Groups > sci.electronics.design > #518621

Re: really fast buffers

From	<698839253X6D445TD@nospam.org>
Newsgroups	sci.electronics.design
Subject	Re: really fast buffers
Date	2018-10-07 07:15 +0000
Organization	Aioe.org NNTP Server
Message-ID	<ppcbro$vq1$1@gioia.aioe.org> (permalink)
References	(11 earlier) <XnsA972E4A74F46Cidtokenpost@69.16.179.22> <ApmdnWalI5KUniTGnZ2dnUU7-V2dnZ2d@supernews.com> <XnsA9739931E279Aidtokenpost@69.16.179.22> <g1sjm5Ffa4qU1@mid.individual.net> <XnsA973AD4CC2A18idtokenpost@69.16.179.23>

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Steve Wilson
>Another example is a simple 74HC04 Pierce oscillator with an LC tank as 
>feedback.
>
>The input impedance of the 74HC04 is capacitive. The impedance is
>
>Xc = 1 / (2piFC)
>
>There is no negative input resistance.
>
>A further example is "A General Theory of Phase Noise in Electrical 
>Oscillators,  by Ali Hajimiri, Student Member, IEEE, and Thomas H. Lee, 
>Member, IEEE"
>
>https://authors.library.caltech.edu/4917/1/HAJieeejssc98.pdf
>
>"Consider as one example the Colpitts oscillator of Fig. 5(a).
>The collector voltage and the collector current of the transistor
>are shown in Fig. 13. Note that the collector current consists
>of a short period of large current followed by a quiet interval.
>The surge of current occurs at the minimum of the voltage
>across the tank where the ISF is small."
>
>Clearly the collector current is a function of the base current, and is in 
>phase with the base current. The input impedance at the base is positive, 
>therefore there is no negative resistance term available.
>
>Oscillators work on positive feedback. If the loop gain is positive and in 
>phase, oscillations ensue.

Steve I completely agree with your viewpoint.
Just saying 'input has negative impedance' does not explain a thing,
and then adding a resistor to make it positive again is fake close to string theory.
Better is to understand the Cbe - CeGND step up, and that can be compensated for in many ways
and is of no significance when driving the base with some circuits.

I have had exactly one case of an oscillating emitter follower in my life,
and that was in a missile tracking system,
replacing the transistor fixed it, not all trannies are the same ... 

I do not use base resistors in my RF amps, that just decreases performance.
And no those do not oscillate.

You oscillators are doing something basically wrong, layout?

;-)

hehe
;-)

