> tank Qyour velcome Mark
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
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.
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.
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
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
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. 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. Here's an older design, one I hope to both simplify and improve. https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/Burst_Sine.JPG https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/Burst_Osc_2.JPG It's untweaked, a production unit. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On 12/16/2015 06:46 PM, Clifford Heath 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. >>> >>> >> 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.Right. The equilibrium amplitude depends on the tank Q, and matching that with the kickstart amplitude is required if one wants to avoid the envelope transient. OTOH if you're just using a comparator to look for zero crossings, the amplitude is a second-order effect anyway. 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
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.
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. Cheers Phil Hobbs ============== Version 4 SHEET 1 1968 680 WIRE 576 -64 512 -64 WIRE 512 -48 512 -64 WIRE 16 -32 -32 -32 WIRE -32 0 -32 -32 WIRE 16 0 16 -32 WIRE 224 16 160 16 WIRE 240 16 224 16 WIRE 320 16 240 16 WIRE 464 16 320 16 WIRE 576 16 576 -64 WIRE 576 16 560 16 WIRE 592 16 576 16 WIRE 752 16 672 16 WIRE 752 48 752 16 WIRE 160 64 160 16 WIRE 320 64 320 16 WIRE 16 112 16 80 WIRE 96 112 16 112 WIRE 240 112 240 16 WIRE 16 128 16 112 WIRE 752 144 752 128 WIRE 160 192 160 160 WIRE 240 192 240 176 WIRE 240 192 224 192 WIRE 320 192 320 144 WIRE 16 208 16 192 WIRE 160 208 160 192 WIRE 240 208 240 192 WIRE 240 288 240 272 WIRE 320 288 320 272 WIRE 320 288 240 288 WIRE -96 304 -112 304 WIRE 16 304 16 272 WIRE 16 304 -16 304 WIRE 160 304 160 288 WIRE 160 304 16 304 WIRE 320 320 320 288 WIRE -112 336 -112 304 FLAG -112 336 0 FLAG 320 320 0 FLAG 752 144 0 FLAG 224 16 TANK FLAG 16 112 BASE FLAG -32 0 0 SYMBOL npn 96 64 R0 WINDOW 3 11 -18 Left 2 SYMATTR Value BFT25A SYMATTR InstName Q1 SYMBOL ind 304 48 R0 WINDOW 3 30 120 Left 2 SYMATTR Value 220n SYMATTR InstName L1 SYMATTR SpiceLine Rser=0 Rpar=1T SYMBOL res 176 192 M0 SYMATTR InstName R1 SYMATTR Value 10k SYMBOL voltage -112 304 R270 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL cap 224 112 R0 SYMATTR InstName C1 SYMATTR Value 56p SYMBOL cap 224 208 R0 SYMATTR InstName C2 SYMATTR Value 120p SYMBOL cap 160 208 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName C3 SYMATTR Value 22p SYMBOL res 304 176 R0 SYMATTR InstName R2 SYMATTR Value {Rser} SYMBOL res 576 32 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R3 SYMATTR Value 220 SYMBOL voltage 752 32 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName !GO SYMATTR Value PULSE(3.3 0 50n 500p 500p) SYMBOL npn 560 -48 R90 SYMATTR InstName Q2 SYMATTR Value BFT25A SYMBOL diode 0 128 R0 WINDOW 3 -85 31 Left 2 SYMATTR InstName D1 SYMATTR Value 1N914 SYMBOL res 0 -16 R0 SYMATTR InstName R4 SYMATTR Value 2k SYMBOL diode 0 208 R0 WINDOW 0 36 30 Left 2 WINDOW 3 -80 8 Left 2 SYMATTR InstName D2 SYMATTR Value 1N914 TEXT 488 344 Left 2 !.tran 100u TEXT 936 -136 Invisible 2 !.MODEL BFT25A NPN( IS = 1.3775E-017 BF = 85.654 NF = .9799 VAF = 50.805\n+ IKF = 10 ISE = 2.1998E-015 NE = 1.85715 BR = 16.975 NR = .98551\n+ VAR = 2.49144 IKR = .188014 ISC = 2.0516E-016 NC = 1.1073 RB = 80\n+ IRB = 1E-006 RBM = 80 RE = 7.911 RC = 5.3 EG = 1.11 XTI = 3\n+ CJE = 2.2303E-013 VJE = .6697 MJE = 5.9664E-002 TF = 5.1121E-012\n+ XTF = 7.9092 VTF = 1.3388 ITF = 5.6626E-003 PTF = 15.3714\n+ CJC = 2.2902E-013 VJC = .394786 MJC = 4.3323E-002 XCJC = .05\n+ TR = 1.3269E-008 VJS = .75 FC = .987824) TEXT 928 128 Invisible 2 !.MODEL BFT92 PNP( IS = 4.3756E-016 BF = 33.5815 NF = 1.0097 VAF = 23.3946\n+ IKF = 9.9538E-002 ISE = 8.7054E-014 NE = 1.94395 BR = 4.9472\n+ NR = 1.00254 VAR = 3.90385 IKR = 5.2816E-003 ISC = 3.5886E-014\n+ NC = 1.3933 RB = 5 IRB = 1E-006 RBM = 5 RE = 1 RC = 10 EG = 1.11\n+ XTI = 3 CJE = 7.4666E-013 VJE = .6 MJE = .35683 TF = 1.7492E-011\n+ XTF = 1.3546 VTF = .155654 ITF = 1E-003 PTF = 45 CJC = 9.371E-013\n+ VJC = .396455 MJC = .19995 XCJC = .106 TR = 8.422E-009\n+ VJS = .75 FC = .767856) TEXT 424 304 Left 2 !.step param Rser 100m 600m 100m -- 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