Groups > sci.electronics.design > #518569

Re: really fast buffers

Newsgroups	sci.electronics.design
Subject	Re: really fast buffers
From	Steve Wilson <no@spam.com>
References	(8 earlier) <rYSdncl0g5hM6irGnZ2dnUU7-TWdnZ2d@supernews.com> <u8lfrdtffa2gqdvep73d514gd2qgp4q7j8@4ax.com> <787c7a2b-c1a9-4330-830b-8ab9a58d30d0@googlegroups.com> <XnsA972E4A74F46Cidtokenpost@69.16.179.22> <ApmdnWalI5KUniTGnZ2dnUU7-V2dnZ2d@supernews.com>
Message-ID	<XnsA9739931E279Aidtokenpost@69.16.179.22> (permalink)
Organization	http://www.NewsDemon.com
Date	2018-10-06 19:03 +0000

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Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

> On 10/5/18 10:28 PM, Steve Wilson wrote:
>> George Herold <gherold@teachspin.com> wrote:

>>> It oscillates because of a slow edge and no hysteresis?

>> It oscillates because of inductance in the base lead. Along with the
>> base- emitter capacitance and capacitance from the emitter to ground,
>> this forms a Colpitts oscillator, which is one of the most vigorous
>> oscillators known. It can accept an extremely wide range of parameters
>> and still oscillate. 

>> The purpose of the resistor in the base lead is to dampen the Q of the
>> tank so oscillations are no longer possible.

>>> Is it similar to cap. multiplier oscillations?

>> Could be. Any place where you have some inductance in the base and
>> capacitance from the emitter to ground could form a Colpitts,
>> especially where you have some inductance in the emitter lead. 

> The key ingredient is negative input resistance.

That term always bothered me. Negative input resistance to what? If you 
look a the base input impedance, it is always positive. When the 
oscillations get going, the transistor is cut off most of the time. Where 
is the negative input impedance then?

The key ingredient is positive feedback. Say the emitter generates a 
voltage that is fed into the tank. The capacitive divider generates a 
voltage on the base that is higher than the emitter. The emitter follower 
operation means the voltage fed to the capacitive divider is larger than 
the original. Positive feedback. Oscillations ensue.

> Cheers

> Phil Hobbs

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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