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Groups > sci.electronics.design > #518255 > unrolled thread
| Started by | John Larkin <jjlarkin@highland_snip_technology.com> |
|---|---|
| First post | 2018-10-03 15:03 -0700 |
| Last post | 2018-10-05 10:44 -0400 |
| Articles | 16 on this page of 96 — 26 participants |
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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
Page 5 of 5 — ← Prev page 1 2 3 4 [5]
| From | Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> |
|---|---|
| Date | 2018-10-06 14:45 -0400 |
| Message-ID | <ApmdnWelI5JdnyTGnZ2dnUU7-V3NnZ2d@supernews.com> |
| In reply to | #518493 |
On 10/5/18 9:36 PM, George Herold wrote: > On Friday, October 5, 2018 at 5:26:37 PM UTC-4, John Larkin wrote: >> On Fri, 5 Oct 2018 10:40:12 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 10/4/18 11:09 PM, Steve Wilson wrote: >>>> John Larkin <jjlarkin@highland_snip_technology.com> wrote: >>>> >>>>> On Thu, 4 Oct 2018 08:39:11 -0700 (PDT), Steve Wilson >>>>> <9fe142ac@gmail.com> wrote: >>>>>> I hope that anyone playing with 42GHz GBW would automatically add a base >>>>>> resistor to kill parasitic oscillations. Even a lowly 2N3904 can go into >>>>>> parasitics with a long base lead. >>>> >>>>> Or as an emitter follower with the base well bypassed to ground. The >>>>> wire bonds inside are nice high-Q inductors. >>>> >>>> How do you make an emitter follower when the base is bypassed to ground? >>>> Where do you put the signal? >>>> >>> >>> The classical example is the one-transistor !RESET generator, which is a >>> slow RC with an emitter follower. >> > It oscillates because of a slow edge and no hysteresis? If you put a resistor in series with the emitter, the reflected impedance at the base is a negative resistance. If that becomes larger than the extrinsic base resistance, the thing becomes unstable. The parasitic Ls and Cs help set the oscillation frequency, but even without them, the transistor becomes a relaxation oscillator. > Is it similar to cap. multiplier oscillations? > (do all single transistor circuits map onto each other?) It is precisely a cap multiplier. ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
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| From | George Herold <gherold@teachspin.com> |
|---|---|
| Date | 2018-10-06 12:46 -0700 |
| Message-ID | <b25be24a-3b15-455a-bb3a-c431f1232f48@googlegroups.com> |
| In reply to | #518558 |
On Saturday, October 6, 2018 at 2:45:29 PM UTC-4, Phil Hobbs wrote: > On 10/5/18 9:36 PM, George Herold wrote: > > On Friday, October 5, 2018 at 5:26:37 PM UTC-4, John Larkin wrote: > >> On Fri, 5 Oct 2018 10:40:12 -0400, Phil Hobbs > >> <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> > >>> On 10/4/18 11:09 PM, Steve Wilson wrote: > >>>> John Larkin <jjlarkin@highland_snip_technology.com> wrote: > >>>> > >>>>> On Thu, 4 Oct 2018 08:39:11 -0700 (PDT), Steve Wilson > >>>>> <9fe142ac@gmail.com> wrote: > >>>>>> I hope that anyone playing with 42GHz GBW would automatically add a base > >>>>>> resistor to kill parasitic oscillations. Even a lowly 2N3904 can go into > >>>>>> parasitics with a long base lead. > >>>> > >>>>> Or as an emitter follower with the base well bypassed to ground. The > >>>>> wire bonds inside are nice high-Q inductors. > >>>> > >>>> How do you make an emitter follower when the base is bypassed to ground? > >>>> Where do you put the signal? > >>>> > >>> > >>> The classical example is the one-transistor !RESET generator, which is a > >>> slow RC with an emitter follower. > >> > > It oscillates because of a slow edge and no hysteresis? > If you put a resistor in series with the emitter, the reflected > impedance at the base is a negative resistance. If that becomes larger > than the extrinsic base resistance, the thing becomes unstable. The > parasitic Ls and Cs help set the oscillation frequency, but even without > them, the transistor becomes a relaxation oscillator. > > > Is it similar to cap. multiplier oscillations? > > (do all single transistor circuits map onto each other?) > > It is precisely a cap multiplier. ;) Right. cap multiplier is a high-side emitter follower. Thanks, George H. > > Cheers > > Phil Hobbs > > -- > Dr Philip C D Hobbs > Principal Consultant > ElectroOptical Innovations LLC / Hobbs ElectroOptics > Optics, Electro-optics, Photonics, Analog Electronics > Briarcliff Manor NY 10510 > > http://electrooptical.net > http://hobbs-eo.com
