High Quality White Noise Gen
in [Design]
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From: Bill Sloman on 7 Jun 2010 05:16 On Jun 7, 4:39 am, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sun, 6 Jun 2010 19:19:03 -0700 (PDT),Bill Sloman > > > > <bill.slo...(a)ieee.org> wrote: > >On Jun 7, 3:41 am, John Larkin > ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Sun, 6 Jun 2010 15:37:19 -0700 (PDT),Bill Sloman > > >> <bill.slo...(a)ieee.org> wrote: > >> >On Jun 6, 10:36 pm, George Herold <gher...(a)teachspin.com> wrote: > >> >> On Jun 5, 6:52 pm, John Larkin > > >> >> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> > On Sat, 5 Jun 2010 15:00:09 -0700 (PDT),Bill Sloman > > >> >> > <bill.slo...(a)ieee.org> wrote: > >> >> > >On Jun 5, 8:18 pm, John Larkin > >> >> > ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> > >> On Sat, 5 Jun 2010 10:47:26 -0700 (PDT),Bill Sloman > > >> >> > >> <bill.slo...(a)ieee.org> wrote: > >> >> > >> >On Jun 5, 1:24 am, John Larkin > >> >> > >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> > >> >> On Fri, 4 Jun 2010 14:56:44 -0700 (PDT),Bill Sloman > > >> >> > >> >> <bill.slo...(a)ieee.org> wrote: > >> >> > >> >> >On Jun 4, 10:40 pm, Phil Hobbs > >> >> > >> >> ><pcdhSpamMeSensel...(a)electrooptical.net> wrote: > >> >> > >> >> >> On 6/4/2010 12:01 PM,Bill Slomanwrote: > > >> >> > >> >> >> > On Jun 4, 4:41 pm, George Herold<gher...(a)teachspin.com> wrote: > >> >> > >> >> >> >> On Jun 4, 10:07 am, Phil Hobbs > > >> >> > >> >> >> >> <pcdhSpamMeSensel...(a)electrooptical.net> wrote: > >> >> > >> >> >> >>> On 6/3/2010 11:12 PM, George Herold wrote: > > >> >> > >> >> >> >>>> langw...(a)fonz.dk wrote: > >> >> > >> >> >> >>>>> On 3 Jun., 23:11, Phil Hobbs<pcdhSpamMeSensel...(a)electrooptical.net> > >> >> > >> >> >> >>>>> wrote: > >> >> > >> >> >> >>>>>> On 6/3/2010 9:49 AM, George Herold wrote: > > >> >> > >> >> >> >>>>>>> On Jun 2, 4:36 pm, John Larkin > >> >> > >> >> >> >>>>>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> > >> >> >> >>>>>>>> On Wed, 2 Jun 2010 12:30:19 -0700 (PDT), George Herold > > >> >> > >> >> >> >>>>>>>> <gher...(a)teachspin.com> wrote: > >> >> > >> >> >> >>>>>>>>> On Jun 2, 1:59 pm, whit3rd<whit...(a)gmail.com> wrote: > >> >> > >> >> >> >>>>>>>>>> On Jun 2, 10:37 am, George Herold<gher...(a)teachspin.com> wrote: > > >> >> > ><snip> > > >> >> > >> >> >> > You might want to search on single photon avalanche photo-detection. > > >> >> > >> >> >> >http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-3-2232 > > >> >> > >> >> >> > I haven't looked at the full paper but the list of references includes > >> >> > >> >> >> > some useful stuff. > > >> >> > >> >> >> Geiger-mode APDs are mostly a crock unless you need timing accuracy > >> >> > >> >> >> better than, say, 10 ns. Their dark count rate is a good six orders of > >> >> > >> >> >> magnitude worse than a PMT of the same area, and their dead time is 10 > >> >> > >> >> >> times longer. > > >> >> > >> >> >> On the other hand, they don't die if you put them in a helium > >> >> > >> >> >> atmosphere, and they last longer than 5 years. > > >> >And they can offer single photon detection of longer wavelength > >> >photons than any photomultiplier tube can pick up. For some > >> >apllication this is vital. > > >> >> > >> >> >Horses for courses. They can be a lot more compact and robust than > >> >> > >> >> >PMTs - on which I'm rather more expert. > > >> >> > >> >> Vain fathead. > > >> >> > >> >I've worked with PMT's - which is more than I can claim about