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blue111

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Re: Question about gyrator implementation of active inductor
Reply #15 - May 04^th, 2018, 10:00am

Quote:

If you inject a current into node X, the feedback loop will respond to adjust the voltage on CL until the 2nd gm stage absorbs all of that current. This gives you a low impedance at low frequencies. How low? Just 1/(gm1*rout1*gm2). I.e. 1/total_gm.

I do not understand what you mean by "2nd gm stage absorbs all of that current"

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blue111 Community Member Offline Posts: 81	Re: Question about gyrator implementation of active inductor Reply #16 - May 13^th, 2018, 9:38am @Dan Could you comment on https://www.eevblog.com/forum/beginners/help-in-deriving-zin-small-signal-expres... ?
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blue111 Community Member Offline Posts: 81	Re: Question about gyrator implementation of active inductor Reply #17 - May 22^nd, 2018, 8:04pm Quote: With the large transistor dimensions chosen in this design, the gyrator input-referred offsets are less than 6 mV For https://cloudfront.escholarship.org/dist/prd/content/qt1pg6p6nb/qt1pg6p6nb.pdf?t... , how is large transistor dimension related to input-referred offsets ?
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danmc

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Re: Question about gyrator implementation of active inductor
Reply #18 - May 23^rd, 2018, 10:42am

google MOS transistor matching or look in any of the standard text books on analog circuit design about matching. "Analysis and Design of Analog Integrated Circuits" by Gray&Meyer (now Gray, Hurs, Lewis, and Meyer) or really any of the others should have a discussion about this. I'm sure you can find many lecture notes online.

I'm curious as to what your application is for the gyrator? Is this a class project?

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blue111 Community Member Offline Posts: 81	Re: Question about gyrator implementation of active inductor Reply #19 - Jun 1^st, 2018, 10:23pm Do you guys have any idea how to select mosfet sizing of asymmetric differential pair (Gm2 transconductance circuit block) for maximum output impedance ? I have derived the Rout expression at http://www.eevblog.com/forum/beginners/help-in-deriving-zin-small-signal-express...
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Horror Vacui Senior Member Offline Posts: 127 Dresden, Germany	Re: Question about gyrator implementation of active inductor Reply #20 - Jun 5^th, 2018, 1:29am TLDR; gm and output impedance can be separated. You can put cascodes to increase the output impedance, while the gm stays the same.
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