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| From | John Larkin <jjlarkin@highlandtechnology.com> |
|---|---|
| Date | 2018-10-08 21:00 -0700 |
| Message-ID | <vb8ordth51oge27cjcdu0dtidte8qbkuje@4ax.com> |
| In reply to | #518558 |
On Sat, 6 Oct 2018 14:45:19 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >On 10/5/18 9:36 PM, George Herold wrote: >> On Friday, October 5, 2018 at 5:26:37 PM UTC-4, John Larkin wrote: >>> On Fri, 5 Oct 2018 10:40:12 -0400, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 10/4/18 11:09 PM, Steve Wilson wrote: >>>>> John Larkin <jjlarkin@highland_snip_technology.com> wrote: >>>>> >>>>>> On Thu, 4 Oct 2018 08:39:11 -0700 (PDT), Steve Wilson >>>>>> <9fe142ac@gmail.com> wrote: >>>>>>> I hope that anyone playing with 42GHz GBW would automatically add a base >>>>>>> resistor to kill parasitic oscillations. Even a lowly 2N3904 can go into >>>>>>> parasitics with a long base lead. >>>>> >>>>>> Or as an emitter follower with the base well bypassed to ground. The >>>>>> wire bonds inside are nice high-Q inductors. >>>>> >>>>> How do you make an emitter follower when the base is bypassed to ground? >>>>> Where do you put the signal? >>>>> >>>> >>>> The classical example is the one-transistor !RESET generator, which is a >>>> slow RC with an emitter follower. >>> >> It oscillates because of a slow edge and no hysteresis? >If you put a resistor in series with the emitter, the reflected >impedance at the base is a negative resistance. I don't understand that. At low frequencies, as the base voltage goes up, the base current goes up. The base looks ohmic. > If that becomes larger >than the extrinsic base resistance, the thing becomes unstable. The >parasitic Ls and Cs help set the oscillation frequency, but even without >them, the transistor becomes a relaxation oscillator. Can you Spice such a relaxation oscillator? At high frequencies, the base can look like a negative resistance; some oscillators work that way. -- John Larkin Highland Technology, Inc lunatic fringe electronics
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| From | Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> |
|---|---|
| Date | 2018-10-09 07:11 +0200 |
| Message-ID | <g22rjhFnledU1@mid.individual.net> |
| In reply to | #518781 |
Am 09.10.2018 um 06:00 schrieb John Larkin: > On Sat, 6 Oct 2018 14:45:19 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> If you put a resistor in series with the emitter, the reflected >> impedance at the base is a negative resistance. > > I don't understand that. At low frequencies, as the base voltage goes > up, the base current goes up. The base looks ohmic. That does not work at low frequencies. It takes takes transistor- internal parasitic capacitance to have an effect. The effect gets more pronounced for high emitter resistance and high emitter-GND capacitance. In the pages from Rhea that I have referenced, there is a transformation that converts such a loaded follower to the usual feedback loop by re-assigning GND to the emitter itself and redrawing the circuit. If you measure into base-gnd at RF, you see some pF in series with, say -50 Ohms. That is used in virtually all VHF/UHF VCOs from Z-Comm and others. I have once tried to pull down a Z-Comm VCXO by adding more varicaps since I had a few of them and needed lower frequencies. I didn't get very far because of the few pF that are in series to the base at RF. Disappointing, but finally understood. In the case of my baseband amplifier with the 2 IF3602 pairs, there are nF capacitances, and the amplifier goes negative impedance below 100 KHz. Ferrite chokes have quite a good Q at these frequencies, and one can tune the oscillation frequency with them :-( At higher frequencies where they work like resistors (as intended) they also generate voltage noise. You can't have your Kate, and Edith, too. regards, Gerhard
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| From | Chris Jones <lugnut808@spam.yahoo.com> |
