On Tue, 16 Aug 2016 07:17:29 -0700 (PDT), dagmargoodboat@yahoo.com wrote:>On Tuesday, August 16, 2016 at 7:28:21 AM UTC-4, Steve Goldstein wrote: >> I'm looking for one or two of these arrays for a small home project. >> Yes, I know they're available from China on eBay, but I'd much rather >> find a couple of vintage (and authentic and working) parts from >> someone's bin. >> >> There may be other parts that are suitable, but this is the only array >> I remember where all the devices are fully pinned-out. This >> requirement is important and excludes LM3046 and similar parts. Device >> matching needn't be perfect as I can trim it out. The array needs to >> be junction isolated to ensure that all devices will be at as nearly >> the same temperature as possible - the old Harris HFA3127 is right out >> due to its use of dielectric isolation. >> >> Yes, I know it's a high-frequency array and I need to watch out for >> parasitic oscillations. I've used these before in my day job, but >> none remain in the parts drawers :( >> >> I'm building a temperature compensating gizmo that needs a current >> cuber, something I can in theory do as a translinear circuit with 5 >> transistors, a cheap quad op-amp, and some passives. The process I'm >> dealing with is exponential but the cubic function is gives a >> surprisingly good approximation to what I need over my limited >> temperature range. I'd like to start out with a translinear cuber >> because translinear is cool, but if that proves troublesome I can use >> the same array to make a copy of the AD538 - this would allow me to >> get a non-integer power that would be even more accurate. The real >> AD538 is still available but seems excessive at over $50 each in small >> quanitities. >> >> Hmm, I wonder if I can build a 538 clone with a less exotic array like >> a 3046... >> >> Thanks for any pointers. >> >> Hint - Remove the HAM to reply by email. > >I've got a tube of these (5 x NPN, RCA)-- >http://www.brown.edu/Departments/Engineering/Courses/En162/DataSheets/ca3083.pdf > >Good enough? > >Cheers, >James ArthurHi James, I'd completely forgotten about the CA3083 as I no longer have my antique NatSemi databooks (I gifted them to a friend). This would actually be preferable to the CA3127 as it's a lower-fT device and less prone to oscillation. The 5-transistor array gives me the option of a nifty translinear cuber or a "discrete" AD538. I was playing with the numbers today and found that I^2.7 gives an even better fit than I^3 over my temperature range, so the AD538 approach may win after all. I don't really _need_ that level of accuracy but after decades of working with precision electronics... Steve
Domestic US source for small quantity of CA3127 transistor array?
Started by ●August 16, 2016
Reply by ●August 16, 20162016-08-16
Reply by ●August 16, 20162016-08-16
>Nearly all my design activities for the past 10+ years have been with >dielectrically isolated processes. The earlier processes had device >thermal resistances of several thousand degrees per K, the newest one >is even higher. I'd rather not have to even worry about it.Don't know what you mean by that--degrees per kelvin??? Cheers Phil Hobbs
Reply by ●August 17, 20162016-08-17
On Tuesday, August 16, 2016 at 9:15:18 PM UTC-4, Steve Goldstein wrote:> On Tue, 16 Aug 2016 07:17:29 -0700 (PDT), dagmargoodboat@yahoo.com > wrote: > > >On Tuesday, August 16, 2016 at 7:28:21 AM UTC-4, Steve Goldstein wrote: > >> I'm looking for one or two of these arrays for a small home project. > >> Yes, I know they're available from China on eBay, but I'd much rather > >> find a couple of vintage (and authentic and working) parts from > >> someone's bin. > >> > >> There may be other parts that are suitable, but this is the only array > >> I remember where all the devices are fully pinned-out. This > >> requirement is important and excludes LM3046 and similar parts. Device > >> matching needn't be perfect as I can trim it out. The array needs to > >> be junction isolated to ensure that all devices will be at as nearly > >> the same temperature as possible - the old Harris HFA3127 is right out > >> due to its use of dielectric isolation. > >> > >> Yes, I know it's a high-frequency array and I need to watch out for > >> parasitic oscillations. I've used these before in my day job, but > >> none remain in the parts drawers :( > >> > >> I'm building a temperature compensating gizmo that needs a current > >> cuber, something I can in theory do as a translinear circuit with 5 > >> transistors, a cheap quad op-amp, and some passives. The process I'm > >> dealing with is exponential but the cubic function is gives a > >> surprisingly good approximation to what I need over my limited > >> temperature range. I'd like to start out with a translinear cuber > >> because translinear is cool, but if that proves troublesome I can use > >> the same array to make a copy of the AD538 - this would allow me to > >> get a non-integer power that would be even more accurate. The real > >> AD538 is still available but seems excessive at over $50 each in small > >> quanitities. > >> > >> Hmm, I wonder if I can build a 538 clone with a less exotic array like > >> a 3046... > >> > >> Thanks for any pointers. > >> > >> Hint - Remove the HAM to reply by email. > > > >I've got a tube of these (5 x NPN, RCA)-- > >http://www.brown.edu/Departments/Engineering/Courses/En162/DataSheets/ca3083.pdf > > > >Good enough? > > > >Cheers, > >James Arthur > > Hi James, > > I'd completely forgotten about the CA3083 as I no longer have my > antique NatSemi databooks (I gifted them to a friend). This would > actually be preferable to the CA3127 as it's a lower-fT device and > less prone to oscillation. The 5-transistor array gives me the option > of a nifty translinear cuber or a "discrete" AD538.I'd be happy to send some your way ... my e-mail is valid.> I was playing with the numbers today and found that I^2.7 gives an > even better fit than I^3 over my temperature range, so the AD538 > approach may win after all. I don't really _need_ that level of > accuracy but after decades of working with precision electronics... > > SteveCheers, James Arthur
Reply by ●August 17, 20162016-08-17
On Tue, 16 Aug 2016 18:19:49 -0700 (PDT), Phil Hobbs <pcdhobbs@gmail.com> wrote:>>Nearly all my design activities for the past 10+ years have been with >>dielectrically isolated processes. �The earlier processes had device >>thermal resistances of several thousand degrees per K, the newest one >>is even higher. �I'd rather not have to even worry about it. > >Don't know what you mean by that--degrees per kelvin??? > >Cheers > >Phil HobbsOops, degrees K per watt. I was stupider than usual last night. Advanced transistor models (Mextram is one) support individual transistor self-heating, which is extremely important in dielectrically isolated circuits. There's a global temperature variable to set the environment, but now each transistor's internal temperature can rise relative to the environment as a function of its instantaneous power dissipation, and this is taken account in setting all the temperature-dependent parameters for each device. This part of the model is fairly simple, a current source working into a parallel RC connected to thermal "ground", i.e. the environment, but the Mextram and other advanced models on the whole are way more complex than the basic Gummel-Poon model supported by most commonly-available simulators like PSPICE and LTSPICE, having about twice the number of parameters. Taking this heating into account is important in precision circuits, even with junction-isolated processes, but you'll be doomed if you don't include it when working with DI where the self-heating can be more than an order of magnitude worse than in JI. One challenge that's still out there is modeling the heat transfer between devices. This is actually a Very Hard Problem because it needs to be layout-aware. While there are a few researchers active in the area and occasionally publishing I'm not aware of any of this work making its way out of academia. Steve
Reply by ●August 17, 20162016-08-17
Several thousand K/W? For really small transistors, I'd believe that, but these array devices are pretty big. Anyway, chuck in an op amp or two and use the three-transistor cuber I posted upthread, with a MAT14. It has dramatically better matching and higher beta than those old RCA things. Plus you can have your 2.7th power just by changing a resistor, and you'll have a spare transistor to use as a heater to ovenize the die and get rid of drift. Cheers Phil Hobbs
Reply by ●August 17, 20162016-08-17