SPAD's - > >> >> > >> >and I've persuaded the IEEE that I do know a little about PMTs - see > >> >> > >> >the IEEE Transactions on Electronic Devices volume 38 pages 679-680, > >> >> > >> >published in March 1991. > > >> >> > >> >You do need to base your abuse on something more than your right-wing > >> >> > >> >intuition. Going off half-cocked like this does rather expose your > >> >> > >> >enthusiasm for believeing what you want to believe despite the absence > >> >> > >> >of any evidence to support your point of view. > > >> >> > >> All you do here is claim how "expert" you are, or maybe were, without > >> >> > >> ever making actual contributions. > > >> >> > >Nothing that you'd be willing to acknowledge, particularly since most > >> >> > >of my contributions are references to the publshed literature, a > >> >> > >source that you seem ill-equipped to exploit > > >> >> > >> You never *do* anything. > > >> >> > >Not at the moment, and I find it frustrating. > > >> >> > >> And when I don't have convincing evidence, I experiment and collect > >> >> > >> some. A mouse isn't a soldering iron. > > >> >> > >You burble about 140dB of ripple rejection > > >> >> > Burble? > > >> >> Maybe he say you coming through the turgey(sp) wood. > > >> Tulgey. > > >> >Charles Lutwidge Dodgson worked as an academic mathematician in the > >> >areas of geometry, matrix algebra and mathematical logic, none of > >> >which would appeal to John Larkin. > > >> I can recite "Jabberwocky" by heart, and do sometimes if the beer or > >> wine are of sufficient quality. > > >> This Bandit chardonnay here is actually pretty good. > > >My wife recently found an excuse to open some of our 2004 Gosset > >Polish Hill Riesling - last year she thought that the 2003 was better, > >but this year the 2004 does seem to come into its own. > > >http://www.grosset.com.au/wines_polishhillriesling.htm > > How can a wine critic know that the wine tastes of "glacial gravel, > slate and shale"? Does he munch on rocks for reference? > > I've seen a lot of "rock" references in wine criticism lately. "Hints > of cherry and apricot mold" are passe. Wine snobs are like > audiophools. Double-blind testing shows them as the delusional > fatheads that they are. Max Coltheart is a professor of cognitive psychology who has a long- running experiemnt in which he gives a talk about wines and wine tastng to academic audiences - including a variety of this kind of wine-tasting terminology - tests his audience's performance as wine tasters and records the results. He hasn't published it yet - and I took part in one such experiment nearly thirty years ago. Informally, I've heard from him that some phrases are more useful than others, but the communication is not all that analytical http://homepages.wmich.edu/~dilworth/Imaginative_versus_Analytical_Experiences_of_Wines.pdf Wine-tasters are anything but fat-headed, but their language is imprecise, if evocative. > There is a trend in California to buy tasty cheap wine. Makes sense to > me. It would. You aren't great of acquiring background knowledge. > http://www.enthusiasticspirits.com/r/products/three-thieves-bandit-pi... > > The other trend is bars and restaurants that serve "draft" wine, right > out of the barrel. Modern wines are often made to be instantly drinkable. This doesn't mean that they can't get better with age, but many don't. If the wine- maker has a gas-chromatograph - ideally with a tandem mass- spectrometer as a detector - they can have a very clear idea of what their wine tastes and smells like, and the good ones know how to create an attractive mixture of sensations, and have a pretty good idea of how that mixture will change and develop with time, It an art, and there are some great artist out there. Wolfgang Blass in Australia was an early pioneer of this approach, and while he isn't a great artist, I've drunk some very pleasant wines sold under his name. http://en.wikipedia.org/wiki/Wolf_Blass -- Bill Sloman, Nijmegen
