Re: [SI-LIST] : ESR and bypass caps

About this list Date view Thread view Subject view Author view

From: Douglas C. Smith (doug@dsmith.org)
Date: Fri Feb 04 2000 - 18:45:48 PST


Hi All,

Last week I put up on my website at www.emcesd.com (or www.dsmith.org)
this month's Technical Tidbit article on measuring capacitor
parasitics very simply using a scope, logic pulse generator, and a 50
Ohm resistor. The data for the article was taken about 15 years ago
using an analog scope. I dug up the data as it seemed to bear on
recent (and continuing) discussions on capacitors.

Doug

Doug Brooks wrote:
>
> Hi all,
>
> We have been putting some thought into this question and have derived,
> definitively we believe, some "truths" about this topic. They are
> summarized below. The first two or three are apparent and not really news,
> although we "prove" it from the normal formulas. The fourth has been
> verified as a "truth". We have presented all this in an article "ESR and
> Bypass Capacitor Self Resonant Behavior: How to Select Bypass Caps. We
> invite you to review the article.
>
> 1. As ESR goes down, the troughs get deeper and the peaks get higher!
> 2. The minimum impedance value is NOT NECESSARILY ESR (or ESR/n); it can
> and is lower than that!
> 3. The minimum impedance points are not necessarily at the capacitor
> self-resonant points.
> 4. For a given number of capacitors, better results can be obtained from
> more capacitor values, with moderate ESRs, spread over a range than with a
> smaller set of capacitor VALUES, with very low ESRs, even at well chosen
> specific self resonant frequencies.
>
> In order to verify the theory, we had to write a program that could, for
> any arbitrary set of capacitor (and inductance and ESR) values, find the
> minimum and maximum frequencies and impedance values. We have done that.
> The calculator is available for license.
>
> The article can be obtained from our web site:
>
> http://www.ultracad.com
>
> Follow the links to the ESR article.
>
> Doug Brooks
> UltraCAD
>
> .
> ************************************************************
> See our updated message re in-house seminars on our web page
> .
> Doug Brooks, President doug@eskimo.com
> UltraCAD Design, Inc. http://www.ultracad.com
>
> **** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu
> ****

-- 
-----------------------------------------------------------
    ___          _           Doug Smith
     \          / )          P.O. Box 1457
      =========              Los Gatos, CA 95031-1457
   _ / \     / \ _           TEL/FAX: 408-356-4186/358-3799
 /  /\  \ ] /  /\  \         Mobile:  408-858-4528
|  q-----( )  |  o  |        Email:   doug@dsmith.org
 \ _ /    ]    \ _ /         Website: http://www.dsmith.org
-----------------------------------------------------------

**** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu ****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Apr 20 2000 - 11:34:59 PDT