High Quality White Noise Gen
in [Design]
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From: Bill Sloman on 5 Jun 2010 13:50 On Jun 2, 10:25 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Wed, 2 Jun 2010 11:57:56 -0700 (PDT), George Herold > > > > <gher...(a)teachspin.com> wrote: > >On Jun 2, 1:46 pm, John Larkin > ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Wed, 2 Jun 2010 10:37:12 -0700 (PDT), George Herold > > >> <gher...(a)teachspin.com> wrote: > >> >On Jun 2, 10:55 am, John Larkin > >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> On Wed, 2 Jun 2010 07:32:55 -0700 (PDT), George Herold > > >> >> <gher...(a)teachspin.com> wrote: > >> >> >On Jun 1, 5:51 pm, John Larkin > >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> On Tue, 1 Jun 2010 11:35:59 -0700 (PDT), George Herold > > >> >> >> <gher...(a)teachspin.com> wrote: > >> >> >> >On May 31, 12:56 pm, John Larkin > >> >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> >> >> On Mon, 31 May 2010 12:23:10 GMT, jimsl...(a)esterlux.com (Jim Slone) > >> >> >> >> wrote: > > >> >> >> >> >What are the best options for high quality audio white noise > >> >> >> >> >generation? > > >> >> >> >> >I have been using generic diodes and reversed biased transistors. Then > >> >> >> >> >someone mentioned there are special parts available with better > >> >> >> >> >characteristics. > > >> >> >> >> >Can anyone please give me a pointer? > > >> >> >> >> >Jim Slone > > >> >> >> >> You can buy noise diodes from lots of people... just google <noise > >> >> >> >> diode> > > >> >> >> >Does anyone know what makes a high price "noise diode" any better than > >> >> >> >your garden variety Zener? > > >> >> >> Probably a very small junction area (for low capacitance, high current > >> >> >> density) and maybe some doping profile. Not a power device! > > >> >> >> Regular zeners get spikey and asymmetric and sort of oscillate at low > >> >> >> current. You can get noise diodes that behave at low currents. > > >> >> >> >> If you want really flat, really gaussian noise, a mathematical random > >> >> >> >> stream (single-bit) or random word (dac) generator is probably best. > >> >> >> >> See AoE for details. > > >> >> >> >> For audio, it doesn't matter much. A 10-volt zener biased at a few mA > >> >> >> >> is fine. > > >> >> >> >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. (Though I've never tried this trick.) > > >> >> >> Or sum the signals from a bunch of them. Central limit theorem. > > >> >> >Well that is not going to get rid of the voltage asymmetery. > > >> >> >If you need real Gaussian noise you can look at the shot noise from a > >> >> >photodiode illuminated by an LED. Gives you noise ~100 times bigger > >> >> >than the johnson noise of the sense resistor. (Assuming a 5 Volt DC > >> >> >drop across R). But this has one big drawback. It's very sensitve to > >> >> >vibrations. > > >> >> Shot noise is the ultimate asymmetric waveform. It's made of > >> >> single-photon unidirectional spikes. If it manages to be Gaussian, > >> >> it's because a lot of asymmetric signals are being summed. Central > >> >> limit theorem. > > >> >>http://en.wikipedia.org/wiki/Illustration_of_the_central_limit_theorem > > >> >> John- Hide quoted text - > > >> >> - Show quoted text - > > >> >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 assymetry. But I'd be happy to be wrong too. Have you ever > >> >tried this? It would be simple enough to put 5 or 6 together and see > >> >what the output looks like. (As long as you don't mind my summing > >> >with an opamp)... Maybe I can find some 'fun' time on Friday. > > >> >George H. > > >> The math says it must be so. Still, the sum would converge to Gaussian > >> faster if half of the lopsided signals were inverted. > > >OK I'll just have to try it. I find the math more convincing if I can > >see it in some experimental result. (Shot noise is a good example, > >but it s hard to get the current low enough so that you could see a > >non-Gaussian distribution.) > > >> Zener noise gets more symmetric at higher currents. 