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Signal Chain Basics

Signal Chain Basics #115: The impact of the feedback resistance value on gain, bandwidth, and slew rate in current feedback amplifiers

Signal Chain Basics
Parreco
Parreco
12/15/2016 1:09:10 PM
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Newbie
Question about Ri
Z(s) is obviously a function of frequency.  (You.ve stated that it's fixed for a given amplifier, but I think you meant it's frequency response is fixed).  But my question is in regards to Ri....is Ri independent of frequency, or does that vary with frequency, as does Z(s)?

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Thomas7
Thomas7
10/27/2016 5:55:29 AM
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Re: Yuwegedusitesnaszemedia
Thank you, I've been seeking for info about this subject matter for ages and yours is the best I have discovered so far.

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Sergio Franco
Sergio Franco
8/24/2016 1:03:39 PM
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For a systematic analysis of the CFA....
...you may be interested in Sections 6.7 and 8.6 of the book "Design with Operational Amplifiers and Analog ICs", by Sergio Franco. ISBN 0-07-232084-2

 

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sroochi
sroochi
8/24/2016 9:05:49 AM
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Newbie
Re: Unclear article
It is my understanding that the effect of Zs is a function of α(s).  As I interpret the block diagram, an idea, infinitely widebandwidth buffer with infinite input impedance will let Z(s) go to ∞ so the equation (1) simplifies to the standard ideal op amp voltage follower equation. 

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pierree
pierree
8/21/2016 12:53:10 PM
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Re: Unclear article
the calculations do not necessarily give the result that we want, and indeed the term Z (s) is not defined.

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LorenDSiebert
LorenDSiebert
8/19/2016 2:12:19 PM
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Blogger
Re: Unclear article
Thanks for your feedback.  Z(s) is the open loop gain. Because it is defined by an input current and an output voltage it is a transimpedance gain.  It is fixed for a given amplifier.  

 

While Rg is also an external resistor once you select Rf the value of Rg is fixed for a given gain selection.  I could have been more clear.

 

I hope this response helps.

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sharps_eng
sharps_eng
8/19/2016 5:02:12 AM
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Newbie
Unclear article
The term Z(s) is mentioned but not defined.

The text states that only Rf is under the control of the user, but Rg is drawn as an external resistor. 

My immediate reaction was to stop reading the article. No logical framework for this device could be constructed in my head as I read on; so will this increase the number of people using these devices?

 

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