From: George Herold on 7 Jun 2010 09:36 On Jun 7, 12:00 am, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sun, 6 Jun 2010 20:31:49 -0700 (PDT), George Herold > > > > > > <gher...(a)teachspin.com> wrote: > >On Jun 6, 9:35 pm, John Larkin > ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Sun, 6 Jun 2010 13:36:09 -0700 (PDT), George Herold > > >> <gher...(a)teachspin.com> wrote: > >> >On Jun 5, 6:52 pm, John Larkin > >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> On Sat, 5 Jun 2010 15:00:09 -0700 (PDT), Bill Sloman > > >> >> <bill.slo...(a)ieee.org> wrote: > >> >> >On Jun 5, 8:18 pm, John Larkin > >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> On Sat, 5 Jun 2010 10:47:26 -0700 (PDT),Bill Sloman > > >> >> >> <bill.slo...(a)ieee.org> wrote: > >> >> >> >On Jun 5, 1:24 am, John Larkin > >> >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> >> On Fri, 4 Jun 2010 14:56:44 -0700 (PDT),Bill Sloman > > >> >> >> >> <bill.slo...(a)ieee.org> wrote: > >> >> >> >> >On Jun 4, 10:40 pm, Phil Hobbs > >> >> >> >> ><pcdhSpamMeSensel...(a)electrooptical.net> wrote: > >> >> >> >> >> On 6/4/2010 12:01 PM,Bill Slomanwrote: > > >> >> >> >> >> > On Jun 4, 4:41 pm, George Herold<gher...(a)teachspin.com> wrote: > >> >> >> >> >> >> On Jun 4, 10:07 am, Phil Hobbs > > >> >> >> >> >> >> <pcdhSpamMeSensel...(a)electrooptical.net> wrote: > >> >> >> >> >> >>> On 6/3/2010 11:12 PM, George Herold wrote: > > >> >> >> >> >> >>>> langw...(a)fonz.dk wrote: > >> >> >> >> >> >>>>> On 3 Jun., 23:11, Phil Hobbs<pcdhSpamMeSensel...(a)electrooptical.net> > >> >> >> >> >> >>>>> wrote: > >> >> >> >> >> >>>>>> On 6/3/2010 9:49 AM, George Herold wrote: > > >> >> >> >> >> >>>>>>> On Jun 2, 4:36 pm, John Larkin > >> >> >> >> >> >>>>>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> >> >> >>>>>>>> On Wed, 2 Jun 2010 12:30:19 -0700 (PDT), George Herold > > >> >> >> >> >> >>>>>>>> <gher...(a)teachspin.com> wrote: > >> >> >> >> >> >>>>>>>>> On Jun 2, 1:59 pm, whit3rd<whit...(a)gmail.com> wrote: > >> >> >> >> >> >>>>>>>>>> On Jun 2, 10:37 am, George Herold<gher...(a)teachspin.com> wrote: > > >> >> ><snip> > > >> >> >> >> >> > You might want to search on single photon avalanche photo-detection. > > >> >> >> >> >> >http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-3-2232 > > >> >> >> >> >> > I haven't looked at the full paper but the list of references includes > >> >> >> >> >> > some useful stuff. > > >> >> >> >> >> Geiger-mode APDs are mostly a crock unless you need timing accuracy > >> >> >> >> >> better than, say, 10 ns. Their dark count rate is a good six orders of > >> >> >> >> >> magnitude worse than a PMT of the same area, and their dead time is 10 > >> >> >> >> >> times longer. > > >> >> >> >> >> On the other hand, they don't die if you put them in a helium > >> >> >> >> >> atmosphere, and they last longer than 5 years. > > >> >> >> >> >Horses for courses. They can be a lot more compact and robust than > >> >> >> >> >PMTs - on which I'm rather more expert. > > >> >> >> >> Vain fathead. > > >> >> >> >I've worked with PMT's - which is