Re: [SI-LIST] : What speed scope should I consider?

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From: Adrian Shiner (adrian.shiner@virgin.net)
Date: Mon Nov 15 1999 - 13:20:08 PST


If there are 2 active (cmos) devices in a push pull (totem pole) output
stage then at some point both devices will be half way between on (low
impedance) and off (very high impedance). The impedance must vary during the
transition. Are you going to terminate both ends of the line which this
device is driving so that the impedance variation is minimised? Does it
matter? Perhaps we should return to current driven logic & stop worrying
about the voltages???

Adrian

----- Original Message -----
From: Chuck Hill <chuckh@altaeng.com>
To: <si-list@silab.eng.sun.com>; <si-list@silab.eng.sun.com>
Sent: 15 November 1999 02:38
Subject: RE: [SI-LIST] : What speed scope should I consider?

> Arpad,
>
> I have a proprietary method of measuring the transient impedance. My
> method is used to measure the output impedance of a buffer while switching
> between high and low states. My measurements show that the output
> impedance during buffer switching is often much higher than the on state
> resistance.
>
>
> Charles Hill, consultant
>
>
>
>
> At 04:47 PM 11/12/99 -0800, Muranyi, Arpad wrote:
> >I meant impedance vs. time, or non steady state but varying impedance,
> >such as the impedance of a buffer turning on/off vs. time.
> >
> >Arpad
>
>==========================================================================
> >
> >-----Original Message-----
> >From: Ron Miller [mailto:rmiller@Brocade.COM]
> >Sent: Friday, November 12, 1999 3:54 PM
> >To: si-list@silab.eng.sun.com
> >Subject: Re: [SI-LIST] : What speed scope should I consider?
> >
> >
> >Try Tektronix 11801 or a similar sampling scope from HP with the
> >TDR option.
> >
> >Ron Miller
> >
> >
> >"Muranyi, Arpad" wrote:
> >
> >
> >Does anyone know of any instrument that can measure transient impedance?
> >
> >Arpad Muranyi
> >Intel Corporation
> >========================================================================
> >
> >
> >Quote from previous correspondence:
> >
> >
> >"Network analyzers measure steady state impedance, not transient
impedance."
> >
> >
> >
> >**** To unsubscribe from si-list: send e-mail to
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****
> >
> >--
> >
> >Ronald B. Miller _\\|//_ Signal Integrity Engineer
> >
> >(408)487-8017 (' 0-0 ') fax(408)487-8017
> >
> > ==========0000-(_)0000===========
> >
> >Brocade Communications Systems, 1901 Guadalupe Parkway, San Jose, CA
95131
> >
> >rmiller@brocade.com, rbmiller@sjm.infi.net
> >
> >
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>
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