Maintaining a Vbe Multiplier's bias value
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From: Jim Thompson on 12 Feb 2010 16:38 On Fri, 12 Feb 2010 14:25:06 -0700, "bg" <bg(a)nospam.com> wrote: > >Jim Thompson wrote in message ... >>On Fri, 12 Feb 2010 13:43:37 -0700, "bg" <bg(a)nospam.com> wrote: >> >>>big snip - >>> >> >>Son of a gun. Yesterday you couldn't even spell "engineer", now you >>are one (;-0 > >I finally did something right? Wow!!! > Actually you found the "art" part needed to rough-in a design. Now go back and fix the flaws ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Phil Hobbs on 12 Feb 2010 16:42 On 2/12/2010 11:24 AM, John Larkin wrote: > On Fri, 12 Feb 2010 10:03:11 -0500, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > > >> >> Build a man a fire, you keep him warm for a night. Set a man afire, you >> keep him warm for the rest of his life. ;) >> >> Cheers >> >> Phil Hobbs > > > Got snow? > > John > About a foot, day before yesterday. 45 and sunny yesterday and today. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs at electrooptical dot net http://electrooptical.net
From: Phil Hobbs on 12 Feb 2010 16:43 On 2/12/2010 11:27 AM, George Herold wrote: > On Feb 12, 10:03 am, Phil Hobbs > <pcdhSpamMeSensel...(a)electrooptical.net> wrote: >> On 2/12/2010 9:36 AM, Jim Thompson wrote: >> >> >> >> >> >>> On Thu, 11 Feb 2010 19:37:27 -0800, Jon Kirwan >>> <j...(a)infinitefactors.org> wrote: >> >>>> On Thu, 11 Feb 2010 19:23:04 -0800 (PST), George Herold >>>> <ggher...(a)gmail.com> wrote: >> >>>>> On Feb 11, 3:24 am, Jon Kirwan<j...(a)infinitefactors.org> wrote: >>>>>> On Wed, 10 Feb 2010 19:55:44 -0800 (PST), George Herold >> >>>>>> <ggher...(a)gmail.com> wrote: >>>>>>> I'm perhaps more of a novice than you... >> >>>>>> Somehow, I doubt that. I barely rate "hobbyist." >> >>>>>>> but I find opamp circuits complicated enough.... >> >>>>>> Don't sweat it. While some opamps leave _some_ issues nearly >>>>>> ignorable, there is always some tough problem at that scale >>>>>> that makes it non-trivial and interesting to work on, I >>>>>> imagine. Each macroscale view has it's own complexity. >>>>>> Telescoping levels, where the complexity at one stage doesn't >>>>>> take away from interesting complexity at another level. >> >>>>>> (I would say more but I'm keeping in mind your warning about >>>>>> long-windedness and will now muzzle myself.) >> >>>>>>> And tend to stick transistors >>>>>>> only on the edges of things. (Mostly on the output side... on the >>>>>>> input you have to 'know more' than the guys who designed the opamp... >>>>>>> hard to do for a novice.) >> >>>>>> I do the same things except that I enjoy math and BJTs give >>>>>> me an excuse, perhaps. Maybe that's the only difference. >> >>>>>>> I guess if I was designing an audio amp I'd figure on an opamp driving >>>>>>> some sort of FET output stage. The question of how to bias the output >>>>>>> stage is interesting. And also of how all the NFB works. >> >>>>>> Might as well just get a power opamp like the OPA502 and be >>>>>> done with it. Give it two rails, feed the input, and just >>>>>> drive the hell out of a speaker. Or get two of them and do a >>>>>> bridge amplifier. But where is the enjoyment in that? Or >>>>>> the learning? Someone else already did most of the fun stuff >>>>>> and there's nothing really left to do except some hook up and >>>>>> heat sinking. It's not at all satisfying to me, anyway. >> >>>>>> An audio amplifier is basically a power opamp. Using an >>>>>> opamp to make one feels to me like building a car by first >>>>>> buying a car without the tires, selecting and installing some >>>>>> tires, and then saying you designed and built yourself a car. >> >>>>>> Jon >> >>>>> Big Grins! >> >>>>> Yeah I applaud your effort, I wait for further posts. >> >>>>> For me, I�m building electronics to either detect something or drive >>>>> something that�s detecting something. So the fun is in making good >>>>> detectors or drivers. >> >>>>> George H. >> >>>> Well, I am wanting, eventually, to build something I need. >>>> Something I cannot buy in the market because the need is >>>> unique. >> >>>> This divides into two parts. Design and build. Since the >>>> item is unique, I can't just go out and buy it. And getting >>>> the features I need cannot just be "hacked" into existing >>>> designs without at least knowing _some_ stuff, first. I >>>> might as well turn the "design" part into a fair learning >>>> experience, as a separate project of its own. Get past that >>>> and when it comes time to build what I want I'll be able to >>>> build on what I learned and add what I need and then do a >>>> modest hobbyist level whack at actually making what I want to >>>> make. >> >>>> If someone else were to do this for me (hire a designer), >>>> they'd get all the fun of learning on the job and taking my >>>> money with it. They get the money, they get to further their >>>> own education, and I get a tool. One tool. Once. Next >>>> time, I get to pay someone else to learn for me. >> >>>> It almost feels like paying someone to go do your exercising >>>> for you. No satisfaction and no weight loss. They get all >>>> the _real_ benefits. >> >>>> Part of the fun isn't the destination itself but it is what >>>> you see and enjoy while