more than I can claim about SPAD's - > >> >> >> >and I've persuaded the IEEE that I do know a little about PMTs - see > >> >> >> >the IEEE Transactions on Electronic Devices volume 38 pages 679-680, > >> >> >> >published in March 1991. > > >> >> >> >You do need to base your abuse on something more than your right-wing > >> >> >> >intuition. Going off half-cocked like this does rather expose your > >> >> >> >enthusiasm for believeing what you want to believe despite the absence > >> >> >> >of any evidence to support your point of view. > > >> >> >> All you do here is claim how "expert" you are, or maybe were, without > >> >> >> ever making actual contributions. > > >> >> >Nothing that you'd be willing to acknowledge, particularly since most > >> >> >of my contributions are references to the publshed literature, a > >> >> >source that you seem ill-equipped to exploit > > >> >> >> You never *do* anything. > > >> >> >Not at the moment, and I find it frustrating. > > >> >> >> And when I don't have convincing evidence, I experiment and collect > >> >> >> some. A mouse isn't a soldering iron. > > >> >> >You burble about 140dB of ripple rejection > > >> >> Burble? > >> >Maybe he say you coming through the turgey(sp) wood. > > >> >> I questioned whether the Spice models of the c-multiplier were > >> >> accurate at mid-frequencies. None came close to 140, or even 80, dB at > >> >> frequencies where Early slope matters. So I tried some experiments. > > >> >The Early effect goes away at at high frequencies? > > >> No, but the optput capacitor impedance continues to decline. > > >> There are a few frequency zones: > > >> Dc to where the base lowpass filter kicks in: 0 dB ripple attenuation. > > >> A region where the Early thing works, roughly -50 dB. > > >> A slope downward, beginning at the corner frequency set by Re and the > >> output filter capacitance Cf. > > >Ahh excellent. It's this one that makes it not work so well when I > >load the output too much. (Or do I just need a bigger cap?) > > At modest currents, emitter dynamic resistance Re is inverse on > current, actually about 25 ohms divided by emitter current in mA. So > the corner frequency of Re * Cl changes with load. I don't know how > the Early feedthrough changes with load current. > > Capacitor ESR also forms a voltage divider with Re, so yet more ripple > blasts through as Re goes down at higher currents. Yup, It's all making sense. A few years ago a made a bunch of RC lowpasses and measured ESR's. I came to the conclusion that you couldn't expect anything much lower than 0.1 ohms. But I didn't try any really big Al electro's (>100's uF) George H. > > Not a simple circuit! > > John- Hide quoted text - > > - Show quoted text -
From: George Herold on 7 Jun 2010 09:48 On Jun 7, 12:10 am, Phil Hobbs <pcdhSpamMeSensel...(a)electrooptical.net> wrote: > George Herold wrote: > > On Jun 4, 4:40 pm, Phil Hobbs <pcdhSpamMeSensel...(a)electrooptical.net> > > wrote: > >> On 6/4/2010 12:01 PM, Bill Sloman wrote: > > >>> On Jun 4, 4:41 pm, George Herold<gher...(a)teachspin.com> wrote: > >>>> On Jun 4, 10:07 am, Phil Hobbs > >>>> <pcdhSpamMeSensel...(a)electrooptical.net> wrote: > >>>>> On 6/3/2010 11:12 PM, George Herold wrote: > >>>>>> langw...(a)fonz.dk wrote: > >>>>>>> On 3 Jun., 23:11, Phil Hobbs<pcdhSpamMeSensel...(a)electrooptical.net> > >>>>>>> wrote: > >>>>>>>> On 6/3/2010 9:49 AM, George Herold wrote: > >>>>>>>>> On Jun 2, 4:36 pm, John Larkin > >>>>>>>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >>>>>>>>>> On Wed, 2 Jun 2010 12:30:19 -0700 (PDT), George Herold > >>>>>>>>>> <gher...