On 12/16/2015 07:42 PM, John Larkin wrote:> On Thu, 17 Dec 2015 10:46:41 +1100, Clifford Heath > <no.spam@please.net> wrote: > >> On 17/12/15 09:22, Phil Hobbs wrote: >>> On 12/16/2015 01:16 PM, Phil Hobbs wrote: >>>> On 12/16/2015 01:08 PM, Phil Hobbs wrote: >>>>> On 12/16/2015 12:30 PM, John Larkin wrote: >>>>>> On Wed, 16 Dec 2015 10:19:08 -0500, Phil Hobbs >>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>> >>>>>>> On 12/16/2015 04:06 AM, piglet wrote: >>>>>>>> On 15/12/2015 16:30, Phil Hobbs wrote: >>>>>>>>>> Cute. I might be more inclined to turn the ALC transistor >>>>>>>>>> upside down >>>>>>>>>> and use a PNP. That would avoid loading the emitter of the >>>>>>>>>> oscillator >>>>>>>>>> transistor. >>>>>>>>> >>>>>>>>> Come to think about it, by omitting the diode and cap, connecting >>>>>>>>> the >>>>>>>>> PNP's base to the NPN's collector, and putting a bit of positive >>>>>>>>> bias >>>>>>>>> on the PNP's emitter, it could kill the NPN's collector current >>>>>>>>> before >>>>>>>>> saturation occurs. That wouldn't have any slow bias TCs. >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> >>>>>>>>> Phil Hobbs >>>>>>>>> >>>>>>>> >>>>>>>> That is a very neat idea, true cycle by cycle control, the tank Q >>>>>>>> will >>>>>>>> clean up the even harmonic distortion. >>>>>>>> >>>>>>>> piglet >>>>>>>> >>>>>>> >>>>>>> Seems to work all right, though there's some loading from the PNP's >>>>>>> base, which seems to be mostly capacitive. >>>>>> >>>>>> That seems to me to be about equivalent to diode clipping the tank to >>>>>> limit amplitude, or at least diode clipping with a bit of added series >>>>>> resistance to soften things up. >>>>> >>>>> I don't think so, on account of the beta of the PNP, which reduces the >>>>> tank loading (which is more or less the point of the exercise). At >>>>> those sorts of speeds, it's probably possible to use a PNP Darlington. >>>>> >>>>> The gain-limiting current is still >>>>>> mostly short, peak-of-sine spikes. They are applied to the capacitor >>>>>> tap, not to the top of the tank, but then are correspondingly bigger. >>>>>> >>>>>> A slow AGC would gradually reduce the loop gain, but that would be, >>>>>> well, slow. Any fast AGC must look ohmic to the tank and thus kill Q. >>>>> >>>>> If the PNP's beta and Early voltage were infinite, it would look exactly >>>>> like switching the NPN's emitter current on and off. No tank loading at >>>>> all. >>>>> >>>>>> >>>>>> Here's an oscillator with diode+resistor clipping. The capacitor ratio >>>>>> is extreme, 24:1, which in unconventional but makes the NPN run fairly >>>>>> linear. >>>>>> >>>>>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/JL_LC_1.zip >>>>>> >>>>> >>>>> You're pulling a big spike out of the top of the tank, though--put >>>>> another of those 1m resistors between the tank and the collector, and >>>>> you'll see. My PNP pulls almost all capacitive current out of the top >>>>> of the tank, and there aren't any spikes there. >>>>> >>>>>> >>>>>> I guess the ideal circuit would use hard clipping at first and >>>>>> gracefully transition to a slow leveling loop. The PNP sort of does >>>>>> that, but its current is still spikey. If you don't mind the amplitude >>>>>> changing 10 or 20% before it stabilizes, just a slowish loop would be >>>>>> OK, and Q would benefit. >>>>>> >>>>> >>>>> On the other hand, just rebiasing it so that it current limits instead >>>>> of voltage limiting will increase the loaded Q by a large factor. A >>>>> resistor between the emitter and the tank helps too. (Small capacitors >>>>> also work.) >>>>> >>>>> For instance, your circuit (280 uA quiescent bias) gets a peak inductor >>>>> current of 8 mA, whereas the one below (72 uA quiescent