10 mA is usually > >> OK for a small 10-volt zener. > > >Yeah I think that is just the result of the I-V curvature. I'll try > >running them down at low currents where the asymmetry is larger. This > >is an experiment to show the central limit theorem and not make a good > >Gaussian noise source. > > >George H. > > >> I sometimes generate Gaussian-distributed numbers by summing a bunch > >> of RAN() calls, which are uniform on [0,1]. Six to ten works well, and > >> the crest factor is finite and known. > > >> John- Hide quoted text - > > >> - Show quoted text - > > Here is my elegant, peer-reviewed research paper on the subject: > > ftp://jjlarkin.lmi.net/Zener_Noise.pdf And the peer was peer of you brain-damaged right-wing friends? Such as James Arthur? -- Bill Sloman, Nijmegen
From: John Larkin on 5 Jun 2010 14:13 On Sat, 5 Jun 2010 10:50:25 -0700 (PDT), Bill Sloman <bill.sloman(a)ieee.org> wrote: >On Jun 2, 10:25�pm, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Wed, 2 Jun 2010 11:57:56 -0700 (PDT), George Herold >> >> >> >> <gher...(a)teachspin.com> wrote: >> >On Jun 2, 1:46 pm, John Larkin >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> On Wed, 2 Jun 2010 10:37:12 -0700 (PDT), George Herold >> >> >> <gher...(a)teachspin.com> wrote: >> >> >On Jun 2, 10:55 am, John Larkin >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> On Wed, 2 Jun 2010 07:32:55 -0700 (PDT), George Herold >> >> >> >> <gher...(a)teachspin.com> wrote: >> >> >> >On Jun 1, 5:51 pm, John Larkin >> >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> >> On Tue, 1 Jun 2010 11:35:59 -0700 (PDT), George Herold >> >> >> >> >> <gher...(a)teachspin.com> wrote: >> >> >> >> >On May 31, 12:56 pm, John Larkin >> >> >> >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> >> >> >> On Mon, 31 May 2010 12:23:10 GMT, jimsl...(a)esterlux.com (Jim Slone) >> >> >> >> >> wrote: >> >> >> >> >> >> >What are the best options for high quality audio white noise >> >> >> >> >> >generation? >> >> >> >> >> >> >I have been using generic diodes and reversed biased transistors. Then >> >> >> >> >> >someone mentioned there are special parts available with better >> >> >> >> >> >characteristics. >> >> >> >> >> >> >Can anyone please give me a pointer? >> >> >> >> >> >> >Jim Slone >> >> >> >> >> >> You can buy noise diodes from lots of people... just google <noise >> >> >> >> >> diode> >> >> >> >> >> >Does anyone know what makes a high price "noise diode" any better than >> >> >> >> >your garden variety Zener? >> >> >> >> >> Probably a very small junction area (for low capacitance, high current >> >> >> >> density) and maybe some doping profile. Not a power device! >> >> >> >> >> Regular zeners get spikey and asymmetric and sort of oscillate at low >> >> >> >> current. You can get noise diodes that behave at low currents. >> >> >> >> >> >> If you want really flat, really gaussian noise, a mathematical random >> >> >> >> >> stream (single-bit) or random word (dac) generator is probably best. >> >> >> >> >> See AoE for details. >> >> >> >> >> >> For audio, it doesn't matter much. A 10-volt zener biased at a few mA >> >> >> >> >> is fine. >> >> >> >> >> >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. (Though I've never tried this trick.) >> >> >> >> >> Or sum the signals from a bunch of them. Central limit theorem. >> >> >> >> >Well that is not going to get rid of the voltage asymmetery. >> >> >> >> >If you need real Gaussian noise you can look at the shot noise from a >> >> >> >photodiode illuminated by an LED. Gives you noise ~100 times bigger >> >> >> >than the johnson noise of the sense resistor. (Assuming a 5 Volt DC >> >> >> >drop across R). But this has one big drawback. It's very sensitve to >> >> >> >vibrations. >> >> >> >> Shot noise is the ultimate asymmetric waveform. It's made of >> >> >> single-photon unidirectional spikes. If it manages to be Gaussian, >> >> >> it's because a lot of asymmetric signals are being summed. Central >> >> >> limit theorem. >> >> >> >>http://en.wikipedia.org/wiki/Illustration_of_the_central_limit_theorem >> >> >> >> John- Hide quoted text - >> >> >> >> - Show quoted text - >> >> >> >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 assymetry. But I'd be happy to be wrong too. Have you ever >> >> >tried this? It