Forums

2N4261 modern days replacement

Started by Sergey Kubushyn June 26, 2013
Frank Miles <fpm@u.washington.edu> wrote:
> On Mon, 01 Jul 2013 22:26:20 +0000, Sergey Kubushyn wrote: > >> Wimpie <wimabctel@tetech.nl> wrote: >>> El 01-07-13 5:42, Sergey Kubushyn escribi&oacute;: >>>> josephkk<joseph_barrett@sbcglobal.net> wrote: >>>>> On Sun, 30 Jun 2013 03:44:03 +0000 (UTC), Sergey >>>>> Kubushyn<ksi@koi8.net> wrote: >>>>> >>>>>> josephkk<joseph_barrett@sbcglobal.net> wrote: >>>>>>> On Wed, 26 Jun 2013 19:48:07 +0000 (UTC), Sergey >>>>>>> Kubushyn<ksi@koi8.net> wrote: >>>>>>> >>>>>>>> Can anybody point to something available now to replace 2N4261 >>>>>>>> transistor? It will be used in its primary role, as fast switcher. >>>>>>>> >>>>>>> The device actually seems to actually be available (arrow) in to72 >>>>>>> package made by microsemi and semicoa (albeit only in expensive >>>>>>> military grades). Doesn't seem all that special from the data >>>>>>> sheets i found. >>>>>> >>>>>> It is "available" but they have none in stock. You can definitely >>>>>> place an order with them for a box or more and eventually you might >>>>>> even get it in a year or so. >>>>>> >>>>>> The only real guys who do have those in stock are Freelance >>>>>> Electronics. BTW, highly recommended -- they have lots of obsolete >>>>>> and rare parts and those are really in stock so you get actual price >>>>>> right away and can purchase them online and get them shipped next >>>>>> business day. Not like all those sellers of hot air (and now many of >>>>>> them even show up on Octopart) that you have to ask for a quote, >>>>>> give them your target price and they might start looking for those >>>>>> parts usually coming out empty. >>>>>> >>>>>> Quest has 3 (three) in stock, Freelance has more (100+) but those >>>>>> are pretty expensive. I would like to buy something like 50 of those >>>>>> but not going to do this for $10 a pop... >>>>>> >>>>>> As for not being all that special -- such an expression usually >>>>>> means there are many similar parts around so one can just use >>>>>> something else. So if they are not all that special please point me >>>>>> to those similar transistors and I will happily purchase those >>>>>> instead. >>>>>> >>>>>> The closest one I'm aware of is BSR12. It works just fine in place >>>>>> of e.g. 2N4258 that is also used in many older Tek instruments but >>>>>> 2N4261 is at least 5 times faster and I can not find anything that >>>>>> would've matched its speed among modern transistors. If you know >>>>>> something suitable please tell what it is. >>>>> >>>>> Well a quick bit of hunting brought up BFT92 and BFQ75 both in >>>>> surface mount packages. Both of have higher ft though. >>>> >>>> BFQ75 is even a bigger rarity than 2N4261. BFT92 I do know and was >>>> going to give those a try but they are NOT switching transistors. They >>>> MIGHT work OK for fast saturating switching but that is not guaranteed >>>> -- nobody tested them in such applications and high Ft does not >>>> guarantee they would be as good switchers as they are amplifiers. >>> >>> Is it really used as a saturated switch? The test circuit below the >>> switching time graphs of an old Motorola datasheet (can be found on the >>> web) shows a long-tailed pair. This suggest non-saturated switching >>> times. >>> >>> If it is used as saturated switch, is it really that fast as shown in >>> some short-form datasheets? All short form datasheets don't show the >>> reverse base current for measuring turn-off time. >> >> Look at Semicoa or Microsemi datasheets. They clearly say "Saturated >> Turn On Switching Time to 90%" and off to 10% (Vcc = 17V, 50 ohm pulse >> generator). >> >> And yes, it is used as saturated switch. >> >> I can not find that old Motorola datasheet. I can only find various >> Semicoa/Microsemi datasheets (some shorter, some more complete) and one >> really old from New Jersey Semiconductor Products, Inc. dated June 1973. >> I confess to not digging past Google 5th page but it is mostly junk >> "sellers" ready to sell you any part, even one that never existed. > > There's a 3-page datasheet in the Moto "Small Signal Semiconductors" (C) 1987, starting > on page 4-172. My copy has some obvious printing defects, but definitely > gives turn-on and turn-off delays.