Thread

really fast buffers John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-03 15:03 -0700
  Re: really fast buffers Lasse Langwadt Christensen <langwadt@fonz.dk> - 2018-10-03 15:23 -0700
    Re: really fast buffers Andy Bennet <andyb@andy.com> - 2018-10-04 08:20 +0100
      Re: really fast buffers Lasse Langwadt Christensen <langwadt@fonz.dk> - 2018-10-04 08:45 -0700
  Re: really fast buffers John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-03 15:52 -0700
    Re: really fast buffers George Herold <gherold@teachspin.com> - 2018-10-03 18:08 -0700
      Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-03 20:02 -0700
  Re: really fast buffers bitrex <user@example.net> - 2018-10-03 21:54 -0400
    Re: really fast buffers Steve Wilson <9fe142ac@gmail.com> - 2018-10-03 20:10 -0700
      Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-03 20:40 -0700
        Re: really fast buffers pcdhobbs@gmail.com - 2018-10-04 05:00 -0700
          Re: really fast buffers Steve Wilson <9fe142ac@gmail.com> - 2018-10-04 08:39 -0700
            Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-04 12:38 -0400
              Re: really fast buffers Steve Wilson <9fe142ac@gmail.com> - 2018-10-04 14:35 -0700
                Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-04 18:27 -0400
                Re: really fast buffers Steve Wilson <no@spam.com> - 2018-10-05 03:21 +0000
                Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-05 10:38 -0400
            Re: really fast buffers John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-04 11:50 -0700
              Re: really fast buffers Clifford Heath <no.spam@please.net> - 2018-10-05 09:26 +1000
                Re: really fast buffers John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-04 17:09 -0700
                Re: really fast buffers Steve Wilson <no@spam.com> - 2018-10-05 03:12 +0000
                Re: really fast buffers John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-05 14:18 -0700
                Re: really fast buffers Steve Wilson <no@spam.com> - 2018-10-05 23:42 +0000
                Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-06 14:41 -0400
              Re: really fast buffers Steve Wilson <no@spam.com> - 2018-10-05 03:09 +0000
                Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-05 10:40 -0400
                Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-05 11:06 -0400
                Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-05 19:16 -0700
                Re: really fast buffers John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-05 14:26 -0700
                Re: really fast buffers George Herold <gherold@teachspin.com> - 2018-10-05 18:36 -0700
                Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-05 19:22 -0700
                Re: really fast buffers Steve Wilson <no@spam.com> - 2018-10-06 02:28 +0000
                Re: really fast buffers <698839253X6D445TD@nospam.org> - 2018-10-06 06:03 +0000
                Re: really fast buffers Steve Wilson <9fe142ac@gmail.com> - 2018-10-05 23:41 -0700
                Re: really fast buffers <698839253X6D445TD@nospam.org> - 2018-10-06 08:12 +0000
                Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-06 14:46 -0400
                Re: really fast buffers Steve Wilson <no@spam.com> - 2018-10-06 19:03 +0000
                Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-06 15:32 -0400
                Re: really fast buffers Steve Wilson <no@spam.com> - 2018-10-06 20:08 +0000
                Re: really fast buffers Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-06 22:19 +0200
                Re: really fast buffers Steve Wilson <no@spam.com> - 2018-10-06 21:02 +0000
                Re: really fast buffers tabbypurr@gmail.com - 2018-10-06 16:57 -0700
                Re: really fast buffers krw@notreal.com - 2018-10-06 22:30 -0400
                Re: really fast buffers Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-07 04:30 +0200
                Re: really fast buffers <698839253X6D445TD@nospam.org> - 2018-10-07 07:15 +0000
                Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-07 08:24 -0700
                Re: really fast buffers bill.sloman@ieee.org - 2018-10-07 18:51 -0700
                Re: really fast buffers tabbypurr@gmail.com - 2018-10-08 08:16 -0700
                Re: really fast buffers Winfield Hill <hill@rowland.harvard.edu> - 2018-10-07 07:19 -0700
                Re: really fast buffers Robert Baer <robertbaer@localnet.com> - 2018-10-10 00:38 -0700
                Re: really fast buffers tabbypurr@gmail.com - 2018-10-10 03:02 -0700
                Re: really fast buffers bill.sloman@ieee.org - 2018-10-10 04:07 -0700
                Re: really fast buffers DecadentLinuxUserNumeroUno@decadence.org - 2018-10-10 11:28 +0000
                Re: really fast buffers Robert Baer <robertbaer@localnet.com> - 2018-10-11 22:06 -0700
                Re: really fast buffers bill.sloman@ieee.org - 2018-10-12 00:08 -0700
                Re: really fast buffers Robert Baer <robertbaer@localnet.com> - 2018-10-13 22:29 -0700
                Re: really fast buffers bill.sloman@ieee.org - 2018-10-14 00:30 -0700
                Re: really fast buffers Robert Baer <robertbaer@localnet.com> - 2018-10-15 19:38 -0700
                Re: really fast buffers bill.sloman@ieee.org - 2018-10-15 20:55 -0700
                Re: really fast buffers tabbypurr@gmail.com - 2018-10-14 04:31 -0700
                Re: really fast buffers bill.sloman@ieee.org - 2018-10-14 07:29 -0700
                Re: really fast buffers Robert Baer <robertbaer@localnet.com> - 2018-10-15 19:42 -0700
                Re: really fast buffers bill.sloman@ieee.org - 2018-10-15 20:57 -0700
                Re: really fast buffers tabbypurr@gmail.com - 2018-10-16 08:41 -0700
                Re: really fast buffers krw@notreal.com - 2018-10-16 17:38 -0400
                Re: really fast buffers bill.sloman@ieee.org - 2018-10-16 19:37 -0700
                Re: really fast buffers bill.sloman@ieee.org - 2018-10-16 19:40 -0700
                Re: really fast buffers Robert Baer <robertbaer@localnet.com> - 2018-10-15 19:40 -0700
                Re: really fast buffers Robert Baer <robertbaer@localnet.com> - 2018-10-11 22:04 -0700
                Re: really fast buffers tabbypurr@gmail.com - 2018-10-12 08:02 -0700
                Re: really fast buffers Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-10 14:06 +0200
                Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-10 08:31 -0700
                Re: really fast buffers Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-11 01:49 +0200
                Re: really fast buffers John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-10 17:41 -0700
                Re: really fast buffers "John Miles, KE5FX" <jmiles@gmail.com> - 2018-10-10 20:53 -0700
                Re: really fast buffers Jasen Betts <jasen@xnet.co.nz> - 2018-10-11 05:47 +0000
                Re: really fast buffers Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-11 12:35 +0200
                Re: really fast buffers George Herold <gherold@teachspin.com> - 2018-10-06 12:39 -0700
                Re: really fast buffers Steve Wilson <no@spam.com> - 2018-10-06 20:11 +0000
                Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-08 20:26 -0700
                Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-06 14:45 -0400
                Re: really fast buffers George Herold <gherold@teachspin.com> - 2018-10-06 12:46 -0700
                Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-08 21:00 -0700
                Re: really fast buffers Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-09 07:11 +0200
                Re: really fast buffers Chris Jones <lugnut808@spam.yahoo.com> - 2018-10-09 23:20 +1100
                Re: really fast buffers Jeroen Belleman <jeroen@nospam.please> - 2018-10-09 15:17 +0200
          Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-04 09:18 -0700
            Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-04 12:39 -0400
              Re: really fast buffers John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-04 11:51 -0700
        Re: really fast buffers Piotr Wyderski <peter.pan@neverland.mil> - 2018-10-08 13:19 +0200
          Re: really fast buffers John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-08 08:52 -0700
  Re: really fast buffers whit3rd <whit3rd@gmail.com> - 2018-10-04 11:57 -0700
  Re: really fast buffers David Nadlinger <david@klickverbot.at> - 2018-10-04 23:05 +0100
    Re: really fast buffers John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-04 17:23 -0700
      Re: really fast buffers Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-05 11:26 +0200
        Re: really fast buffers Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2018-10-05 10:44 -0400

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