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Design >> Analog Design >> papers/patents on low pass filters
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Message started by jlee on Jul 12^th, 2008, 11:32pm

Title: papers/patents on low pass filters
Post by jlee on 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 :D

Title: Re: papers/patents on low pass filters
Post by buddypoor on 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 ?

Title: Re: papers/patents on low pass filters
Post by jlee on 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

Title: Re: papers/patents on low pass filters
Post by buddypoor on 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.

Title: Re: papers/patents on low pass filters
Post by lightgo on 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. :)

Title: Re: papers/patents on low pass filters
Post by solidstate on 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.

Title: Re: papers/patents on low pass filters
Post by loose-electron on 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

Title: Re: papers/patents on low pass filters
Post by jlee on Jul 16^th, 2008, 10:30pm

Thanks! I'v got the information from your inputs