Is it feasible to achieve 1 MHz cut-off frequency

Re: Filter

Is it feasible to achieve 1 MHz cut-off frequency through sallen-key active RC filter on chip?
If possible, what should the minimum order of the filter be?

Added after 2 hours 36 minutes:

One More question regarding SK filter: What kind of stability issues one might encounter while designing such a filter? I couldn't find any paper which explains this in little bit depth. Please help!!!

Re: Filter

samiran_dam said:

Is it feasible to achieve 1 MHz cut-off frequency through sallen-key active RC filter on chip?
If possible, what should the minimum order of the filter be?

Added after 2 hours 36 minutes:

One More question regarding SK filter: What kind of stability issues one might encounter while designing such a filter? I couldn't find any paper which explains this in little bit depth. Please help!!!

Click to expand...

Of course, it is possible. However, you need an opamp with a minimum unity gain bandwidth (UBW) of app. 50...100 MHz. It depends on the error in the filter response you allow.
The required order depends on the damping requirements. You can have a cut-off of 1 MHz with a 1st order or (if you like) with a 6th order filter.
Do you have no requirements concerning ripple in the passband (filter approximation)?
What do you mean with "stability issues"? For a filter in the MHz range possible stability problems are caused mainly by parasitic effects.

1. Do you have no requirements concerning ripple in the passband (filter approximation)?

Actually I am upto butterworth approximation, so maximally flat response of b'worth keeps me away from dealing with passband ripple.

2. What do you mean with "stability issues"?

By stability issues I meant that, does the phase margin of LPF's response cause any kind of problem / op-amp's capability to handle a limited range of its own input signal puts any unbounded output problem (I am not sure of this just intuitively guessing) / Or any non-linearity (other than the slew-rate as you have discussed) causes distortion/harmonic effect on the output signal?

If possible, please elaborate/refer any paper for the parasitic effect as you have mentioned.

By stability issues I meant that, does the phase margin of LPF's response cause any kind of problem

The pole Q of each filter stage (by the way: which order do you require?) corresponds to a specific margin. As larger the Qp value as smaller the margin. But that is quite normal as it belongs to the filter characteristic. The only point you have to be careful is the opamp transfer charactristic. It must be unity gain stable!


/ op-amp's capability to handle a limited range of its own input signal puts any unbounded output problem (I am not sure of this just intuitively guessing)

Of course, the input range is limited. In this context, it is important to know which gain requirements for the filter exist.

/ Or any non-linearity (other than the slew-rate as you have discussed) causes distortion/harmonic effect on the output signal?

As for each opamp application: As lower the output signal as smaller the distortion.