Unfortunately Google won't find your copy :) I do not have a paper catalog so I'm limited to only what I can find on the Net... BTW, it is a good idea to start looking for a paper catalog. It might be extremely handy for older equipment repair 'coz many of those older semiconductors never made it to the Net... --- ****************************************************************** * KSI@home KOI8 Net < > The impossible we do immediately. * * Las Vegas NV, USA < > Miracles require 24-hour notice. * ******************************************************************
Le Mon, 01 Jul 2013 23:38:39 +0000, Sergey Kubushyn a &eacute;crit:

> Frank Miles <fpm@u.washington.edu> wrote: >> On Mon, 01 Jul 2013 22:26:20 +0000, Sergey Kubushyn wrote: >> >>> Wimpie <wimabctel@tetech.nl> wrote: >>>> El 01-07-13 5:42, Sergey Kubushyn escribi&oacute;: >>>>> josephkk<joseph_barrett@sbcglobal.net> wrote: >>>>>> On Sun, 30 Jun 2013 03:44:03 +0000 (UTC), Sergey >>>>>> Kubushyn<ksi@koi8.net> wrote: >>>>>> >>>>>>> josephkk<joseph_barrett@sbcglobal.net> wrote: >>>>>>>> On Wed, 26 Jun 2013 19:48:07 +0000 (UTC), Sergey >>>>>>>> Kubushyn<ksi@koi8.net> wrote: >>>>>>>> >>>>>>>>> Can anybody point to something available now to replace 2N4261 >>>>>>>>> transistor? It will be used in its primary role, as fast >>>>>>>>> switcher. >>>>>>>>> >>>>>>>> The device actually seems to actually be available (arrow) in >>>>>>>> to72 package made by microsemi and semicoa (albeit only in >>>>>>>> expensive military grades). Doesn't seem all that special from >>>>>>>> the data sheets i found. >>>>>>> >>>>>>> It is "available" but they have none in stock. You can definitely >>>>>>> place an order with them for a box or more and eventually you >>>>>>> might even get it in a year or so. >>>>>>> >>>>>>> The only real guys who do have those in stock are Freelance >>>>>>> Electronics. BTW, highly recommended -- they have lots of obsolete >>>>>>> and rare parts and those are really in stock so you get actual >>>>>>> price right away and can purchase them online and get them shipped >>>>>>> next business day. Not like all those sellers of hot air (and now >>>>>>> many of them even show up on Octopart) that you have to ask for a >>>>>>> quote, give them your target price and they might start looking >>>>>>> for those parts usually coming out empty. >>>>>>> >>>>>>> Quest has 3 (three) in stock, Freelance has more (100+) but those >>>>>>> are pretty expensive. I would like to buy something like 50 of >>>>>>> those but not going to do this for $10 a pop... >>>>>>> >>>>>>> As for not being all that special -- such an expression usually >>>>>>> means there are many similar parts around so one can just use >>>>>>> something else. So if they are not all that special please point >>>>>>> me to those similar transistors and I will happily purchase those >>>>>>> instead. >>>>>>> >>>>>>> The closest one I'm aware of is BSR12. It works just fine in place >>>>>>> of e.g. 2N4258 that is also used in many older Tek instruments but >>>>>>> 2N4261 is at least 5 times faster and I can not find anything that >>>>>>> would've matched its speed among modern transistors. If you know >>>>>>> something suitable please tell what it is. >>>>>> >>>>>> Well a quick bit of hunting brought up BFT92 and BFQ75 both in >>>>>> surface mount packages. Both of have higher ft though. >>>>> >>>>> BFQ75 is even a bigger rarity than 2N4261. BFT92 I do know and was >>>>> going to give those a try but they are NOT switching transistors. >>>>> They MIGHT work OK for fast saturating switching but that is not >>>>> guaranteed -- nobody tested them in such applications and high Ft >>>>> does not guarantee they would be as good switchers as they are >>>>> amplifiers. >>>> >>>> Is it really used as a saturated switch? The test circuit below the >>>> switching