|---|---|
| Date | 2018-10-09 23:20 +1100 |
| Message-ID | <x21vD.6457$vf.4197@fx05.am4> |
| In reply to | #518789 |
On 09/10/2018 16:11, Gerhard Hoffmann wrote: > Am 09.10.2018 um 06:00 schrieb John Larkin: >> On Sat, 6 Oct 2018 14:45:19 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> If you put a resistor in series with the emitter, the reflected >>> impedance at the base is a negative resistance. >> >> I don't understand that. At low frequencies, as the base voltage goes >> up, the base current goes up. The base looks ohmic. > > That does not work at low frequencies. It takes takes transistor- > internal parasitic capacitance to have an effect. The effect gets > more pronounced for high emitter resistance and high emitter-GND > capacitance. In the pages from Rhea that I have referenced, there is > a transformation that converts such a loaded follower to the usual > feedback loop by re-assigning GND to the emitter itself and redrawing > the circuit. > > If you measure into base-gnd at RF, you see some pF in series > with, say -50 Ohms. That is used in virtually all VHF/UHF > VCOs from Z-Comm and others. I have once tried to pull down > a Z-Comm VCXO by adding more varicaps since I had a few of them > and needed lower frequencies. I didn't get very far because of > the few pF that are in series to the base at RF. Disappointing, > but finally understood. > > In the case of my baseband amplifier with the 2 IF3602 pairs, > there are nF capacitances, and the amplifier goes negative > impedance below 100 KHz. Ferrite chokes have quite a good Q > at these frequencies, and one can tune the oscillation frequency > with them :-( > > At higher frequencies where they work like resistors (as intended) > they also generate voltage noise. You can't have your Kate, and > Edith, too. > > regards, > Gerhard > > I found that a unity gain buffer built from an AD8066 opamp also seems to have a negative resistance at its input. If you decide that you want to measure e.g. the DC offset, and short the input to ground with a 40cm jumper lead, it will oscillate at about 40MHz, and with shorter wires it will oscillate up to about 116MHz. Putting a 560R resistor in series with the input connector on the board, and a 3.3pF capacitor from the non-inverting input pin of the opamp to ground fixed it, but made it otherwise worse. I recall that there is nothing much in the datasheet to warn about this sort of problem.
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| From | Jeroen Belleman <jeroen@nospam.please> |
|---|---|
| Date | 2018-10-09 15:17 +0200 |
| Message-ID | <ppi9pg$12hj$1@gioia.aioe.org> |
| In reply to | #518812 |
Chris Jones wrote: > On 09/10/2018 16:11, Gerhard Hoffmann wrote: >> Am 09.10.2018 um 06:00 schrieb John Larkin: >>> On Sat, 6 Oct 2018 14:45:19 -0400, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> If you put a resistor in series with the emitter, the reflected >>>> impedance at the base is a negative resistance. >>> >>> I don't understand that. At low frequencies, as the base voltage goes >>> up, the base current goes up. The base looks ohmic. >> >> That does not work at low frequencies. It takes takes transistor- >> internal parasitic capacitance to have an effect. The effect gets >> more pronounced for high emitter resistance and high emitter-GND >> capacitance. In the pages from Rhea that I have referenced, there is >> a transformation that converts such a loaded follower to the usual >> feedback loop by re-assigning GND to the emitter itself and redrawing >> the circuit. >> >> If you measure into base-gnd at RF, you see some pF in series >> with, say -50 Ohms. That is used in virtually all VHF/UHF >> VCOs from Z-Comm and others. I have once tried to pull down >> a Z-Comm VCXO by adding more varicaps since I had a few of them >> and needed lower frequencies. I didn't get very far because of >> the few pF that are in series to the base at RF. Disappointing, >> but finally understood. >> >> In the case of my baseband amplifier with the 2 IF3602 pairs, >> there are nF capacitances, and the amplifier goes negative >> impedance below 100 KHz. Ferrite chokes have quite a good Q >> at these frequencies, and