(a)teachspin.com> wrote: > >>>>>>>>>>> On Jun 2, 1:59 pm, whit3rd<whit...(a)gmail.com> wrote: > >>>>>>>>>>>> On Jun 2, 10:37 am, George Herold<gher...(a)teachspin.com> wrote: > >>>>>>>>>>>>>>>>> Yup, and if the voltage asymmetry is a problem you can add the signal > >>>>>>>>>>>>>>>> >from two diodes, one biased from the positve supply and the other from > >>>>>>>>>>>>>>>>> the negative. > >>>>>>>>>>>>> Hmmm, you are right.... I still don't think that summing the voltage > >>>>>>>>>>>>> noise from a bunch of unipolarized zeners is going to get rid of the > >>>>>>>>>>>>> voltage asymmetry. > >>>>>>>>>>>> You can use two zeners on a single power supply, in bridge > >>>>>>>>>>>> configuration; couple the output through a transformer to get > >>>>>>>>>>>> the difference. Symmetry is guaranteed if you balance the bridge > >>>>>>>>>>>> correctly. > >>>>>>>>>>> Ahh, more than one way to skin that cat. > >>>>>>>>>>> Say speaking of noise sources, a colleague put together a digital > >>>>>>>>>>> noise source. A counter steps through a look up table that feeds a > >>>>>>>>>>> DAC. The lookup table holds a whole comb of sine waves equally spaced > >>>>>>>>>>> in frequency space up to 32kHz. (I don t recall the frequency spacing > >>>>>>>>>>> but I could find out.. a few Hz or so.) The phases of all the sine > >>>>>>>>>>> waves were chosen randomly. The DAC was 12 bit (an AD7541 I > >>>>>>>>>>> think). The whole thing was clocked several times lower than Nyquist > >>>>>>>>>>> limit (~128 kHz). Now the problem we observed, (and could never > >>>>>>>>>>> cure), was intermodulation distortion above the 32 kHz cutoff.. The > >>>>>>>>>>> signals above the cutoff frequency were down by only 50 dB, and my > >>>>>>>>>>> colleague was expecting something closer to 70 dB down. (Is that > >>>>>>>>>>> right for 12 bit resolution on the DAC? ) I worked on all the layout > >>>>>>>>>>> and analog portions of the circuit but could never make it any > >>>>>>>>>>> better. There was talk about clock jitter on SED recently and I > >>>>>>>>>>> wondered if this could be the source of the problem? Or maybe you > >>>>>>>>>>> have some other idea. > >>>>>>>>>> The DAC quantization, and any nonlinearity, will add harmonic > >>>>>>>>>> distortion. Plus the sines may occasionally peak together and clip the > >>>>>>>>>> dac. Plus it's not trivial to get -70 dB distortion at these > >>>>>>>>>> frequencies. > >>>>>>>>>> We use random number generators and boxcar filters to generate > >>>>>>>>>> Gaussian noise to feed into dacs. This little box does this, all in a > >>>>>>>>>> Spartan3 FPGA... > >>>>>>>>>>http://www.highlandtechnology.com/DSS/T346DS.html > >>>>>>>>>> Rob cleverly, somehow, allowed the user to program the noise bandwidth > >>>>>>>>>> from mHz to 2 MHz without affecting the RMS amplitude. > >>>>>>>>> Very nice, (Are prices listed on your website?) Y'all make stuff > >>>>>>>>> that's several orders of magnitude above what we're doing. > >>>>>>>>> You know what I'd really like to make (and could probabbly sell too.) > >>>>>>>>> is a random pulse generator. Short little pulses maybe 10nS or less > >>>>>>>>> coming at an average rate of 1us or so. This would be a psuedo shot > >>>>>>>>> noise generator. With a pot on the output one could change the > >>>>>>>>> amplitude of the pulses and see how the noise scaled. ... Hmm it > >>>>>>>>> would be nicer if the average pulse rate could be changed too. So > >>>>>>>>> that one could keep the average 