time graphs of an old Motorola datasheet (can be found on >>>> the web) shows a long-tailed pair. This suggest non-saturated >>>> switching times. >>>> >>>> If it is used as saturated switch, is it really that fast as shown in >>>> some short-form datasheets? All short form datasheets don't show >>>> the reverse base current for measuring turn-off time. >>> >>> Look at Semicoa or Microsemi datasheets. They clearly say "Saturated >>> Turn On Switching Time to 90%" and off to 10% (Vcc = 17V, 50 ohm pulse >>> generator). >>> >>> And yes, it is used as saturated switch. >>> >>> I can not find that old Motorola datasheet. I can only find various >>> Semicoa/Microsemi datasheets (some shorter, some more complete) and >>> one really old from New Jersey Semiconductor Products, Inc. dated June >>> 1973. >>> I confess to not digging past Google 5th page but it is mostly junk >>> "sellers" ready to sell you any part, even one that never existed. >> >> There's a 3-page datasheet in the Moto "Small Signal Semiconductors" >> (C) 1987, starting on page 4-172. My copy has some obvious printing >> defects, but definitely gives turn-on and turn-off delays. > > Unfortunately Google won't find your copy :) I do not have a paper > catalog so I'm limited to only what I can find on the Net... > > BTW, it is a good idea to start looking for a paper catalog. It might be > extremely handy for older equipment repair 'coz many of those older > semiconductors never made it to the Net... >
Scanned and posted on ABSE... -- Thanks, Fred.
Fred Bartoli <mynamewithAdotinbetween@free.fr> wrote:
> Le Mon, 01 Jul 2013 23:38:39 +0000, Sergey Kubushyn a &eacute;crit:
[dd]
>>>>>>> Well a quick bit of hunting brought up BFT92 and BFQ75 both in >>>>>>> surface mount packages. Both of have higher ft though. >>>>>> >>>>>> BFQ75 is even a bigger rarity than 2N4261. BFT92 I do know and was >>>>>> going to give those a try but they are NOT switching transistors. >>>>>> They MIGHT work OK for fast saturating switching but that is not >>>>>> guaranteed -- nobody tested them in such applications and high Ft >>>>>> does not guarantee they would be as good switchers as they are >>>>>> amplifiers. >>>>> >>>>> Is it really used as a saturated switch? The test circuit below the >>>>> switching time graphs of an old Motorola datasheet (can be found on >>>>> the web) shows a long-tailed pair. This suggest non-saturated >>>>> switching times. >>>>> >>>>> If it is used as saturated switch, is it really that fast as shown in >>>>> some short-form datasheets? All short form datasheets don't show >>>>> the reverse base current for measuring turn-off time. >>>> >>>> Look at Semicoa or Microsemi datasheets. They clearly say "Saturated >>>> Turn On Switching Time to 90%" and off to 10% (Vcc = 17V, 50 ohm pulse >>>> generator). >>>> >>>> And yes, it is used as saturated switch. >>>> >>>> I can not find that old Motorola datasheet. I can only find various >>>> Semicoa/Microsemi datasheets (some shorter, some more complete) and >>>> one really old from New Jersey Semiconductor Products, Inc. dated June >>>> 1973. >>>> I confess to not digging past Google 5th page but it is mostly junk >>>> "sellers" ready to sell you any part, even one that never existed. >>> >>> There's a 3-page datasheet in the Moto "Small Signal Semiconductors" >>> (C) 1987, starting on page 4-172. My copy has some obvious printing >>> defects, but definitely gives turn-on and turn-off delays. >> >> Unfortunately Google won't find your copy :) I do not have a paper >> catalog so I'm limited to only what I can find on the Net... >> >> BTW, it is a good idea to start looking for a paper catalog. It might be >> extremely handy for older equipment repair 'coz many of those older >> semiconductors never made it to the Net... >> > > Scanned and posted on ABSE...