one can tune the oscillation frequency >> with them :-( >> >> At higher frequencies where they work like resistors (as intended) >> they also generate voltage noise. You can't have your Kate, and >> Edith, too. >> >> regards, >> Gerhard >> >> > > I found that a unity gain buffer built from an AD8066 opamp also seems > to have a negative resistance at its input. If you decide that you want > to measure e.g. the DC offset, and short the input to ground with a 40cm > jumper lead, it will oscillate at about 40MHz, and with shorter wires it > will oscillate up to about 116MHz. Putting a 560R resistor in series > with the input connector on the board, and a 3.3pF capacitor from the > non-inverting input pin of the opamp to ground fixed it, but made it > otherwise worse. I recall that there is nothing much in the datasheet to > warn about this sort of problem. > I use discrete amplifiers with feedback to set the input impedance to 50 Ohms, because that's quieter than using an actual terminating resistor. These also have a negative input impedance in a certain frequency range, which causes instability with reactive sources. Fortunately --well no, by design-- this happens outside of my signal bandwidth, so I can muffle that with some filtering at the input. Of course, like Gerhard says, the muffler produces thermal noise, but since that's outside my signal bandwidth, it doesn't matter. Jeroen Belleman
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| From | John Larkin <jjlarkin@highlandtechnology.com> |
|---|---|
| Date | 2018-10-04 09:18 -0700 |
| Message-ID | <k7fcrdhto66ek06h0g1t0939rhpt83ld0c@4ax.com> |
| In reply to | #518319 |
On Thu, 4 Oct 2018 05:00:24 -0700 (PDT), pcdhobbs@gmail.com wrote: >>>https://octopart.com/search?q=BFP650&oq=BFP650&start=0 > >>That would work, as a couple or few emitter followers to fan out my >>incoming signal. It has decent beta at, say, 50 mA or even 100 mA >>(driving something like 5 volts into 50 ohms). > >>The Vbe offset would be more predictable than the turn-on of a phemt. > >Their low drain impedances make pHEMTs very disappointing as followers, unless you bootstrap the drain. The late lamented ATF38148 could have a gain of 0.5 as a follower. > >>I'll be timing edges to picoseconds so I don't want unpredictable >offsets. > >You'll need a base resistor to keep it from oscillating. Don't let anybody hang a cable on it. > >Cheers > >Phil Hobbs Looks like the best, fastest, lowest delay, lowest delay TC, and lowest jitter digital logic buffer will be an opamp! -- John Larkin Highland Technology, Inc lunatic fringe electronics
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| From | Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> |
|---|---|
| Date | 2018-10-04 12:39 -0400 |
| Message-ID | <gZSdndNi0eDf3yvGnZ2dnUU7-SmdnZ2d@supernews.com> |
| In reply to | #518337 |
On 10/4/18 12:18 PM, John Larkin wrote: > On Thu, 4 Oct 2018 05:00:24 -0700 (PDT), pcdhobbs@gmail.com wrote: > >>>> https://octopart.com/search?q=BFP650&oq=BFP650&start=0 >> >>> That would work, as a couple or few emitter followers to fan out my >>> incoming signal. It has decent beta at, say, 50 mA or even 100 mA >>> (driving something like 5 volts into 50 ohms). >> >>> The Vbe offset would be more predictable than the turn-on of a phemt. >> >> Their low drain impedances make pHEMTs very disappointing as followers, unless you bootstrap the drain. The late lamented ATF38148 could have a gain of 0.5 as a follower. >> >>> I'll be timing edges to picoseconds so I don't want unpredictable >> offsets. >> >> You'll need a base resistor to keep it from oscillating. Don't let anybody hang a cable on it. >> >> Cheers >> >> Phil Hobbs > > Looks like the best, fastest, lowest delay, lowest delay TC, and > lowest jitter digital logic buffer will be an opamp! > > Lowest power and lowest cost too? ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
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| From | John Larkin <jjlarkin@highland_snip_technology.com> |
|---|---|
| Date | 2018-10-04 11:51 -0700 |
| Message-ID | <28ocrdhtdq5su3pqggoh9v5886f2l968ki@4ax.com> |
| In reply to | #518341 |