'current' the same, but made with > >>>>>>>>> bigger 'electrons'. Sounds like a digital circuit. (Which I find a > >>>>>>>>> bit boring) an analog 'something' would be more fun. > >>>>>>>>> George H. > >>>>>>>>>> John- Hide quoted text - > >>>>>>>>>> - Show quoted text - > >>>>>>>> How about avalanching a phototransistor? ;) > >>>>>>> point it at an Americium source from a smokedetector :) > >>>>>>> real random noise > >>>>>> Something optical is nice because you can change light intensity with > >>>>>> a knob. > >>>>>> George H. > >>>>>>> -Lasse > >>>>> I was just janking your chain--I had no idea that anybody had actually > >>>>> tried that. Phototransistors are so horrible on so many levels that > >>>>> it's pretty amusing to see someone trying to make fast pulses out of them. > >>>>> Cheers > >>>>> Phil Hobbs > >>>>> - Show quoted text - > >>>> Oh...(Silly me) Well so how 'bout a photo-transistor with three > >>>> terminals (one where the base has a lead connected to it.) I'll short > >>>> the base and collector together and then reverse bias the EB > >>>> junction. With the bias voltage set just below where the thing wants > >>>> to zener. Then a photon could set the whole thing off? > >>>> I thought I had a photo transistor around here someplace, but I > >>>> couldn't find it. (The original prototype of optical puming used a > >>>> phototransistor, until I convinced every one that a photodiode was, > >>>> more sensitive (larger area), less noisy and faster.) > >>>> Ahh the other silly thought that this generated was using an avalanche > >>>> zener diode as a photo detector. I know the Zener's I use are > >>>> sensitive to light, so again if I was to park them just below the knee > >>>> voltage and then hit them with light could I get some gain out of > >>>> them? Kinda a poor man's APD. > >>> You might want to search on single photon avalanche photo-detection. > >>>http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-3-2232 > >>> I haven't looked at the full paper but the list of references includes > >>> some useful stuff. > >>> -- > >>> Bill Sloman, Nijmegen > >> Geiger-mode APDs are mostly a crock unless you need timing accuracy > >> better than, say, 10 ns. Their dark count rate is a good six orders of > >> magnitude worse than a PMT of the same area, and their dead time is 10 > >> times longer. > > >> On the other hand, they don't die if you put them in a helium > >> atmosphere, and they last longer than 5 years. > > >> Cheers > > >> Phil Hobbs > > >> - Show quoted text - > > > PMT's and APD's are too expensive, for a simulation, PD shot noise > > should be easy, or a zener. (how much does an APD cost, in hundreds?) > > > George H. > > The nice thing about PIN photodiodes is that there's a first-principles > relationship between the DC and noise currents. That's a great > calibration principle for instruments. Yeah, Lafe Spietz does shot noise thermometry with tunnel junction diodes. I've got an idea for a similar circuit trick that will, balance shot noise and johnson noise to measure temperature... The shot noise gives you the circuit gain and bandwidth, which then drop out in a ratio.... looks good on paper but I still have to try it. (You run the same DC current from the shot noise through the resistor that gives you the johnson noise and it's DC voltage is then the thermal voltage. (or maybe two times it.) George H. > I have about 100 InGaAs APD/preamp modules that I got for about 75 cents > each--probably 0.5 cents on the dollar. > > Cheers > > Phil Hobbs > > -- > Dr Philip C D Hobbs > Principal > ElectroOptical Innovations > 55 Orchard Rd > Briarcliff Manor NY 10510 > 845-480-2058 > hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text - > > - Show quoted text -
