Maintaining a Vbe Multiplier's bias value
in [Design]
|
Prev: Cushman CE-24A
Next: TIA Photodiode Bootstrap at 10MHz
From: Jon Kirwan on 12 Feb 2010 02:15 On Thu, 11 Feb 2010 20:18:24 -0800, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Thu, 11 Feb 2010 19:04:07 -0800 (PST), George Herold ><ggherold(a)gmail.com> wrote: > >><snip> >> >>So how do you do push pull with tubes, or say with only Jon's npn >>transistors? >> >>George H. > >Usually two "NPN" tubes whose plates drive a center-tapped output >transformer. > >John Just to be clear, with B+ at the center-tap. Jon
From: Jon Kirwan on 12 Feb 2010 02:19 On Fri, 12 Feb 2010 05:33:02 +0100, "Ban" <bansuri(a)web.de> wrote: ><snip> > >A very comprehensive book, bible lets say is >The Crcuits and Filters Handbook by Chen >don't get fooled by "Handbook", it's the biggest book I got. :-)) >ciao Ban Cripes. If you walked into the house you'd see walls of polished bookshelves from floor to ceiling covering every spare bit of wall space in my library off the mail hall. I'm already overflowing out of there into another room and my wife isn't exactly happy about it. But what's another book or two? ;) I'll add it to my next order from somewhere. Jon
From: Jim Thompson on 12 Feb 2010 09:36 On Thu, 11 Feb 2010 19:37:27 -0800, Jon Kirwan <jonk(a)infinitefactors.org> wrote: >On Thu, 11 Feb 2010 19:23:04 -0800 (PST), George Herold ><ggherold(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 -- | 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: Jim Thompson on 12 Feb 2010 09:52 On Thu, 11 Feb 2010 23:13:24 -0500, Phil Hobbs <pcdhSpamMeSenseless(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 at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Jim Thompson on 12 Feb 2010 10:00
On Fri, 12 Feb 2010 05:38:21 +0100, "Ban" <bansuri(a)web.de> wrote: > >"George Herold" <ggherold(a)gmail.com> schrieb im Newsbeitrag >news:f7a4838e-716b-40a8-9b19-7c65cf86dff9(a)o3g2000yqb.googlegroups.com... >On Feb 11, 11:08 pm, "Phil Allison" <phi...(a)tpg.com.au> wrote: >> "George Herold >> >> So how do you do push pull with tubes, or say with only Jon's npn >> transistors? >> >> ** There are literally *millions* of push-pull tube amps in use - the vast >> majority of tube hifi and guitar amps are push pull designs. >> >> NPN output transistor amps are called "quasi-complementary push pull " - >> many millions of them made and sold too. >> >> Use Google to find the schems. >> >> Idiot. >> >> .... Phil > >>Thanks Phil I'll try google. Why are there still so many tube amps? >>You'd think someone could make a solid state amp that sounded >>'right'. > >A lot of transistor amps sound right, but some people prefer to add a bit of >2nd harmonics, or they want to enjoy the gloom. >ciao Ban > What? For playing your favorite atonal pieces by Schoenberg, Berg, Stravinsky, or Webern ?:-) Back in college, 4 semesters of classical music provided me with "easy A electives", but my wife would come unglued after just a few minutes of those guys ;-) ...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. |