bias) peaks at >>>>> 60 mA. So that's a factor of 30 reduction in loading, with a >>>>> corresponding increase in loaded Q. >>>>> >>>>>> My circuit has the charm of simplicity, and settles fast, and may be >>>>>> good enough for what I want to do. The overall PLL takes over after a >>>>>> while, so extreme Q isn't really needed. >>>>> >>>>> Well, the higher the Q, the less vulnerable the resonator is to external >>>>> effects. That has a direct impact on the jitter. >>>> >>>> Belay that. It's much better, but it still voltage-limits. Revised >>>> version coming soon to a simulator near you. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>>> >>>> >>> Okay, it's fixed. This one works essentially the same over a 6:1 range >>> of Q_L (100 to 600 milliohms out of 60-odd ohms). With < 50 uA >>> quiescent bias, it has circulating currents of 8-10 mA in the tank, and >>> amplitude limiting is controlled by the transconductance of the NPN. >> >> Thanks. >> >> The initial amplitude is dependent on the 220R. What else does it depend >> on? May need to make that a trimpot. > > Whenever I mention "trimpot" the kids here start calling assisted-care > retirement facilities to ship me off to. > > My only objection to a trimpot here is, how would you set it? You can > hardly probe the tank without upsetting it.I don't think there's a need, if the comparator threshold is near ground. Amplitude is a second-order effect then. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
inductor tempco
Started by ●December 13, 2015
Reply by ●December 16, 20152015-12-16
Reply by ●December 16, 20152015-12-16
On Wed, 16 Dec 2015 19:56:59 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 12/16/2015 07:42 PM, John Larkin wrote: >> On Thu, 17 Dec 2015 10:46:41 +1100, Clifford Heath >> <no.spam@please.net> wrote: >> >>> On 17/12/15 09:22, Phil Hobbs wrote: >>>> On 12/16/2015 01:16 PM, Phil Hobbs wrote: >>>>> On 12/16/2015 01:08 PM, Phil Hobbs wrote: >>>>>> On 12/16/2015 12:30 PM, John Larkin wrote: >>>>>>> On Wed, 16 Dec 2015 10:19:08 -0500, Phil Hobbs >>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>> >>>>>>>> On 12/16/2015 04:06 AM, piglet wrote: >>>>>>>>> On 15/12/2015 16:30, Phil Hobbs wrote: >>>>>>>>>>> Cute. I might be more inclined to turn the ALC transistor >>>>>>>>>>> upside down >>>>>>>>>>> and use a PNP. That would avoid loading the emitter of the >>>>>>>>>>> oscillator >>>>>>>>>>> transistor. >>>>>>>>>> >>>>>>>>>> Come to think about it, by omitting the diode and cap, connecting >>>>>>>>>> the >>>>>>>>>> PNP's base to the NPN's collector, and putting a bit of positive >>>>>>>>>> bias >>>>>>>>>> on the PNP's emitter, it could kill the NPN's collector current >>>>>>>>>> before >>>>>>>>>> saturation occurs. That wouldn't have any slow bias TCs. >>>>>>>>>> >>>>>>>>>> Cheers >>>>>>>>>> >>>>>>>>>> Phil Hobbs >>>>>>>>>> >>>>>>>>> >>>>>>>>> That is a very neat idea, true cycle by cycle control, the tank Q >>>>>>>>> will >>>>>>>>> clean up the even harmonic distortion. >>>>>>>>> >>>>>>>>> piglet >>>>>>>>> >>>>>>>> >>>>>>>> Seems to work all right, though there's some loading from the PNP's >>>>>>>> base, which seems to be mostly capacitive. >>>>>>> >>>>>>> That seems to me to be about equivalent to diode clipping the tank to >>>>>>> limit amplitude, or at least diode clipping with a bit of added series >>>>>>> resistance to soften things up. >>>>>> >>>>>> I don't think so, on account of the beta of the PNP, which reduces the >>>>>> tank loading (which is more or less the point of the exercise). At >>>>>> those sorts of speeds, it's probably possible to use a PNP Darlington. >>>>>> >>>>>> The gain-limiting current is still >>>>>>> mostly short, peak-of-sine spikes. They are applied to