资料下载
A Beginner's Guide to Filter Topologies
分享资料个
represent zeros and the pn terms in the denominator represent poles. Looking at the equation， the first
thing that becomes clear is that filters that can be written in this form are biquads. This means SallenKey filters， state-variable variable filters， multiple feedback filters and other types are all biquads. There
also is a “biquad” topology to help further confuse things. Thus， the real filter names are biquad SallenKey， biquad state variable， and biquad （which will all be explained a little later）
Using low pass filters as our example， a low pass filter can be written in a general equation form as：
H（s） = K/（as² + bs + 1）， where a = R1R2C1C2 and b = R1C1 + R2C1
This can be simplified by making R1 = R2 and C1 = C2， resulting in：
H（s） = K/（R²C²s² + 2RCs + 1）
The block diagram of a low-pass 2nd order Sallen-Key filter is shown in Figure 1. This filter is also
referred to as a positive feedback filter since the output feeds back into the positive terminal of the op
amp. This topology is popular because it requires only a single op amp， thus making it relatively
inexpensive.
声明：本文内容及配图由入驻作者撰写或者入驻合作网站授权转载。文章观点仅代表作者本人，不代表电子发烧友网立场。文章及其配图仅供工程师学习之用，如有内容侵权或者其他违规问题，请联系本站处理。 举报投诉
- 相关下载
- 相关文章