On Thu, 4 Oct 2018 12:39:29 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote: >On 10/4/18 12:18 PM, John Larkin wrote: >> On Thu, 4 Oct 2018 05:00:24 -0700 (PDT), pcdhobbs@gmail.com wrote: >> >>>>> https://octopart.com/search?q=BFP650&oq=BFP650&start=0 >>> >>>> That would work, as a couple or few emitter followers to fan out my >>>> incoming signal. It has decent beta at, say, 50 mA or even 100 mA >>>> (driving something like 5 volts into 50 ohms). >>> >>>> The Vbe offset would be more predictable than the turn-on of a phemt. >>> >>> Their low drain impedances make pHEMTs very disappointing as followers, unless you bootstrap the drain. The late lamented ATF38148 could have a gain of 0.5 as a follower. >>> >>>> I'll be timing edges to picoseconds so I don't want unpredictable >>> offsets. >>> >>> You'll need a base resistor to keep it from oscillating. Don't let anybody hang a cable on it. >>> >>> Cheers >>> >>> Phil Hobbs >> >> Looks like the best, fastest, lowest delay, lowest delay TC, and >> lowest jitter digital logic buffer will be an opamp! >> >> >Lowest power and lowest cost too? ;) I'm building a test set (for an astronomical heap of dollars) so that doesn't matter. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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| From | Piotr Wyderski <peter.pan@neverland.mil> |
|---|---|
| Date | 2018-10-08 13:19 +0200 |
| Message-ID | <ppfef7$g99$1@node2.news.atman.pl> |
| In reply to | #518299 |
John Larkin wrote: > I'll be timing edges to picoseconds so I don't want unpredictable > offsets. Given that a picosecond is just enough to travel 0.3mm at light speed in vacuum, maybe 0.2mm on FR4, how are you going to check if all the timings and delays are correct? Best regards, Piotr
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| From | John Larkin <jjlarkin@highlandtechnology.com> |
|---|---|
| Date | 2018-10-08 08:52 -0700 |
| Message-ID | <l4rmrddem0p5ahn71peingjlvbjq29b0jf@4ax.com> |
| In reply to | #518706 |
On Mon, 8 Oct 2018 13:19:01 +0200, Piotr Wyderski <peter.pan@neverland.mil> wrote: >John Larkin wrote: > >> I'll be timing edges to picoseconds so I don't want unpredictable >> offsets. > >Given that a picosecond is just enough to travel 0.3mm at light speed >in vacuum, maybe 0.2mm on FR4, how are you going to check if all the >timings and delays are correct? > > Best regards, Piotr There might be some mild hand-waving involved. The customer's machine has, in some boxes, microsecond delays that drift around, and maybe a nanosecond or two of of jitter, and all sorts electrical and optical propagation delays, and they want 1 ps jitter and 100 ps accuracy. That's meaningless, but I need to keep them happy. I can use an 11801 sampling probe and poke around, and make a list of time fudge factors, to make up for cable and pcb and part delays. That can go into a cal table for the test set. Once that's done, I need stability. CMOS gates typically drift positive a couple ps per degree C. That BUF602 will help at least to get the fudge factors measured before everything drifts too far. Buffering and fanning out the fast signals allows better PCB geometry. -- John Larkin Highland Technology, Inc lunatic fringe electronics
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| From | whit3rd <whit3rd@gmail.com> |
|---|---|
| Date | 2018-10-04 11:57 -0700 |
| Message-ID | <6080ab6e-8899-4c4b-9c8b-3adaeca9f3d3@googlegroups.com> |
| In reply to | #518255 |
On Wednesday, October 3, 2018 at 3:03:49 PM UTC-7, John Larkin wrote: > I'm designing a test board for a laser controller. Incoming signals, > fast 5 volt pulses, will need to get routed... I could fan out some of the signals > at their input connector. I want a zero-delay, zero-jitter buffer. > Under 1 ns delay might be a reasonable target, with very stable prop > delay. How about SN65LVDS20? The 'enable' input can solve some of the switching issues. Differential gives you both polarities... ECL is good, too, because the slew rate of your input pulse will be high when passing the threshold (and any ECL gate has a bit of voltage gain anyhow, so output slew rate will be healthy). MC10H104 would be another candidate, and comes with a lovely opportunity to pay a Trump-era tariff, according to DigiKey.
