Transconductor frequency limitation on gm-c filter?

[ezbentley]

For op amp filters, the op amp itself must have a unity gain frequency much higher than the operating frequency of the op amp filter.

Is there a similar constraint on transconductor and gm-c filter? If so, how do I quantify the relationship?

For example, if I want to design a gm-c filter at 100MHz, what kind of frequency response is required for the transconductor?

 

[montage3000]

what your tolerance?

 

[ezbentley]

Tolerance is not a major issue. My boss wants me to "try" to design one and see if it's any useful. No one at my work knows much about active filter. @@

 

[pfd001]

The gm cell work in open loop, there is a difference from opamp in close loop. for gm cell, you should check the frequency response in filter level

 

[ezbentley]

If a gm cell works in open loop, then how is the bias of the input determined? From the way the gm cells are used in gm-c filters, it doesn't seem like the gm cells are internally bias.

 

[sixth]

If a gm cell works in open loop, then how is the bias of the input determined? From the way the gm cells are used in gm-c filters, it doesn't seem like the gm cells are internally bias.

You can build up a simple Gm-C integrator with a first order approximate Gm cell and then write its transfer function. Comparing with the ideal one, you will find the rule.

 

[pfd001]

The bias of the input can be made to make sure that you can get a constant gm in a large input signal range.

 

[loose-electron]

This, as stated elsewhere is all about the bandwidth of the transconductor.

I have done gm-C filters with 250MHz bandwidth for filters in the receiver front end for UWB chips.

Jerry

www.effectiveelectrons.com
"chips that work"

 

[2steps]

I agreed with sixth's option