Unusual functions of cheap parts
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From: dagmargoodboat on 30 Nov 2005 17:32 Jim Thompson wrote: > On Sat, 26 Nov 2005 21:41:06 +0100, Winfried Salomon > <wsalomontrashcan(a)t-online.de> wrote: > > >Hello Jorgen, > > > >Jorgen Lund-Nielsen wrote: > > > >[.....] > >> 2N2369 for fast pulses. > > > >btw, do you know a standard complementary pnp-transistor for the 2N2369, > >such like 2N3905 but with higher ft and less feedback capacitance? It > >seems that the manufactorers have almost no data on their internet pages. > > > >mfg. Winfried > > A 2N2369 is a gold-doped NPN, gold-doped to kill storage time and > improve recovery from saturation. I don't recall any PNP device with > gold-doping... or the equivalent. > > ...Jim Thompson National Semi's (now Fairchild) 2n5771 was a gold-doped PNP. ft>=850MHz. For avalanche mode one might try the lower-Vce-rated PN3640 (12v), or PN3639 (6v). I might even have notes on this. I tested/compared various BJTs in avalanche mode some years ago, trying to find the "best." ISTR picking the 2n2369, both because it was fast, and because it avalanched reliably where other types wouldn't. James Arthur
From: John Larkin on 30 Nov 2005 17:45 On 30 Nov 2005 14:32:29 -0800, dagmargoodboat(a)yahoo.com wrote: > >Jim Thompson wrote: >> On Sat, 26 Nov 2005 21:41:06 +0100, Winfried Salomon >> <wsalomontrashcan(a)t-online.de> wrote: >> >> >Hello Jorgen, >> > >> >Jorgen Lund-Nielsen wrote: >> > >> >[.....] >> >> 2N2369 for fast pulses. >> > >> >btw, do you know a standard complementary pnp-transistor for the 2N2369, >> >such like 2N3905 but with higher ft and less feedback capacitance? It >> >seems that the manufactorers have almost no data on their internet pages. >> > >> >mfg. Winfried >> >> A 2N2369 is a gold-doped NPN, gold-doped to kill storage time and >> improve recovery from saturation. I don't recall any PNP device with >> gold-doping... or the equivalent. >> >> ...Jim Thompson > > National Semi's (now Fairchild) 2n5771 was a gold-doped PNP. >ft>=850MHz. For avalanche mode one might try the lower-Vce-rated >PN3640 (12v), or PN3639 (6v). > > I might even have notes on this. I tested/compared various BJTs in >avalanche mode some years ago, trying to find the "best." ISTR picking >the 2n2369, both because it was fast, and because it avalanched >reliably where other types wouldn't. > > James Arthur Hi, James, Interestingly, the best avalanchers aren't usually super-fast transistors, but old klunky things. The Zetex avalanche transistors have lowish Ft's and are made in Russia, maybe on an old process. John
From: dagmargoodboat on 30 Nov 2005 18:53 John Larkin wrote: > On 30 Nov 2005 14:32:29 -0800, dagmargoodboat(a)yahoo.com wrote: > > > > >Jim Thompson wrote: <snip quote> > >> A 2N2369 is a gold-doped NPN, gold-doped to kill storage time and > >> improve recovery from saturation. I don't recall any PNP device with > >> gold-doping... or the equivalent. > >> > >> ...Jim Thompson > > > > National Semi's (now Fairchild) 2n5771 was a gold-doped PNP. > >ft>=850MHz. For avalanche mode one might try the lower-Vce-rated > >PN3640 (12v), or PN3639 (6v). > > > > I might even have notes on this. I tested/compared various BJTs in > >avalanche mode some years ago, trying to find the "best." ISTR picking > >the 2n2369, both because it was fast, and because it avalanched > >reliably where other types wouldn't. > > > > James Arthur > > > Hi, James, > > Interestingly, the best avalanchers aren't usually super-fast > transistors, but old klunky things. The Zetex avalanche transistors > have lowish Ft's and are made in Russia, maybe on an old process. > > John Howdy John, I was unclear: by "...it was fast..." I meant the 2n2369 was one of the devices with the fastest avalanche edges. Digging through some of my notes, I don't see the BJT comparison, but a 2n2222 biased to +100Vce, banged / triggered by a 74HC-series gate, gave synchronous 750pS risetime pulses. Not very impressive, really, though good for higher-power stuff than I needed. Interestingly, I found a 74AC00 driving an MPS2369 was faster & less trouble: 360pS fall (turn on) time, & 570pS rise (turn off) time, and no nasty high voltage supplies. It was possibly even a little faster than measured--at 360pS I was pushing my poor little 7S14 1-GHz sampling plug-in pretty hard. Best, James
From: Scott Newell on 30 Nov 2005 19:37 John Larkin wrote: > > Interestingly, the best avalanchers aren't usually super-fast > transistors, but old klunky things. The Zetex avalanche transistors > have lowish Ft's and are made in Russia, maybe on an old process. Is there a known figure of merit that would help select devices types for fast avalanche breakdown? -- newell
From: Winfield Hill on 30 Nov 2005 21:46
Winfried Salomon wrote... > Jorgen Lund-Nielsen wrote: >> Winfried Salomon wrote: >> >>> btw, do you know a standard complementary pnp-transistor for the >>> 2N2369, such like 2N3905 but with higher ft and less feedback >>> capacitance? It seems that the manufactorers have almost no data >>> on their internet pages. >> >> Maybe 2N4261? Have not looked into the datasheet, but as i remember, >> i have seen them sometimes in complementary with the 2N2369 That was a high-frequency part for the time, spec'd at 1200MHz... > the problem is, that it is an rf-transistor and can't be driven at > 30V/0.2A, I found a complementary in an old table KTT, the 2N2894A, > but it also has max. 12V, so I find no other than the 2N3906. An old Raytheon datasheet says the 2N2894 was doped with platinum. BTW -- in AoE, we list the 2n5771 as a PNP complement to the NPN 2n5769, both 15V plastic versions of older metal-can parts. -- Thanks, - Win |