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Design >> Analog Design >> Capacitor spread in SC filters
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Message started by rampat on Dec 30^th, 2007, 8:45pm

Title: Capacitor spread in SC filters
Post by rampat on Dec 30^th, 2007, 8:45pm

Hi all,

In one of my sc-HPFr the cap spread is coming out to be 70..Can I go ahead with this number.?Is there any issue?.I cant reduce this number because the sampling frequency is 1.5MHz and filter cutoff frequency is 50Hz.So please suggest me

thanks

Title: Re: Capacitor spread in SC filters
Post by vivkr on Jan 4^th, 2008, 2:37am

Hi,

If there is no possibility to change anything in the system, then you have to live with this number. However, depending on the signal
bandwidth of interest, you might be able to adjust things.

What is the signal band of interest? If you are only dealing with relatively low frequencies, then I would recommend dividing the
clock down to a lower frequency which would still fulfil your requirements. You will save both power and area that way.

If the 50 Hz limit is not a very tight one, and depending on other constraints, you might be able to realize the HPF using
gm-C filter techniques rather than SC. This only works if you are willing to accept a relatively large variation in cutoff
frequency (+/- 30% say).

Regards
Vivek