the capacitor >>>>>>> tap, not to the top of the tank, but then are correspondingly bigger. >>>>>>> >>>>>>> A slow AGC would gradually reduce the loop gain, but that would be, >>>>>>> well, slow. Any fast AGC must look ohmic to the tank and thus kill Q. >>>>>> >>>>>> If the PNP's beta and Early voltage were infinite, it would look exactly >>>>>> like switching the NPN's emitter current on and off. No tank loading at >>>>>> all. >>>>>> >>>>>>> >>>>>>> Here's an oscillator with diode+resistor clipping. The capacitor ratio >>>>>>> is extreme, 24:1, which in unconventional but makes the NPN run fairly >>>>>>> linear. >>>>>>> >>>>>>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/JL_LC_1.zip >>>>>>> >>>>>> >>>>>> You're pulling a big spike out of the top of the tank, though--put >>>>>> another of those 1m resistors between the tank and the collector, and >>>>>> you'll see. My PNP pulls almost all capacitive current out of the top >>>>>> of the tank, and there aren't any spikes there. >>>>>> >>>>>>> >>>>>>> I guess the ideal circuit would use hard clipping at first and >>>>>>> gracefully transition to a slow leveling loop. The PNP sort of does >>>>>>> that, but its current is still spikey. If you don't mind the amplitude >>>>>>> changing 10 or 20% before it stabilizes, just a slowish loop would be >>>>>>> OK, and Q would benefit. >>>>>>> >>>>>> >>>>>> On the other hand, just rebiasing it so that it current limits instead >>>>>> of voltage limiting will increase the loaded Q by a large factor. A >>>>>> resistor between the emitter and the tank helps too. (Small capacitors >>>>>> also work.) >>>>>> >>>>>> For instance, your circuit (280 uA quiescent bias) gets a peak inductor >>>>>> current of 8 mA, whereas the one below (72 uA quiescent bias) peaks at >>>>>> 60 mA. So that's a factor of 30 reduction in loading, with a >>>>>> corresponding increase in loaded Q. >>>>>> >>>>>>> My circuit has the charm of simplicity, and settles fast, and may be >>>>>>> good enough for what I want to do. The overall PLL takes over after a >>>>>>> while, so extreme Q isn't really needed. >>>>>> >>>>>> Well, the higher the Q, the less vulnerable the resonator is to external >>>>>> effects. That has a direct impact on the jitter. >>>>> >>>>> Belay that. It's much better, but it still voltage-limits. Revised >>>>> version coming soon to a simulator near you. >>>>> >>>>> Cheers >>>>> >>>>> Phil Hobbs >>>>> >>>>> >>>> Okay, it's fixed. This one works essentially the same over a 6:1 range >>>> of Q_L (100 to 600 milliohms out of 60-odd ohms). With < 50 uA >>>> quiescent bias, it has circulating currents of 8-10 mA in the tank, and >>>> amplitude limiting is controlled by the transconductance of the NPN. >>> >>> Thanks. >>> >>> The initial amplitude is dependent on the 220R. What else does it depend >>> on? May need to make that a trimpot. >> >> Whenever I mention "trimpot" the kids here start calling assisted-care >> retirement facilities to ship me off to. >> >> My only objection to a trimpot here is, how would you set it? You can >> hardly probe the tank without upsetting it. > >I don't think there's a need, if the comparator threshold is near >ground. Amplitude is a second-order effect then. > >Cheers > >Phil HobbsPretty much. The first couple edges wobble a bit, but that could be all sorts of things, including stuff inside the comparator. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●December 17, 20152015-12-17