From: John Larkin on 7 Jun 2010 09:55 On Mon, 7 Jun 2010 02:16:57 -0700 (PDT), Bill Sloman <bill.sloman(a)ieee.org> wrote: >Modern wines are often made to be instantly drinkable. This doesn't >mean that they can't get better with age, but many don't. If the wine- >maker has a gas-chromatograph - ideally with a tandem mass- >spectrometer as a detector - they can have a very clear idea of what >their wine tastes and smells like, and the good ones know how to >create an attractive mixture of sensations, and have a pretty good >idea of how that mixture will change and develop with time, Can a GC tell that the vines grew in water that had been filtered through glacial gravel, slate and shale? John
From: John Larkin on 7 Jun 2010 09:58
On Mon, 7 Jun 2010 06:36:02 -0700 (PDT), George Herold <gherold(a)teachspin.com> wrote: >On Jun 7, 12:00�am, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Sun, 6 Jun 2010 20:31:49 -0700 (PDT), George Herold >> >> >> >> >> >> <gher...(a)teachspin.com> wrote: >> >On Jun 6, 9:35 pm, John Larkin >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> On Sun, 6 Jun 2010 13:36:09 -0700 (PDT), George Herold >> >> >> <gher...(a)teachspin.com> wrote: >> >> >On Jun 5, 6:52 pm, John Larkin >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> On Sat, 5 Jun 2010 15:00:09 -0700 (PDT), Bill Sloman >> >> >> >> <bill.slo...(a)ieee.org> wrote: >> >> >> >On Jun 5, 8:18 pm, John Larkin >> >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> >> On Sat, 5 Jun 2010 10:47:26 -0700 (PDT),Bill Sloman >> >> >> >> >> <bill.slo...(a)ieee.org> wrote: >> >> >> >> >On Jun 5, 1:24 am, John Larkin >> >> >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> >> >> On Fri, 4 Jun 2010 14:56:44 -0700 (PDT),Bill Sloman >> >> >> >> >> >> <bill.slo...(a)ieee.org> wrote: >> >> >> >> >> >On Jun 4, 10:40 pm, Phil Hobbs >> >> >> >> >> ><pcdhSpamMeSensel...(a)electrooptical.net> wrote: >> >> >> >> >> >> On 6/4/2010 12:01 PM,Bill Slomanwrote: >> >> >> >> >> >> >> > On Jun 4, 4:41 pm, George Herold<gher...(a)teachspin.com> wrote: >> >> >> >> >> >> >> On Jun 4, 10:07 am, Phil Hobbs >> >> >> >> >> >> >> >> <pcdhSpamMeSensel...(a)electrooptical.net> wrote: >> >> >> >> >> >> >>> On 6/3/2010 11:12 PM, George Herold wrote: >> >> >> >> >> >> >> >>>> langw...(a)fonz.dk wrote: >> >> >> >> >> >> >>>>> On 3 Jun., 23:11, Phil Hobbs<pcdhSpamMeSensel...(a)electrooptical.net> >> >> >> >> >> >> >>>>> wrote: >> >> >> >> >> >> >>>>>> On 6/3/2010 9:49 AM, George Herold wrote: >> >> >> >> >> >> >> >>>>>>> On Jun 2, 4:36 pm, John Larkin >> >> >> >> >> >> >>>>>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> >> >> >> >>>>>>>> On Wed, 2 Jun 2010 12:30:19 -0700 (PDT), George Herold >> >> >> >> >> >> >> >>>>>>>> <gher...(a)teachspin.com> wrote: >> >> >> >> >> >> >>>>>>>>> On Jun 2, 1:59 pm, whit3rd<whit...(a)gmail.com> wrote: >> >> >> >> >> >> >>>>>>>>>> On Jun 2, 10:37 am, George Herold<gher...