Has anyone seen a NPN bipolar transistor with emitter in the middle, tab. Emitter is easier to ground in RF amplifiers.
A SOT-89 with emitter in the middle
Started by ●December 21, 2017
Reply by ●December 21, 20172017-12-21
Am 21.12.2017 um 21:07 schrieb LM:> Has anyone seen a NPN bipolar transistor with emitter in the middle, > tab. Emitter is easier to ground in RF amplifiers. >Yes. Infineon BFQ790. regards, Gerhard
Reply by ●December 21, 20172017-12-21
On Thu, 21 Dec 2017 21:55:23 +0100, Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> wrote:>Am 21.12.2017 um 21:07 schrieb LM: >> Has anyone seen a NPN bipolar transistor with emitter in the middle, >> tab. Emitter is easier to ground in RF amplifiers. >> > >Yes. > >Infineon BFQ790. > >regards, Gerhard >Good. Digikey has it. Then read long "Absolute Maximum Ratings" list and began to wonder. BFQ790 is a bit delicate and too fast for my applicationas as <1GHZ amplifier
Reply by ●December 21, 20172017-12-21
Gerhard Hoffmann wrote...> > Am 21.12.2017 um 21:07 schrieb LM: >> Has anyone seen a NPN bipolar transistor with emitter in >> the middle, tab. Emitter is easier to ground in RF amplifiers. > > Yes. > Infineon BFQ790.And Mini-Circuits wideband RF amplifiers, that come in 3-pin SOT-89 packages, with an inductor to the supply bus, 50-ohm IN and 50-ohm OUT, have their tab and middle pin grounded. -- Thanks, - Win
Reply by ●December 21, 20172017-12-21
On Thu, 21 Dec 2017 22:07:53 +0200, LM <sala.nimi@mail.com> wrote:>Has anyone seen a NPN bipolar transistor with emitter in the middle, >tab. Emitter is easier to ground in RF amplifiers.Not me. But phemts usually have the center pin/tab as source, which is really handy. The heat apparently comes out the collector of transistors but the source of phemts. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●December 22, 20172017-12-22
Am 22.12.2017 um 04:51 schrieb John Larkin:> On Thu, 21 Dec 2017 22:07:53 +0200, LM <sala.nimi@mail.com> wrote: > >> Has anyone seen a NPN bipolar transistor with emitter in the middle, >> tab. Emitter is easier to ground in RF amplifiers. > > Not me. But phemts usually have the center pin/tab as source, which is > really handy. > > The heat apparently comes out the collector of transistors but the > source of phemts.It is the substrate that naturally ends up on the tab. That's why with JFETs, it is usually the gate. The channel is in the middle between the top and bottom gate regions, and the chip thickness plays a role in the channel height, which is not so closely controlled. Hence the variation in Vgs in JFETs for the "same effect". The BFQ790 seems to be somewhat unusual with the emitter on the substrate side, without that usual +++ doped collector well that kills voltage ratings. Note the 18 V Vcb for a 20 GHz SiGe transistor. That could be interesting for large output voltage in a cascode. And in a cascode, the emitter is relatively quiet, voltage-wise. OK, the base on the tab would be even better for that. :-) It seems, they did a lot of work to characterize that thing. Much more than just abs. max. ratings and s-parameters as it is common today. cheers, Gerhard
Reply by ●December 22, 20172017-12-22
On Fri, 22 Dec 2017 10:34:12 +0100, Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> wrote:>Am 22.12.2017 um 04:51 schrieb John Larkin: >> On Thu, 21 Dec 2017 22:07:53 +0200, LM <sala.nimi@mail.com> wrote: >> >>> Has anyone seen a NPN bipolar transistor with emitter in the middle, >>> tab. Emitter is easier to ground in RF amplifiers. >> >> Not me. But phemts usually have the center pin/tab as source, which is >> really handy. >> >> The heat apparently comes out the collector of transistors but the >> source of phemts. > >It is the substrate that naturally ends up on the tab. > >That's why with JFETs, it is usually the gate. The channel is >in the middle between the top and bottom gate regions, and the >chip thickness plays a role in the channel height, which is >not so closely controlled. Hence the variation in Vgs in JFETs >for the "same effect". > >The BFQ790 seems to be somewhat unusual