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Use of OTA in continuous time filters why not op-amp or any other active block

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HELLO

Can any one help me in understanding why OTA is used in continuous time filters. I have seen many OTA-C filters. Why not OP-amp-C filters or OTRA-C filter (Operational transresistance amplifer). Is there any particular reason of using OTA. I ahve seen op-amp based filters as well but for biomedical or low frequency applications OTA-C filters are preferred.

I cannot find any good reason of using OTA?


Thanks
 

I believe the motivation for choosing OTA-C or gm-C is discussed in the abstracts of almost any scientific paper using this filter topology. In so far the question surprizes.

gm-C active filters depend an active element with current source characteristic, usually an OTA. The term is used in contrast to active RC filters that utilize also resistors to implement poles and zeros. As far as I see, OP or transconductance amplifier based active filters aren't feasible without resistors.
 

FvM said:
I believe the motivation for choosing OTA-C or gm-C is discussed in the abstracts of almost any scientific paper using this filter topology. In so far the question surprizes.

gm-C active filters depend an active element with current source characteristic, usually an OTA. The term is used in contrast to active RC filters that utilize also resistors to implement poles and zeros. As far as I see, OP or transconductance amplifier based active filters aren't feasible without resistors.
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Thanx for your reply.

why OTA not feasible without resistors?

Because in OTA-C filters no resistors are used. If any filter like chebyshev or butterworth filter is implemented using OTA-C filter then it is doubly terminated with source and load resistors.
 

why OTA not feasible without resistors?
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??? I was talking about filter not using OTA
If any filter like chebyshev or butterworth filter is implemented using OTA-C filter then it is doubly terminated with source and load resistors.
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May be if specific a terminated passive filter structure shall be modeled, but it's not necessary to implement the filter characteristic.
 

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