Maintaining a Vbe Multiplier's bias value
in [Design]
|
Prev: Cushman CE-24A
Next: TIA Photodiode Bootstrap at 10MHz
From: John Larkin on 12 Feb 2010 11:24 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
From: George Herold on 12 Feb 2010 11:27 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, Im building electronics to either detect something or drive > >>> something thats 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.
From: Jim Thompson on 12 Feb 2010 11:54 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 !!! ...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: Jon Kirwan on 12 Feb 2010 14:02 On Fri, 12 Feb 2010 07:36:52 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >On Thu, 11 Feb 2010 19:37:27 -0800, Jon Kirwan ><jonk(a)infinitefactors.org> wrote: > >>><snip> >> >>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 Almost. It's more like: I'd like to get to Fresno Flats (aka Oakhurst, near Yosemite) from Portland, but rather than just fly there (okay, so I have to parachute out) I'd like to enjoy the trip this time, too, and detour around a bit to some of the sights along the way. First off, maybe to the Opal Creek Wilderness area to see some of the 800 year old cedar groves; then maybe south to a short visit at White's Electronics in Sweet Home; then to Crater Lake; maybe then to Oregon Caves; off perhaps to do some panning for gold in Jackson County while also taking a hike in the Siskiyous; then on over to hwy 101 at Brookings to do some whale watching; down to Crescent City to visit the Jedediah Smith and Del Norte parks and see what's left of the redwoods there; .... Well, might as well make a thing of it this time 'round. Oakhurst won't go away while I'm on the road. Jon
From: John Larkin on 12 Feb 2010 15:18
On Fri, 12 Feb 2010 08:16:34 -0800 (PST), George Herold <ggherold(a)gmail.com> wrote: >On Feb 12, 9:52�am, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- >Web-Site.com> wrote: >> On Thu, 11 Feb 2010 23:13:24 -0500, Phil Hobbs >> >> >> >> >> >> <pcdhSpamMeSensel...(a)electrooptical.net> wrote: >> >On 2/11/2010 10:35 PM, George Herold wrote: >> >> On Feb 11, 1:14 pm, John Larkin >> >> <jjlar...(a)highNOTlandTHIStechnologyPART.com> �wrote: >> >>> On Thu, 11 Feb 2010 10:08:38 -0600, "Tim Williams" >> >> >>> <tmoran...(a)charter.net> �wrote: >> >>>> "Jim Thompson"<To-Email-Use-The-Envelope-I...(a)My-Web-Site.com> �wrote in >> >>>> messagenews:r358n59g5vkv4brn2vc795lhoineb2jvhd(a)4ax.com... >> >>>>> And a 2.5V "dead-band", but it _is_ precisely known, and temperature >> >>>>> stable. �Interesting thought if you have high enough power supplies. >> >> >>>> Bonus: the dead band allows you to use that TL431 "Vbe" mentinoed earlier. >> >> >>>> Too bad they're so slow (hardly capable for audio). �Does anyone make "fast" >> >>>> regulators (without being stupid LDOs)? >> >> >>>> Tim >> >> >>> If you drive both adjust pins with the signal input, the 317 output is >> >>> Vin+1.25 and the 337 output is Vin-1.25. Connect them to the output >> >>> through a couple of resistors, valued to set the idle current. Where's >> >>> the deadband? >> >> >>> Or you can take the output from the 317 output pin, with the 337 now >> >>> acting like a constant-current sink to the 317. >> >> >>> I like to use LM1117s as power emitter followers, inside the loop of >> >>> an opamp. That makes a cheap, well protected power driver, for load >> >>> cell excitation and such. I did a bunch of tests to see whether >> >>> flailing the adj pin can damage the regulator, and never managed to >> >>> break one. >> >> >>> John >> >> >> Cool! �I think I got it... though if I try it in the future and let >> >> the smoke out of something... then I might have questions. >> >> >> George H. >> >> >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 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. >> >> � � � � � � � � � � � � � � � � � � � � ...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 athttp://www.analog-innovations.com| � �1962 � � | >> >> I love to cook with wine. � � Sometimes I even put it in the food.- Hide quoted text - >> >> - Show quoted text - > >Thanks Jim, I always wondered why there wasn't a compliment to the >LM395. (And why the negative voltage regulators would 'wig out' if >you didn't follow the cap reccomendations.) > >George H. There are lots of positive LDOs around these days that have PNP (namely high impedance) outputs. They tend to be very picky about output capacitance ESR and such, with appropriately evasive datasheets. I had one powering an FPGA core, putting a 0.2 volt p-p, 50 KHz triangle into the poor chip. That caused a lot of jitter. John |