with the emitter on the >substrate side, without that usual +++ doped collector well that >kills voltage ratings. > >Note the 18 V Vcb for a 20 GHz SiGe transistor. That could be >interesting for large output voltage in a cascode. >And in a cascode, the emitter is relatively quiet, voltage-wise. > >OK, the base on the tab would be even better for that. :-) > >It seems, they did a lot of work to characterize that thing. >Much more than just abs. max. ratings and s-parameters as it >is common today. > >cheers, GerhardUnfortunately, SOT89 RF transistors get discontinued a lot faster than they get introduced. I designed a wonderful circuit recently, that uses BFQ149s (PNP) parts, and then they were discontinued. Bummer. We bought 11,000 to tide us over for a while, but I'm going to have to redesign eventually. NEC and NXP have killed most of their good stuff. The actual breakdown voltages on RF parts, bipolars and phemts and schottky diodes, seem to be at least twice the data sheet value. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●December 23, 20172017-12-23
On 12/22/2017 11:56 AM, John Larkin wrote:> On Fri, 22 Dec 2017 10:34:12 +0100, Gerhard Hoffmann > <ghf@hoffmann-hochfrequenz.de> wrote: > >> Am 22.12.2017 um 04:51 schrieb John Larkin: >>> On Thu, 21 Dec 2017 22:07:53 +0200, LM <sala.nimi@mail.com> wrote: >>> >>>> Has anyone seen a NPN bipolar transistor with emitter in the middle, >>>> tab. Emitter is easier to ground in RF amplifiers. >>> >>> Not me. But phemts usually have the center pin/tab as source, which is >>> really handy. >>> >>> The heat apparently comes out the collector of transistors but the >>> source of phemts. >> >> It is the substrate that naturally ends up on the tab. >> >> That's why with JFETs, it is usually the gate. The channel is >> in the middle between the top and bottom gate regions, and the >> chip thickness plays a role in the channel height, which is >> not so closely controlled. Hence the variation in Vgs in JFETs >> for the "same effect". >> >> The BFQ790 seems to be somewhat unusual with the emitter on the >> substrate side, without that usual +++ doped collector well that >> kills voltage ratings. >> >> Note the 18 V Vcb for a 20 GHz SiGe transistor. That could be >> interesting for large output voltage in a cascode. >> And in a cascode, the emitter is relatively quiet, voltage-wise. >> >> OK, the base on the tab would be even better for that. :-) >> >> It seems, they did a lot of work to characterize that thing. >> Much more than just abs. max. ratings and s-parameters as it >> is common today. >> >> cheers, Gerhard > > Unfortunately, SOT89 RF transistors get discontinued a lot faster than > they get introduced. I designed a wonderful circuit recently, that > uses BFQ149s (PNP) parts, and then they were discontinued. Bummer. We > bought 11,000 to tide us over for a while, but I'm going to have to > redesign eventually. > > NEC and NXP have killed most of their good stuff. > > The actual breakdown voltages on RF parts, bipolars and phemts and > schottky diodes, seem to be at least twice the data sheet value.Seems like they rate them for DC, expecting the AC peaks to be of that order. Not that I've designed a Class C amp using SC-70s lately. ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
Reply by ●December 23, 20172017-12-23
On 21 Dec 2017 13:54:51 -0800, Winfield Hill <hill@rowland.harvard.edu> wrote:>Gerhard Hoffmann wrote... >> >> Am 21.12.2017 um 21:07 schrieb LM: >>> Has anyone seen a NPN bipolar transistor with emitter in >>> the middle, tab. Emitter is easier to ground in RF amplifiers. >> >> Yes. >> Infineon BFQ790. > > And Mini-Circuits wideband RF amplifiers, that come in 3-pin > SOT-89 packages, with an inductor to the supply bus, 50-ohm > IN and 50-ohm OUT, have their tab and middle pin grounded.Those can make an easy RF amplifier, true. Having the isolation between emitter and collector on the chip or having a large capacitance and area in the collector because of heatsinking. Or using some virus size chip no one will solder.
Reply by ●December 23, 20172017-12-23