On Wed, 17 Aug 2016 04:16:45 -0700 (PDT), Phil Hobbs <pcdhobbs@gmail.com> wrote:>Several thousand K/W? For really small transistors, I'd believe that, but these array devices are pretty big. > >Anyway, chuck in an op amp or two and use the three-transistor cuber I posted upthread, with a MAT14. It has dramatically better matching and higher beta than those old RCA things. Plus you can have your 2.7th power just by changing a resistor, and you'll have a spare transistor to use as a heater to ovenize the die and get rid of drift. > >Cheers > >Phil HobbsYes, dielectrically isolated transistors in a modern process can run several thousand K/W. It's at least an order of magnitude greater than for comparably-sized JI devices. The devices in the CA3083 are much larger and should run even cooler so I may not have to worry about it. I was thinking to use the spare transistor as a heater - that'll need additional control circuity, which can be added later, if I want to temperature-stabilize the thing. I'd completely forgotten about the MAT-14. We might have some in the lab, it'll be interesting to compare them against the CA3083s that James is graciously sending me. Steve
Reply by ●August 18, 20162016-08-18
>Yes, dielectrically isolated transistors in a modern process can run >several thousand K/W. It's at least an order of magnitude greater >than for comparably-sized JI devices.I'm still seriously skeptical that those sorts of numbers can apply to these large array transistors--their theta_JA is a good 50 times less than that. That 200 nm of oxide must be doing serious magic. I wish my house insulation were that good! A reference would be a good place to start. Cheers Phil Hobbs
Reply by ●August 18, 20162016-08-18
On Wed, 17 Aug 2016 21:11:14 -0700 (PDT), Phil Hobbs <pcdhobbs@gmail.com> wrote:>>Yes, dielectrically isolated transistors in a modern process can run >>several thousand K/W. �It's at least an order of magnitude greater >>than for comparably-sized JI devices. > >I'm still seriously skeptical that those sorts of numbers can apply to these large array transistors--their theta_JA is a good 50 times less than that. That 200 nm of oxide must be doing serious magic. I wish my house insulation were that good! > >A reference would be a good place to start. > >Cheers > >Phil HobbsSorry, Phil, I can't provide any references off the top of my head, though I know there've been papers in IEEE journals. There was one about modeling heat transfer between devices (the Very Hard Problem I mentioned) in the past few years, I'll see if I can dig it up. Thousands of degrees per Watt is real, our model development guys routinely measure it as part of their work to develop models for new processes. You pretty much can't do any serious design in DI without taking temperature rise into account. Keep in mind these are small devices, say 0.35um x 5um emitters, 1-4 stripes and smaller. You're right that the relatively giant JI transistors in those old arrays probably have just a few percent of this thermal resistance. Steve
Reply by ●August 18, 20162016-08-18
On Thu, 18 Aug 2016 07:38:31 -0400, Steve Goldstein <sgoldHAM@alum.mit.edu> wrote:>On Wed, 17 Aug 2016 21:11:14 -0700 (PDT), Phil Hobbs ><pcdhobbs@gmail.com> wrote: > >>>Yes, dielectrically isolated transistors in a modern process can run >>>several thousand K/W. �It's at least an order of magnitude greater >>>than for comparably-sized JI devices. >> >>I'm still seriously skeptical that those sorts of numbers can apply to these large array transistors--their theta_JA is a good 50 times less than that. That 200 nm of oxide must be doing serious magic. I wish my house insulation were that good! >> >>A reference would be a good place to start. >> >>Cheers >> >>Phil Hobbs > >Sorry, Phil, I can't provide any references off the top of my head, >though I know there've been papers in IEEE journals. There was one >about modeling heat transfer between devices (the Very Hard Problem I >mentioned) in the past few years, I'll see if I can dig it up. > >Thousands of degrees per Watt is real, our model development guys >routinely measure it as part of their work to develop models for new >processes. You pretty much can't do any serious design in DI without >taking temperature rise into account. Keep in mind these are small >devices, say 0.35um x 5um emitters, 1-4 stripes and smaller. You're >right that the relatively giant JI transistors in those old arrays >probably have just a few percent of this thermal resistance. > >SteveHere's something I was able to find easily. I don't think it specifically mentions the high K/W for dielectrically isolated devices but it does address some of the subtleties in modeling multistripe and adjacent independent devices. I'll look around for more. Walkey, Smy, Dickson, Zweidinger, and Fox: Equivalent Circuit Modeling of Static Subtrate Thermal Coupling Using VCVS Representation, JSSC Vol 37 No 9, pp. 1198-1206. The sorts of K/W numbers I quoted are specific to the proprietary processes I work with but I imagine pretty much any modern dielectrically isolated complementary bipolar process will be in the same ballpark. Steve
