Rectify 500MHz Small Signal
in [Design]
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From: Joerg on 28 Sep 2009 20:46 John Larkin wrote: [...] > But I meant active switching when I was referring to a TD. A TD would > *generate* a fast step from an arbitrarily slow drive. > Forgot to mention, I was also never able to lay my hand on a tunnel diode. The hobbyist books had schematics with them in there but that was all bogus, just like UJTs were. Unobtanium. Can you buy a TD in large qties at a reasonable price somewhere? I mean, not the $100 ones. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Archimedes' Lever on 28 Sep 2009 20:51 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 We use them at 10GHz bands. Or maybe it is only used with a trap filter.
From: Mycelium on 28 Sep 2009 20:55 On Mon, 28 Sep 2009 17:46:39 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: > >[...] > >> But I meant active switching when I was referring to a TD. A TD would >> *generate* a fast step from an arbitrarily slow drive. >> > >Forgot to mention, I was also never able to lay my hand on a tunnel >diode. The hobbyist books had schematics with them in there but that was >all bogus, just like UJTs were. Unobtanium. Can you buy a TD in large >qties at a reasonable price somewhere? I mean, not the $100 ones. Old radios (transceivers).
From: Joerg on 28 Sep 2009 20:58 Mycelium wrote: > On Mon, 28 Sep 2009 17:46:39 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: >> >> [...] >> >>> But I meant active switching when I was referring to a TD. A TD would >>> *generate* a fast step from an arbitrarily slow drive. >>> >> Forgot to mention, I was also never able to lay my hand on a tunnel >> diode. The hobbyist books had schematics with them in there but that was >> all bogus, just like UJTs were. Unobtanium. Can you buy a TD in large >> qties at a reasonable price somewhere? I mean, not the $100 ones. > > > Old radios (transceivers). When I was a kid I repaired a lot of transceivers. None had TDs in there. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 28 Sep 2009 21:34
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. John |