HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Blogs
Guest Blogs

Switched-Capacitor Filters: An Introduction

View Comments: Threaded|Newest First|Oldest First
Cabe Atwell
User Rank
Blogger
app
Cabe Atwell   6/11/2013 5:20:43 PM
NO RATINGS
Jon,

Can you suggest some applications for the filter you describe?

C

Jon Titus
User Rank
Blogger
Switched-Cap Filter Applications?
Jon Titus   6/11/2013 5:41:48 PM
NO RATINGS
You will find switched-capacitor filters (SCFs) in audio circuits, in anti-aliasing filters, and in tracking filters. The latter type of filter can track a signal by adjusting the filter's clock frequency to "tune" filter characteristics as a sampled signal changes frequency. You also can use SCFs in tone-detection circuits. Unlike a PLL circuit that requires external passive components (and trimming) to detect a tone, an SCF requires only a clock signal. SCFs also serve as notch filters.

Because the filtering occurs based on a "master" clock signal's frequency, you might consider an SCF is you want to scan a given bandwidth to obtain information within it at certain frequencies.  The SCFs would act like the front end of a spectrum analyzer.

AnandY
User Rank
Gold
Capacitor ratios
AnandY   6/12/2013 5:16:08 AM
NO RATINGS
So, for an SCF, the frequency response depends solely on the ratio of two capacitors, C and C1, and the switching-clock frequency, fclk.

@Jon, thanks for the very informative post. Capacitor ratios can take advantage of the superior matching of capacitances fabricated on silicon. Especially in monolithic form capacitor ratios are very robust against changes in temperature.

AnandY
User Rank
Gold
Silicon area
AnandY   6/12/2013 5:22:50 AM
NO RATINGS
In a SCF, capacitors and switches take the place of resistors...

High-value resistors can be implemented in very little silicon area. For example, a 1-Mohm resistor can be realized with a 1-pF capacitor switched at a clock rate of 1-MHz.

Partner Zone
More Blogs from Guest Blogs
It seems that gears have been around forever -- what could be new?
The use of ZNE technology buildings not only reduces cost and creates renewable energy, but it can give a boost to the economy. The implementation and execution will require a workforce, which means the result can be increased employment.
The use of CFD is more profound in automobile design because of the diverse physics involved. It can be used to optimize components for downsizing and reducing the environmental footprint while maintaining or improving operational efficiency.
A Detroit automaker was struggling with a semi-manual, labor-intensive parts receiving process. Workers had enter parts into a spreadsheet manually at a stationary workstation. This stopped the receiving process dead in its tracks. A better system was needed.
Pressure sensors can be used in a wide range of applications. Its imperative that theyre suited for use in hazardous situations and are fully compliant with one of several protection standards.
Design News Webinar Series
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
7/17/2014 11:00 a.m. California / 2:00 p.m. New York
6/25/2014 11:00 a.m. California / 2:00 p.m. New York
5/13/2014 10:00 a.m. California / 1:00 p.m. New York / 6:00 p.m. London
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Aug 4 - 8, Introduction to Linux Device Drivers
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Class: August 12 - 14
Sponsored by igus
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service