On 17/12/15 11:42, John Larkin wrote:> On Thu, 17 Dec 2015 10:46:41 +1100, Clifford Heath > <no.spam@please.net> wrote: > >> On 17/12/15 09:22, Phil Hobbs wrote: >>> On 12/16/2015 01:16 PM, Phil Hobbs wrote: >>>> On 12/16/2015 01:08 PM, Phil Hobbs wrote: >>>>> On 12/16/2015 12:30 PM, John Larkin wrote: >>>>>> On Wed, 16 Dec 2015 10:19:08 -0500, Phil Hobbs >>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>> >>>>>>> On 12/16/2015 04:06 AM, piglet wrote: >>>>>>>> On 15/12/2015 16:30, Phil Hobbs wrote: >>>>>>>>>> Cute. I might be more inclined to turn the ALC transistor >>>>>>>>>> upside down >>>>>>>>>> and use a PNP. That would avoid loading the emitter of the >>>>>>>>>> oscillator >>>>>>>>>> transistor. >>>>>>>>> >>>>>>>>> Come to think about it, by omitting the diode and cap, connecting >>>>>>>>> the >>>>>>>>> PNP's base to the NPN's collector, and putting a bit of positive >>>>>>>>> bias >>>>>>>>> on the PNP's emitter, it could kill the NPN's collector current >>>>>>>>> before >>>>>>>>> saturation occurs. That wouldn't have any slow bias TCs. >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> >>>>>>>>> Phil Hobbs >>>>>>>>> >>>>>>>> >>>>>>>> That is a very neat idea, true cycle by cycle control, the tank Q >>>>>>>> will >>>>>>>> clean up the even harmonic distortion. >>>>>>>> >>>>>>>> piglet >>>>>>>> >>>>>>> >>>>>>> Seems to work all right, though there's some loading from the PNP's >>>>>>> base, which seems to be mostly capacitive. >>>>>> >>>>>> That seems to me to be about equivalent to diode clipping the tank to >>>>>> limit amplitude, or at least diode clipping with a bit of added series >>>>>> resistance to soften things up. >>>>> >>>>> I don't think so, on account of the beta of the PNP, which reduces the >>>>> tank loading (which is more or less the point of the exercise). At >>>>> those sorts of speeds, it's probably possible to use a PNP Darlington. >>>>> >>>>> The gain-limiting current is still >>>>>> mostly short, peak-of-sine spikes. They are applied to the capacitor >>>>>> tap, not to the top of the tank, but then are correspondingly bigger. >>>>>> >>>>>> A slow AGC would gradually reduce the loop gain, but that would be, >>>>>> well, slow. Any fast AGC must look ohmic to the tank and thus kill Q. >>>>> >>>>> If the PNP's beta and Early voltage were infinite, it would look exactly >>>>> like switching the NPN's emitter current on and off. No tank loading at >>>>> all. >>>>> >>>>>> >>>>>> Here's an oscillator with diode+resistor clipping. The capacitor ratio >>>>>> is extreme, 24:1, which in unconventional but makes the NPN run fairly >>>>>> linear. >>>>>> >>>>>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/JL_LC_1.zip >>>>>> >>>>> >>>>> You're pulling a big spike out of the top of the tank, though--put >>>>> another of those 1m resistors between the tank and the collector, and >>>>> you'll see. My PNP pulls almost all capacitive current out of the top >>>>> of the tank, and there aren't any spikes there. >>>>> >>>>>> >>>>>> I guess the ideal circuit would use hard clipping at first and >>>>>> gracefully transition to a slow leveling loop. The PNP sort of does >>>>>> that, but its current is still spikey. If you don't mind the amplitude >>>>>> changing 10 or 20% before it stabilizes, just a slowish loop would be >>>>>> OK, and Q would benefit. >>>>>> >>>>> >>>>> On the other hand, just rebiasing it so that it current limits instead >>>>> of voltage limiting will increase the loaded Q by a large factor. A >>>>> resistor between the emitter and the tank helps too. (Small capacitors >>>>> also work.) >>>>> >>>>> For instance, your circuit (280 uA quiescent bias) gets a peak inductor >>>>> current of 8 mA, whereas the one below (72 uA quiescent bias) peaks at >>>>> 60 mA. So that's a factor of 30 reduction in loading, with a >>>>> corresponding increase in loaded Q. >>>>> >>>>>> My circuit has the charm of simplicity, and settles fast, and may be >>>>>> good enough for what I want to do. The overall PLL takes over after a >>>>>> while, so extreme Q isn't really needed. >>>>> >>>>> Well, the higher the Q, the less vulnerable the resonator is to external >>>>> effects. That has a direct impact on the jitter. >>>> >>>> Belay that. It's much better, but it still voltage-limits. Revised >>>> version coming soon to a simulator near you. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>>> >>>> >>> Okay, it's fixed. This one works essentially the same over a 6:1 range >>> of Q_L (100 to 600 milliohms out of 60-odd ohms). With < 50 uA >>> quiescent bias, it has circulating currents of 8-10 mA in the tank, and >>> amplitude limiting is controlled by the transconductance of the NPN. >> >> Thanks. >> >> The initial amplitude is dependent on the 220R. What else does it depend >> on? May need to make that a trimpot. > > Whenever I mention "trimpot" the kids here start calling assisted-care > retirement facilities to ship me off to. > > My only objection to a trimpot here is, how would you set it? You can > hardly probe the tank without upsetting it.Your CRO can see it. Your comparator also has to see the crossings without moving them. You need a fairly high-impedance take-off in both cases, such as the RF probe amplifier I published here a few months back.> With 2% Ls and Cs and reasonable care as regards idle current, the > startup amplitude should be pretty close. We already expect the first > cycle or to to be some picoseconds off schedule, and we calibrate for > that.Yep, all good - but if you wanted a sudden-on sinewave generator as a test instrument, you need to get it right. I'm not sure what one would be indispensable for, but it seems like there must be some application. Clifford Heath.
Reply by ●December 17, 20152015-12-17
On Wednesday, December 16, 2015 at 8:06:51 PM UTC-8, Clifford Heath wrote:> > ... if you wanted a sudden-on sinewave generator as a > test instrument, you need to get it right. I'm not sure what one would > be indispensable for, but it seems like there must be some application.Yep; you trigger the oscillator on an event, then mix down the oscillator against a nearly-same-frequency time standard. Digitize and look at the phase of the beat signal, it tells you the event time offset from the time standard clock zero crossings. It's a way to add a vernier scale to a time measurement, picoseconds resolution from megahertz clocks.
Reply by ●December 17, 20152015-12-17
On Thu, 17 Dec 2015 00:38:46 -0800 (PST), whit3rd <whit3rd@gmail.com> wrote:>On Wednesday, December 16, 2015 at 8:06:51 PM UTC-8, Clifford Heath wrote: > >> >> ... if you wanted a sudden-on sinewave generator as a >> test instrument, you need to get it right. I'm not sure what one would >> be indispensable for, but it seems like there must be some application. > >Yep; you trigger the oscillator on an event, then mix down the oscillator against >a nearly-same-frequency time standard. Digitize and look at the phase >of the beat signal, it tells you the event time offset from the time standard >clock zero crossings. > >It's a way to add a vernier scale to a time measurement, picoseconds resolution >from megahertz clocks.That's the heterodyne triggered-oscillator PLL technique used by HP in their 5359A Time Synthesizer, copied by BNC and LeCroy and others. They all used varicap-tuned delay-line oscillators. The heterodyne thing is OK, but it has some nasty n-squared math tradeoffs that limit jitter performance. HP used two of them, and secondary heterodyning, in their excellent 5370 time-interval counter. The HP manuals are available, with full schematics and theory sections. Worth some study if you find that sort of electronics interesting. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●December 17, 20152015-12-17
