Rectify 500MHz Small Signal
in [Design]
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From: Nico Coesel on 30 Sep 2009 12:29 John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Tue, 29 Sep 2009 12:53:36 -0700, Joerg <invalid(a)invalid.invalid> >wrote: > > >There are some little USB samplers, but they're very expensive. What amount do you consider expensive? -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... "If it doesn't fit, use a bigger hammer!" --------------------------------------------------------------
From: John Larkin on 30 Sep 2009 13:15 On Wed, 30 Sep 2009 16:29:03 GMT, nico(a)puntnl.niks (Nico Coesel) wrote: >John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Tue, 29 Sep 2009 12:53:36 -0700, Joerg <invalid(a)invalid.invalid> >>wrote: >> >> >>There are some little USB samplers, but they're very expensive. > >What amount do you consider expensive? $12K is expensive. John
From: Joerg on 30 Sep 2009 13:24 John Larkin wrote: > On Tue, 29 Sep 2009 15:27:53 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: >>> On Tue, 29 Sep 2009 12:53:36 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> John Larkin wrote: >>>>> On Tue, 29 Sep 2009 13:34:14 -0400, Phil Hobbs >>>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>>>> >>>>>> John Larkin wrote: >>>>>>> On Tue, 29 Sep 2009 09:25:15 -0700, Joerg <invalid(a)invalid.invalid> >>>>>>> wrote: >>>>>>> >>>>>>>> John Larkin wrote: >>>>>>>>> On Mon, 28 Sep 2009 17:43:22 -0700, Joerg <invalid(a)invalid.invalid> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>>>> John Larkin wrote: >>>>>>>>>>> On Mon, 28 Sep 2009 20:05:23 -0400, Phil Hobbs >>>>>>>>>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>>>>>>>>>> >>>>>>>>>>>> John Fields wrote: >>>>>>>>>>>>> On Mon, 28 Sep 2009 10:25:05 -0700, John Larkin >>>>>>>>>>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>>>>>>>>>> >>>>>>>>>>>>>> On Sat, 26 Sep 2009 17:58:27 -0700, Archimedes' Lever >>>>>>>>>>>>>> <OneBigLever(a)InfiniteSeries.Org> wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>>> On Sat, 26 Sep 2009 16:52:40 -0700, John Larkin >>>>>>>>>>>>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> On Sat, 26 Sep 2009 17:28:50 -0400, "Michael A. Terrell" >>>>>>>>>>>>>>>> <mike.terrell(a)earthlink.net> wrote: >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> John Larkin wrote: >>>>>>>>>>>>>>>>>> There's the slideback technique: drive a comparator with RF on one >>>>>>>>>>>>>>>>>> side, DC feedback on the other. Tease the DC appropriately. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> I once made a slideback sampling oscilloscope, using tunnel diodes, as >>>>>>>>>>>>>>>>>> my EE senior project. I won an award and had to attend a dreadful IEEE >>>>>>>>>>>>>>>>>> chapter banquet and repeat it to a bunch of old-fart power engineers >>>>>>>>>>>>>>>>>> who didn't understand a word I said. I described the slideback >>>>>>>>>>>>>>>>>> sampling scope in this ng some years back and a certain party loved >>>>>>>>>>>>>>>>>> the idea so much he later decided that he'd invented it himself. >>>>>>>>>>>>>>>>> <http://store.americanmicrosemiconductor.com/diodes-tunnel-diodes.html> >>>>>>>>>>>>>>>> TDs are insanely expensive nowadays, ballpark $100. I used to get them >>>>>>>>>>>>>>>> for a couple bucks from Allied. The fabrication process is insane, and >>>>>>>>>>>>>>>> nobody ever modernized it. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> There are some more modern planar germanium back diodes, essentially >>>>>>>>>>>>>>>> low Ip tunnel diodes, but they're RF detectors, useless for switching. >>>>>>>>>>>>>>>> Pity, I used to like tunnel diodes. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> http://aeroflex.com/AMS/Metelics/pdfiles/MBD_Series_Planar_Back_Tunnel_Diodes.pdf >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> John >>>>>>>>>>>>>>> Try PiN diodes then. >>>>>>>>>>>>>> For what? Certainly not switching, amplifying, oscillating, detection, >>>>>>>>>>>>>> or mixing. >>>>>>>>>>>>> --- >>>>>>>>>>>>> Re. switching, From: >>>>>>>>>>>>> >>>>>>>>>>>>> http://en.wikipedia.org/wiki/PIN_diode >>>>>>>>>>>>> >>>>>>>>>>>>> "Under zero or reverse bias, a PIN diode has a low capacitance. The low >>>>>>>>>>>>> capacitance will not pass much of an RF signal. Under a forward bias of >>>>>>>>>>>>> 1 mA, a typical PIN diode will have an RF resistance of about 1 ohm, >>>>>>>>>>>>> making