What kind of OTA for gyrators in a LP Chebyshev?

[karakurto]

Hi,
I am designin a LP 5th order chebyshev filter. I am going implement inductors and resistors using OTAs.
My question is what kind of OTA I should use for that. I mean a two-stage or a folded or somethingelse? How does the OTA type or OTA specs affect the filter? What would be better for an OTA used in a filter? Roll-over frequency will be 3.5MHz and i am using UMC180 technology.
Thanks for all suggestions and valuable information!

 

[LvW]

The answer is easy. The OTA structure should come close to the ideal OTA as much as possible. That means - high input impedance and high output impedance.
As all design formulas and strategies are based on ideal OTA properties (VCCS) , all OTA parameters which do not correspond to these assumptions will disturb the filter function. Good (i e. nearly ideal) OTA parameters will lead to deviations which are in most cases acceptable.