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jlee

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papers/patents on low pass filters
Jul 12^th, 2008, 11:32pm

Hi Guys,

I am searching papers/patents on low pass filters with very low -3dB frequency.

In order to decrease chip area, small capacitance and large resistance are used. The resistor is implemented by MOS transistor operated in subthreshold region.

Does anybody know the detail information about these papers or patents?

Thanks for your feedback in advance.

Regards

Jason Cheesy

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buddypoor Community Fellow Offline Posts: 529 Bremen, Germany	Re: papers/patents on low pass filters Reply #1 - Jul 13^th, 2008, 1:58am As your mosfets are operated below threshold (weak inversion) I understand that you are interested in information about log-domain filters. Is this corect ?
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jlee Community Member Offline Posts: 40	Re: papers/patents on low pass filters Reply #2 - Jul 13^th, 2008, 5:51am Thanks for your input, buddypoor. What's log domain filter? Actually, I am realy interested in how to implement a large resistor, say 10M ohm, with MOSFET operated in subthreshold region. I just want to search some papers or patents on this subject to get some design insights. Regards Jason
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buddypoor

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Posts: 529
Bremen, Germany

Re: papers/patents on low pass filters
Reply #3 - Jul 13^th, 2008, 6:54am

Well, here is some background information about log-domain-filter:
With the aim to lower supply voltages and power consumption, it is possible to use MOSFETS below threshold (weak inversion) using their nonlinear properties and to correct the introduced distortions thereafter.
This is something like compression/expansion (companding) and is applied exclusively in integrated form.
But I�m not sure if you have asked for such a modus to provide active filtering.

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LvW (buddypoor: In memory of the great late Buddy Rich)

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lightgo New Member Offline Posts: 6	Re: papers/patents on low pass filters Reply #4 - Jul 14^th, 2008, 6:34am Is that Yong? if yes, you can login Bo's computer and find the documents you want on the desktop.
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solidstate Junior Member Offline Posts: 16 Munich, Germany	Re: papers/patents on low pass filters Reply #5 - Jul 15^th, 2008, 11:18am Hi, I've used this successfully: J. A. Geen, S. J. Sherman, J. F. Chang et al., �Single Chip Surface Micromachined Integrated Gyroscope With 50�/h Allan Deviation,� IEEE J. Solid-State Circuits, Dec. 2002.
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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: papers/patents on low pass filters Reply #6 - Jul 15^th, 2008, 5:25pm Tsividus is the well published whiz kid on what are known as "MOSFET - C" filters. �Google it or look in IEEE JSSC or IEEE Xplore- they do lack dynamic range and have linearity issues, but they are a useful methodolgy in some cases. A quick look shows about 50 papers on the IEEE Xplore search Jerry
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jlee Community Member Offline Posts: 40	Re: papers/patents on low pass filters Reply #7 - Jul 16^th, 2008, 10:30pm Thanks! I'v got the information from your inputs
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