it a good RF conductor. Consequently, the PIN diode makes a good >>>>>>>>>>>>> RF switch." >>>>>>>>>>>>> --- >>>>>>>>>>>> Good, but not fast. PIN diodes specialize in having a lot of stored >>>>>>>>>>>> charge, so that the signal current can be quite a bit larger than the DC >>>>>>>>>>>> current without causing excessive distortion. >>>>>>>>>>>> >>>>>>>>>>>> Cheers >>>>>>>>>>>> >>>>>>>>>>>> Phil Hobbs >>>>>>>>>>> PINs stop behaving like PINs at low frequencies, too. So they don't >>>>>>>>>>> make useful wideband switches. >>>>>>>>>>> >>>>>>>>>> Got to watch the carrier lifetime. The lower the bottom of your spectrum >>>>>>>>>> and the higher the RF current, the longer its carrier lifetime must be. >>>>>>>>>> I found PIN diodes to be great and most of all cheap variable >>>>>>>>>> attenuators as well as switched. Designed in tons of them. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>>> But I meant active switching when I was referring to a TD. A TD would >>>>>>>>>>> *generate* a fast step from an arbitrarily slow drive. >>>>>>>>>>> >>>>>>>>>> I've drooled over SRDs all my life and every time I wanted to buy one I >>>>>>>>>> either couldn't have one or it was outlandishly expensive. Guess >>>>>>>>>> avalanching is the only game in town and if you want avalanche-rated >>>>>>>>>> then a bone-simple BJT can easily shoot up to twenty bucks. >>>>>>>>> SRDs aren't hard to get. MA/Com has distributor parts, under a buck. >>>>>>>>> M-Pulse and Metelics are good about samples. If you want a few, send >>>>>>>>> me a SASE. >>>>>>>>> >>>>>>>>> Oh, here it is... >>>>>>>>> >>>>>>>>> 229-1769 DIO SRD 30V SOT23 150PS MA44769 1PF >>>>>>>>> >>>>>>>>> MA44769-287 PENSTOCK >>>>>>>>> >>>>>>>>> Price 58 cents in small quantities. >>>>>>>>> >>>>>>>>> They also have MA44767-287, 600 ps risetime, a little easier to drive >>>>>>>>> because it stores more charge. >>>>>>>>> >>>>>>>>> These make nice edge generators and frequency multipliers. I have a >>>>>>>>> rubidium clock that generates the 6.3846826128 GHz frequency from a 10 >>>>>>>>> MHz rock with an absurdly small number of cheap parts. >>>>>>>>> >>>>>>>> Thanks, John! That's a decent price. And thanks for the SASE offer, but >>>>>>>> maybe I'll combine that with a beer at Zeitgeist when I get down there :-) >>>>>>> Well, drop in. We have a zillion exotic parts in stock. And the >>>>>>> quality of Z's burgers has improved radically lately. Only biker bar I >>>>>>> know of with Chimay on tap. >>>>>>> >>>>>>>> As a kid I grew up in Europe and back then such exotic parts were very >>>>>>>> hard to find over there, even at hamfests. >>>>>>> We were lucky. Tons of exotic surplus gear, lots of old teevees, >>>>>>> Allied and Lafayette and Fair Radio Sales mail-order available to >>>>>>> anyone, local distributors for over-the-counter transistors and >>>>>>> 10-turn pots and such... the counter guys gave me more parts than I >>>>>>> ever paid for. I made a deal with my parents to dump my allowance in >>>>>>> favor of a revolving credit account with Allied, so I could just order >>>>>>> stuff. I made spending money fixing radios and TVs. >>>>>>> >>>>>>> John >>>>>>> >>>>>> Still not as good as now. I just bought an excellent-condition HP 8568B >>>>>> spectrum analyzer for $900. About 2 cents on the dollar. So far this >>>>>> year I've bought test equipment that would have cost way over $100000 >>>>>> new, for probably $4k altogether. Amazing. >>>>>> >>>>>> Cheers >>>>>> >>>>>> Phil Hobbs >>>>> And I'm looking at, theoretically, a quarter million dollars worth of >>>>> sampling heads over there on my shelf. This is an amazing time to >>>>> start a niche business, or even an exotic hobby. >>>>> >>>> Is there anything available at reasonable cost that does zippy sampling >>>> without needing a Goliath of a scope attached to it? >>> Not really. The 5000 and 7000 series scopes had sampling plugins - I >>> have a bunch, and they're dirt cheap now - but they were pretty bad >>> compared to the superb 11801-series stuff. >>> >> There is an 11802 on Ebay right now for $1k but untested, "powers up". >> Thing is, I haven't gotten much more space here. A sampler for the 7704 >> over here would be nice. What is so bad with S-4 and 7S11? Ok, the >> 25psec risetime doesn't quite rival your gear but for most stuff that >> should do. > > That stuff works, but it's not as quantitative as the later gear. And > TDR