getting there, too. You take a plane >>>> when all you need is to "get there" quick, but you drive when >>>> you want to enjoy stops along the way. I used to fly to >>>> Burbank every week for a year and a half. Slept in a hotel >>>> for 3 nights a week, worked day and night in between, flew >>>> home. Barely saw anything but hotel room walls, cubical >>>> walls, a few cement roads, pollution so thick you couldn't >>>> see the Burbank hills from the Lockheed center, and not much >>>> else. The destination was important, of course. Paid the >>>> bills and I enjoyed the work, too. But there is a lot more >>>> to see in the 1000 miles from here to there. >> >>>> Anyway, I'm driving this time, not flying. >> >>>> Besides, I'd rather _keep_ the money and _keep_ the education >>>> for myself. That way it pays off, again and again. >> >>>> Jon >> >>> The fish/fish rule ?:-) >> >>> ...Jim Thompson >> >> Build a man a fire, you keep him warm for a night. Set a man afire, you >> keep him warm for the rest of his life. ;) >> >> Cheers >> >> Phil Hobbs >> >> -- >> Dr Philip C D Hobbs >> Principal >> ElectroOptical Innovations >> 55 Orchard Rd >> Briarcliff Manor NY 10510 >> 845-480-2058 >> >> email: hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text - >> >> - Show quoted text - > > "> Build a man a fire, you keep him warm for a night. Set a man > afire, you >> keep him warm for the rest of his life. ;)" > > Can't help being reminded of "The Cremation of Sam McGee". > > And there sat Sam, looking cool and calm, in the heart of the furnace > roar; > And he wore a smile you could see a mile, and he said: "Please close > that door. > It's fine in here, but I greatly fear you'll let in the cold and storm > � > Since I left Plumtree, down in Tennessee, it's the first time I've > been warm." > > Taken from here, > "http://en.wikisource.org/wiki/The_Cremation_of_Sam_McGee" > > George h. Yep, that was quite a night on the marge of Lake LaBarge. Cheers Phil 'sourdough' Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs at electrooptical dot net http://electrooptical.net
From: krw on 12 Feb 2010 16:54 On Fri, 12 Feb 2010 13:21:58 -0800, "Bob Monsen" <rcmonsen(a)gmail.com> wrote: > > >"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in >message news:0m1bn5ln6ag64hdqnmr4te1qjeiec22i02(a)4ax.com... >> On Fri, 12 Feb 2010 08:23:36 -0800, John Larkin >> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Fri, 12 Feb 2010 10:23:24 -0500, Phil Hobbs >>><pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>> >>>>On 2/12/2010 9:52 AM, Jim Thompson wrote: >>>>> On Thu, 11 Feb 2010 23:13:24 -0500, Phil Hobbs >>>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> [snip] >>>>>> >>>>>> IIRC the LM395 is basically an LM309 with the voltage reference >>>>>> removed. >>>>>> Emitter-follower regulators are nearly bulletproof unless you >>>>>> discharge a cap into the output. >>>>>> >>>>>> Cheers >>>>>> >>>>>> Phil Hobbs >>>>> >>>>> Close, but no cigar, LM395 = LM317 with some metal rearrangements. >>>>> >>>>I was thinking 317 but then I decided that the 395 was older than that. >>>> I guess not. >>>> >>>>> I did this analysis for ICE back in 1980: >>>>> >>>>> http://analog-innovations.com/SED/ICE-LM195-LM117.pdf >>>>> >>>>> Additionally: Amusing myself with the thoughts of complementary- >>>>> follower-style power amplifiers made from LM317/LM337 pairs, it fails >>>>> because both, internally, are NPN's pass devices, so the LM337 has GBW >>>>> and stability issues plus it needs substantial idle load to stay >>>>> _vaguely_ stable. >>>> >>>>Non-LDO three-terminal regulators are so trouble-free that it's easy to >>>>confuse them with Newton's laws. ;) >>>> >>>>Cheers >>>> >>>>Phil Hobbs >>> >>>LM1117 is an "MDO" regulator. It has an NPN pass transistor but a bit >>>lower dropout voltage than an LM317. Its ideal as a 3.3-to-1.25 volt >>>FPGA core voltage source... no resistors! My purchasing notes say "Do >>>not buy Fairchild per JL" but I can't recall why. >>> >>>As with all vregs, one has to be careful about the output capacitors. >>> >>>John >> >> I'm puzzled why the big semiconductor houses don't turn out discrete >> LDO's on a CMOS process. I do it all the time on complex CMOS >> ASIC's... like a PLL chip, fundamental power fed from +3.3V, but >> internal regulators producing +2.5V and +1.8V... at hundreds of mA !!! >> > >ST Arm Cortex-M3 has an internal 1.8V regulator for the core, and can take >any input voltage from 2.0 to 3.8V. Same with the Altera Max-II CPLDs. They'll take 1.8V, 2.5V, or 3.3V.
From: krw on 12 Feb 2010 17:07
On Fri, 12 Feb 2010 08:24:24 -0800, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Fri, 12 Feb 2010 10:03:11 -0500, Phil Hobbs ><pcdhSpamMeSenseless(a)electrooptical.net> wrote: > > >> >>Build a man a fire, you keep him warm for a night. Set a man afire, you >>keep him warm for the rest of his life. ;) >> >>Cheers >> >>Phil Hobbs > > >Got snow? We have about 1" now. They cancelled work for today about 9:30 last night. Since there was no snow this morning (it started about 10:00AM) I went into work. I was the only one there. My wife's employer closed about 2:00, with less than 1" on the ground. The streets are just now starting to get some slush on them. I guess it's a good thing the locals are scared shitless of snow. |