which you can use. This is available with the Cadence Analog Design Environment for Spectre, but I have never used it yet. You can try it out with a schematic of your filter containing some opamp macromodels to see if you get something useful out of it.
Best regards,
Vivek