Too late :) I've already bought my own copy of "Small Signal Semiconductors" so I will be able to see the original once it hit my door... --- ****************************************************************** * KSI@home KOI8 Net < > The impossible we do immediately. * * Las Vegas NV, USA < > Miracles require 24-hour notice. * ******************************************************************
El 02-07-13 0:26, Sergey Kubushyn escribi&oacute;:
> Wimpie<wimabctel@tetech.nl> wrote: >> El 01-07-13 5:42, Sergey Kubushyn escribi&oacute;: >>> josephkk<joseph_barrett@sbcglobal.net> wrote: >>>> On Sun, 30 Jun 2013 03:44:03 +0000 (UTC), Sergey Kubushyn<ksi@koi8.net> >>>> wrote: >>>> >>>>> josephkk<joseph_barrett@sbcglobal.net> wrote: >>>>>> On Wed, 26 Jun 2013 19:48:07 +0000 (UTC), Sergey Kubushyn<ksi@koi8.net> >>>>>> wrote: >>>>>> >>>>>>> Can anybody point to something available now to replace 2N4261 transistor? >>>>>>> It will be used in its primary role, as fast switcher. >>>>>>> >>>>>> The device actually seems to actually be available (arrow) in to72 package >>>>>> made by microsemi and semicoa (albeit only in expensive military grades). >>>>>> Doesn't seem all that special from the data sheets i found. >>>>> >>>>> It is "available" but they have none in stock. You can definitely place an >>>>> order with them for a box or more and eventually you might even get it in a >>>>> year or so. >>>>> >>>>> The only real guys who do have those in stock are Freelance Electronics. >>>>> BTW, highly recommended -- they have lots of obsolete and rare parts and >>>>> those are really in stock so you get actual price right away and can >>>>> purchase them online and get them shipped next business day. Not like all >>>>> those sellers of hot air (and now many of them even show up on Octopart) >>>>> that you have to ask for a quote, give them your target price and they might >>>>> start looking for those parts usually coming out empty. >>>>> >>>>> Quest has 3 (three) in stock, Freelance has more (100+) but those are pretty >>>>> expensive. I would like to buy something like 50 of those but not going to >>>>> do this for $10 a pop... >>>>> >>>>> As for not being all that special -- such an expression usually means there >>>>> are many similar parts around so one can just use something else. So if they >>>>> are not all that special please point me to those similar transistors and I >>>>> will happily purchase those instead. >>>>> >>>>> The closest one I'm aware of is BSR12. It works just fine in place of e.g. >>>>> 2N4258 that is also used in many older Tek instruments but 2N4261 is at >>>>> least 5 times faster and I can not find anything that would've matched its >>>>> speed among modern transistors. If you know something suitable please tell >>>>> what it is. >>>> >>>> Well a quick bit of hunting brought up BFT92 and BFQ75 both in surface >>>> mount packages. Both of have higher ft though. >>> >>> BFQ75 is even a bigger rarity than 2N4261. BFT92 I do know and was going to >>> give those a try but they are NOT switching transistors. They MIGHT work OK >>> for fast saturating switching but that is not guaranteed -- nobody tested >>> them in such applications and high Ft does not guarantee they would be as >>> good switchers as they are amplifiers. >> >> Is it really used as a saturated switch? The test circuit below the >> switching time graphs of an old Motorola datasheet (can be found on >> the web) shows a long-tailed pair. This suggest non-saturated >> switching times. >> >> If it is used as saturated switch, is it really that fast as shown in >> some short-form datasheets? All short form datasheets don't show the >> reverse base current for measuring turn-off time. > > Look at Semicoa or Microsemi datasheets. They clearly say "Saturated Turn On > Switching Time to 90%" and off to 10% (Vcc = 17V, 50 ohm pulse generator). > > And yes, it is used as saturated switch. > > I can not find that old Motorola datasheet. I can only find various > Semicoa/Microsemi datasheets (some shorter, some more complete) and one > really old from New Jersey Semiconductor Products, Inc. dated June 1973. I > confess to not digging past Google 5th page but it is mostly junk "sellers" > ready to sell you any part, even one that never existed. > > --- > ****************************************************************** > * KSI@home KOI8 Net< > The impossible we do immediately. * > * Las Vegas NV, USA< > Miracles require 24-hour notice. * > ******************************************************************
I know the notes on saturated switching on the short form data sheets without any details. The old motorola sheet shows a long-tailed pair and then it becomes suspicious. I mailed you the Motorola datasheet showing the long-tailed pair. When I look to the circuit and component values mentioned, the transistor doesn't go into saturation. -- Wim PA3DJS www.tetech.nl Please remove abc first in case of PM