Re: Loading Effect in Feedback

From: Zhiheng Cao (cao_at_ece.utexas.edu)
Date: 12/08/04 

Date: Wed, 8 Dec 2004 14:36:04 -0600

Thanks for the pointer, but can one calculate
terminal impedance modified by feedback using the Middlebrook's
method? As far as I know that method is used to find out the
open loop gain Ab.

"Jim Thompson" <thegreatone@example.com> wrote in message
news:uv6er0t1b0lm0a258c2ml3o1cj55leiglj@4ax.com...
> On Tue, 7 Dec 2004 20:09:52 -0600, "Zhiheng Cao" <cao@ece.utexas.edu>
> wrote:
>
> >I am a student studying analog circuits and I am having hard time
> >understanding loading effect in feedback.
> >
> >Some books say when we cut the loop, we need to load
> >the output of the opamp with feedback network beta and the opamp input
> >behind it, but we can set the voltage (by the feedback) at the opamp
> >input using an ideal voltage source.
> >
> [snip]
> >
> >I am sorry if my explanation is too confusing.
> >
> >Thank you for reading my post.
> >
>
> Look up Middlebrook's method, where the loop is NOT broken.
>
> Then study the LOOPGAIN part on my website. The part implements the
> Middlebrook procedure for use in a Spice simulator.
>
> ...Jim Thompson
> --
> | James E.Thompson, P.E. | mens |
> | Analog Innovations, Inc. | et |
> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
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