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| From | David Nadlinger <david@klickverbot.at> |
|---|---|
| Date | 2018-10-04 23:05 +0100 |
| Message-ID | <pp62qv$92n$1@news.ox.ac.uk> |
| In reply to | #518255 |
On 03.10.18 11:03 PM, John Larkin wrote: > Just resistors could work, but that loses amplitude, and the ends of > the fanout traces would have to be always terminated to avoid > reflections. Something unilateral would be easier. This doesn't exactly fit the "single-ended, easy termination" bill, but I've recently had some fun (and success) with the ADCLK950: http://www.analog.com/media/en/technical-documentation/data-sheet/ADCLK950.pdf 2 inputs, 10 outputs, propagation delay ~210 ps, 75 fs rms jitter. How stable do you need the propagation delay to be? — David
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| From | John Larkin <jjlarkin@highland_snip_technology.com> |
|---|---|
| Date | 2018-10-04 17:23 -0700 |
| Message-ID | <11bdrdlor3mq7sfgkaoovifrudjm64m93h@4ax.com> |
| In reply to | #518369 |
On Thu, 4 Oct 2018 23:05:20 +0100, David Nadlinger <david@klickverbot.at> wrote: >On 03.10.18 11:03 PM, John Larkin wrote: >> Just resistors could work, but that loses amplitude, and the ends of >> the fanout traces would have to be always terminated to avoid >> reflections. Something unilateral would be easier. > >This doesn't exactly fit the "single-ended, easy termination" bill, but >I've recently had some fun (and success) with the ADCLK950: > >http://www.analog.com/media/en/technical-documentation/data-sheet/ADCLK950.pdf > >2 inputs, 10 outputs, propagation delay ~210 ps, 75 fs rms jitter. Nice, but it's all low-voltage differential. I need 5 volt swings in and out. > >How stable do you need the propagation delay to be? My DUT will be spec'd to 1 ns accuracy (well, the customer wants 200 ps, but that's silly) and maybe 30 ps RMS jitter. We'll have to occasionally characterize all the component and traces and cable delays in the test set, and fudge them out of the tests. Gigantic pain. After that, we'd like things to be stable to maybe 100 ps. I guess I should put an RTD or an LM35 on the test board, so my interfaced DVM can measure board temperature. I sure hope we'd never need to actually use that. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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| From | Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> |
|---|---|
| Date | 2018-10-05 11:26 +0200 |
| Message-ID | <g1op1aFlpdqU1@mid.individual.net> |
| In reply to | #518385 |
Am 05.10.2018 um 02:23 schrieb John Larkin: > On Thu, 4 Oct 2018 23:05:20 +0100, David Nadlinger > Nice, but it's all low-voltage differential. I need 5 volt swings in > and out. A real pain. And the receiver inputs after that will probably switch at 1.6V. > >> >> How stable do you need the propagation delay to be? > > My DUT will be spec'd to 1 ns accuracy (well, the customer wants 200 > ps, but that's silly) and maybe 30 ps RMS jitter. We'll have to > occasionally characterize all the component and traces and cable > delays in the test set, and fudge them out of the tests. Gigantic > pain. After that, we'd like things to be stable to maybe 100 ps. A customer of mine measured their cables in the temp chamber. That was real "fun". It is well-known that PTFE has a crystallization change at 23°C, where it hurts most, esp. when most quality cables are PTFE. If you want stable delays, it's probably best to try to be as fast as possible and then limit the BW with film R and NP0 C to sane values. Excess BW brings excess noise, brings excess jitter. Distributing a sine wave + a qualifier for the zero crossings takes cable dispersion out of the equation. One gains precisely located points in time but loses arbitrary edge position. regards, Gerhard
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| From | Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> |
|---|---|
| Date | 2018-10-05 10:44 -0400 |
| Message-ID | <IIydnXYebLYh5SrGnZ2dnUU7-bvNnZ2d@supernews.com> |
| In reply to | #518409 |
On 10/5/18 5:26 AM, Gerhard Hoffmann wrote: > Am 05.10.2018 um 02:23 schrieb John Larkin: >> On Thu, 4 Oct 2018 23:05:20 +0100, David Nadlinger > >> Nice, but it's all low-voltage differential. I need 5 volt swings in >> and out. > > A real pain. And the receiver inputs after that will probably switch at > 1.6V. > >> >>> >>> How stable do you need the propagation delay to be? >> >> My DUT will be spec'd to 1 ns accuracy (well, the customer wants 200 >> ps, but that's silly) and maybe 30 ps RMS jitter. We'll have to >> occasionally characterize all the component and traces and cable >> delays in the test set, and fudge them out of the tests. Gigantic >> pain. After that, we'd like things to be stable to maybe 100 ps. > > A customer of mine measured their cables in the temp chamber. > That was real "fun". > It is well-known that PTFE has a crystallization change at 23°C, > where it hurts most, esp. when most quality cables are PTFE. Yup. TC of epsilon is about 2000 ppm/K in the glass transition region iirc. Polyethylene is much better. > > If you want stable delays, it's probably best to try to be as > fast as possible and then limit the BW with film R and NP0 C > to sane values. Excess BW brings excess noise, brings excess jitter. > > Distributing a sine wave + a qualifier for the zero crossings > takes cable dispersion out of the equation. One gains precisely > located points in time but loses arbitrary edge position. Interesting idea. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
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