is a fabulous thing to have, and the TDR on the 7-series stuff is > really mediocre. > > Isn't this beautiful? > > ftp://jjlarkin.lmi.net/Z250A.jpg > ftp://jjlarkin.lmi.net/Z250_TDR.jpg > > (TDR of the test trace, J28 to J29) > That is indeed beautiful. Although, to be honest, I never really had an urgent need for TDR. Occasionally I resonate stuff out with a <gasp> dip meter. But even there it has happened that I didn't use for a while and the battery oozed out. I also have this as a backup: http://oak.cats.ohiou.edu/~postr/bapix/Dip_59.htm Knock on wood that the tubes don't go out on me. Of course, when things resonate above 400MHz I am up the creek unless I kludge something. >> >>> There are some little USB samplers, but they're very expensive. >>> >> Probably not much of a market anymore and the TDR guys in the field >> dont' need a precision under a foot to figure where they have to drop >> the bucket of their Kubota. > > Too much cheap surplus stuff on ebay, too. I'd love to do a cheapish > USB TDR, but there's probably no good market. > There probably isn't much of a TDR market. But I believe there would be a market for a sampling scope app where people can check (repetitive) timings to within several picoseconds. With comm data rates almost in the two-digit GHz-range that market should be growing. Of course it would need to beat the surplus stuff in price or at least be on par. The added benefit is the easy documentation via mouse click. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 30 Sep 2009 13:32 John Larkin wrote: > On Wed, 30 Sep 2009 16:29:03 GMT, nico(a)puntnl.niks (Nico Coesel) > wrote: > >> John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>> On Tue, 29 Sep 2009 12:53:36 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>> >>> There are some little USB samplers, but they're very expensive. >> What amount do you consider expensive? > > $12K is expensive. > Yes. I the US one can buy a fairly decent passenger car for that kind of money. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 30 Sep 2009 13:53
On Wed, 30 Sep 2009 10:24:56 -0700, Joerg <invalid(a)invalid.invalid> wrote: >> >> That stuff works, but it's not as quantitative as the later gear. And >> TDR is a fabulous thing to have, and the TDR on the 7-series stuff is >> really mediocre. >> >> Isn't this beautiful? >> >> ftp://jjlarkin.lmi.net/Z250A.jpg >> ftp://jjlarkin.lmi.net/Z250_TDR.jpg >> >> (TDR of the test trace, J28 to J29) >> > >That is indeed beautiful. Although, to be honest, I never really had an >urgent need for TDR. Occasionally I resonate stuff out with a <gasp> dip >meter. But even there it has happened that I didn't use for a while and >the battery oozed out. I also have this as a backup: > >http://oak.cats.ohiou.edu/~postr/bapix/Dip_59.htm > >Knock on wood that the tubes don't go out on me. Of course, when things >resonate above 400MHz I am up the creek unless I kludge something. Trace impedances matter a lot to us. Board houses sometimes take liberties with multilayer stackups and copper thickness, so we try to build in test traces for both impedance and resistance when it matters. That test trace in the pics takes a tour of all 4 board layers, so we can see all the impedances. It's even more fun on 8-layer boards. It's a good check for our math, too. It's also cool to add SMAs to access power pour layers and TDR them. That blows away all sorts of cockeyed theories about bypassing high-speed stuff. Transitions, like pcb-to-connector, are also interesting to TDR. Leads to x-acto slashing sometimes. > >>> >>>> There are some little USB samplers, but they're very expensive. >>>> >>> Probably not much of a market anymore and the TDR guys in the field >>> dont' need a precision under a foot to figure where they have to drop >>> the bucket of their Kubota. >> >> Too much cheap surplus stuff on ebay, too. I'd love to do a cheapish >> USB TDR, but there's probably no good market. >> > >There probably isn't much of a TDR market. But I believe there would be >a market for a sampling scope app where people can check (repetitive) >timings to within several picoseconds. With comm data rates almost in >the two-digit GHz-range that market should be growing. One market for a small, affordable USB TDR would be to sell to board houses. The Polar Instruments stuff (from the Channel Islands, another story) is expensive and very dated. John |