(a)teachspin.com> wrote: >> >> >> >> ><snip> >> >> >> >> >> >> >> > You might want to search on single photon avalanche photo-detection. >> >> >> >> >> >> >> >http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-3-2232 >> >> >> >> >> >> >> > I haven't looked at the full paper but the list of references includes >> >> >> >> >> >> > some useful stuff. >> >> >> >> >> >> >> Geiger-mode APDs are mostly a crock unless you need timing accuracy >> >> >> >> >> >> better than, say, 10 ns. Their dark count rate is a good six orders of >> >> >> >> >> >> magnitude worse than a PMT of the same area, and their dead time is 10 >> >> >> >> >> >> times longer. >> >> >> >> >> >> >> On the other hand, they don't die if you put them in a helium >> >> >> >> >> >> atmosphere, and they last longer than 5 years. >> >> >> >> >> >> >Horses for courses. They can be a lot more compact and robust than >> >> >> >> >> >PMTs - on which I'm rather more expert. >> >> >> >> >> >> Vain fathead. >> >> >> >> >> >I've worked with PMT's - which is more than I can claim about SPAD's - >> >> >> >> >and I've persuaded the IEEE that I do know a little about PMTs - see >> >> >> >> >the IEEE Transactions on Electronic Devices volume 38 pages 679-680, >> >> >> >> >published in March 1991. >> >> >> >> >> >You do need to base your abuse on something more than your right-wing >> >> >> >> >intuition. Going off half-cocked like this does rather expose your >> >> >> >> >enthusiasm for believeing what you want to believe despite the absence >> >> >> >> >of any evidence to support your point of view. >> >> >> >> >> All you do here is claim how "expert" you are, or maybe were, without >> >> >> >> ever making actual contributions. >> >> >> >> >Nothing that you'd be willing to acknowledge, particularly since most >> >> >> >of my contributions are references to the publshed literature, a >> >> >> >source that you seem ill-equipped to exploit >> >> >> >> >> You never *do* anything. >> >> >> >> >Not at the moment, and I find it frustrating. >> >> >> >> >> And when I don't have convincing evidence, I experiment and collect >> >> >> >> some. A mouse isn't a soldering iron. >> >> >> >> >You burble about 140dB of ripple rejection >> >> >> >> Burble? >> >> >Maybe he say you coming through the turgey(sp) wood. >> >> >> >> I questioned whether the Spice models of the c-multiplier were >> >> >> accurate at mid-frequencies. None came close to 140, or even 80, dB at >> >> >> frequencies where Early slope matters. So I tried some experiments. >> >> >> >The Early effect goes away at at high frequencies? >> >> >> No, but the optput capacitor impedance continues to decline. >> >> >> There are a few frequency zones: >> >> >> Dc to where the base lowpass filter kicks in: 0 dB ripple attenuation. >> >> >> A region where the Early thing works, roughly -50 dB. >> >> >> A slope downward, beginning at the corner frequency set by Re and the >> >> output filter capacitance Cf. >> >> >Ahh excellent. �It's this one that makes it not work so well when I >> >load the output too much. �(Or do I just need a bigger cap?) >> >> At modest currents, emitter dynamic resistance Re is inverse on >> current, actually about 25 ohms divided by emitter current in mA. So >> the corner frequency of Re * Cl changes with load. I don't know how >> the Early feedthrough changes with load current. >> >> Capacitor ESR also forms a voltage divider with Re, so yet more ripple >> blasts through as Re goes down at higher currents. > >Yup, It's all making sense. A few years ago a made a bunch of RC >lowpasses and measured ESR's. I came to the conclusion that you >couldn't expect anything much lower than 0.1 ohms. But I didn't try >any really big Al electro's (>100's uF) The 120 uF polymer aluminums I'm using are 25 milliohms typ. I use one to LC filter the +15 from the wart, another at the c-mult output. Each takes about a quarter of a square inch of PCB surface, not too bad. John |