Digital control of an analog filter bandwidth

[Richard Webb]

I'm willing to filter a signal in 1-300 Hz or 300-4000Hz filter.
Is there a single IC component with a digital switch between the bandwidth?
I've implemented an active filter with 2 OpAmp. How can I control digitally
over the required operating range?

From your description we don't know mcuh about how you've tackled this
problem. There are two suggestions I can give. Either use a digital
potentiometer to adjust your current 2 op-amp filter. Or perhaps use a
switched capacitor filter. Maxim's website (www.maxim-ic.com) is a good
place to look for information.

 

[Pini]

I'm willing to filter a signal in 1-300 Hz or 300-4000Hz filter.
Is there a single IC component with a digital switch between the bandwidth?
I've implemented an active filter with 2 OpAmp. How can I control digitally
over the required operating range?

 

[iQbal]

I'm willing to filter a signal in 1-300 Hz or 300-4000Hz filter.
Is there a single IC component with a digital switch between the bandwidth?
I've implemented an active filter with 2 OpAmp. How can I control digitally
over the required operating range?

What you could also do is replace the gain stages with VCA.
Design a state varaible filter.
Replace the two integrators with VCA's.
Your cutoff frequency is now a function of the control voltage to the
VCA's. This control volatge could be supplied by DA.

Thats it

iQbal

 

[Tomislav Canic]

What you could also do is replace the gain stages with VCA.
Design a state varaible filter.
Replace the two integrators with VCA's.
Your cutoff frequency is now a function of the control voltage to the
VCA's. This control volatge could be supplied by DA.

Thats it

iQbal

Also, you can switch between two ranges by using 4066, 4053 or similar
analogue switch.

Rgds,
Tomislav Canic

 

[Pini]

hi,
The system will acquire analog data with input amplitudes starting with 20uV
(this signal will be amplified by 100 before filtering).
I'm afraid of noise leakage from the switch capacitor filters to the
acquired signal.
What is the solution for such problem?
The analog band pass filter footprint should be as small as possible.
Regards
Pini