would be simple enough to put 5 or 6 together and see >> >> >what the output looks like. (As long as you don't mind my summing >> >> >with an opamp)... Maybe I can find some 'fun' time on Friday. >> >> >> >George H. >> >> >> The math says it must be so. Still, the sum would converge to Gaussian >> >> faster if half of the lopsided signals were inverted. >> >> >OK I'll just have to try it. �I find the math more convincing if I can >> >see it in some experimental result. �(Shot noise is a good example, >> >but it s hard to get the current low enough so that you could see a >> >non-Gaussian distribution.) >> >> >> Zener noise gets more symmetric at higher currents. 10 mA is usually >> >> OK for a small 10-volt zener. >> >> >Yeah I think that is just the result of the I-V curvature. �I'll try >> >running them down at low currents where the asymmetry is larger. �This >> >is an experiment to show the central limit theorem and not make a good >> >Gaussian noise source. >> >> >George H. >> >> >> I sometimes generate Gaussian-distributed numbers by summing a bunch >> >> of RAN() calls, which are uniform on [0,1]. Six to ten works well, and >> >> the crest factor is finite and known. >> >> >> John- Hide quoted text - >> >> >> - Show quoted text - >> >> Here is my elegant, peer-reviewed research paper on the subject: >> >> ftp://jjlarkin.lmi.net/Zener_Noise.pdf > >And the peer was peer of you brain-damaged right-wing friends? Such as >James Arthur? When's the last time you did any real electronics? Or any real work? You resent me having James as a friend? I sure don't. He can cook, sing, and think. And ski, albeit sort of slowly. I mean, there's G, the slope, and the coefficient of friction of p-tex on ice. Why mess with that? John
From: John Larkin on 5 Jun 2010 14:18 On Sat, 5 Jun 2010 10:47:26 -0700 (PDT), Bill Sloman <bill.sloman(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: >> >> >> >>>>>>>>>>>>>>> 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 >> >> >> >>> -- >> >> >>> 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-Hidequotedtext - >> >> >> >>> - 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. >> >> >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. You never *do* anything. And when I don't have convincing evidence, I experiment and collect some. A mouse isn't a soldering iron. John
From: Bill Sloman on 5 Jun 2010 18:00 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 and then post the results of your experiment that shows 67dB. You've got a lab full of expensive equipment - if we are to take your boasting seriously - and boast like a lion about your "insanely good" electronic designs, but then post a result that might qualify you as a mouse in an undemanding environment. Somebody with your experience ought to be aware that if you want 140dB of attenuation you are going to need more than a single stage of filtering - stray impedances usually make it difficult to get more than 60dB in a single stage. -- Bill Sloman, Nijmegen
From: John Larkin on 5 Jun 2010 18:52
On Sat, 5 Jun 2010 15:00:09 -0700 (PDT), Bill Sloman <bill.sloman(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? 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. and then post the results >of your experiment that shows 67dB. You've got a lab full of expensive >equipment - if we are to take your boasting seriously - and boast like >a lion about your "insanely good" electronic designs, but then post a >result that might qualify you as a mouse in an undemanding >environment. This is the sort of thing you could do. It doesn't take expensive equipment to measure, say, 80 or 100 dB of ripple rejection. Just a little thought and patience. So try it - for real - and we'll compare numbers. If not for money, just to keep your mind from rotting. > >Somebody with your experience ought to be aware that if you want 140dB >of attenuation you are going to need more than a single stage of >filtering - stray impedances usually make it difficult to get more >than 60dB in a single stage. My experience was entirely inadequate to make such a pronouncement. I did some tests. Now I know more than I did before. You don't approve? John |