Twin T circuit wanted
in [Design]
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From: YD on 10 Jun 2010 21:50 Late at night, by candle light, John Fields <jfields(a)austininstruments.com> penned this immortal opus: >On Thu, 10 Jun 2010 20:58:49 -0300, YD <ydtechHAT(a)techie.com> wrote: > >>Late at night, by candle light, Jim Thompson >><To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> penned this >>immortal opus: >> >>>On Thu, 10 Jun 2010 07:03:49 -0500, John Fields >>><jfields(a)austininstruments.com> wrote: >>> >>>>On Wed, 09 Jun 2010 20:46:42 -0700, John Larkin >>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>On 9 Jun 2010 19:18:40 -0700, Winfield Hill >>>>><Winfield_member(a)newsguy.com> wrote: >>>>> >>>>>>Jim Thompson wrote... >>>>>>> >>>>>>>>> I know John won't respond, but could someone, perhaps Win, tell me >>>>>>>>> how the "AGC" works? >>>>>>>> >>>>>>>> I'm sure he would, but why should I, over the years you've insulted >>>>>>>> me at least as much as him, and perhaps more aggressively? >>>>>>>> >>>>>>>> Anyway, he did explain it, SFAICT. >>>>>>>> >>>>>>>> Note the BJT is over-biased - plenty of base current, that if left >>>>>>>> unchecked would charge the base-to-ground capacitor and over-current >>>>>>>> the transistor. So the oscillator runs and examining cycle-by-cycle, >>>>>>>> the collector swings higher and higher until it goes negative with >>>>>>>> respect to the base voltage, close to saturating the transistor, >>>>>>>> and turning on the base-collector diode a bit, robbing current from >>>>>>>> the base capacitor. This process servos the BJT current to just the >>>>>>>> right level to sustain an oscillation collector-voltage level where >>>>>>>> just the right amount of current is robbed each cycle to control the >>>>>>>> base voltage. Thereby insuring that the collector goes close to the >>>>>>>> emitter on each cycle, establishing a tightly-controlled amplitude, >>>>>>>> which as John pointed out, is temperature independent to first order >>>>>>>> since Vce(sat) is relatively temperature independent. >>>>>>>> >>>>>>>> John said Vcc peak, but actually it must be closer to Vcc - Vce(sat). >>>>>>> >>>>>>> I'll buy that the collector forwards biases, and you enter a limit >>>>>>> cycle. Thus I'd call it ALC. I don't see any _gain_ variation that >>>>>>> "AGC" would imply. >>>>>> >>>>>> Picky, picky. To my mind, the base current robbed by the >>>>>> collector starves the base, lowering the CE stage's gain, >>>>>> until the exact equilibrium is achieved. ALC, AGC, pick >>>>>> your name as you like. Either way it gets the job done >>>>>> rather nicely, and is a bit different from what we've seen >>>>>> elsewhere, such as in old radio circuits. I see that it >>>>>> has been analyzed as a possible RF oscillator technique. >>>>>> But it seems to me that, working as we imagine, Vce(sat) >>>>>> and all, this trick would be limited to far far below fT. >>>>> >>>>>When I post circuits, JT and JF pull out dictionaries and start >>>>>arguing about what words mean. Circuits don't spend much time reading >>>>>dictionaries. >>>> >>>>--- >>>>Neither do you, obviously. ;) >>> >>>Larkin copies circuits from others, Rohde in this case, then totally >>>blows the explanation. >>> >>>Then, unfortunately, Win has backed up the BAD explanation :-( >>> >>> ...Jim Thompson >> >>So cough up the GOOD explation, or shut up. > >--- >Why not let Win defend himself instead of adding to the fray? >--- I'm speaking to Jim, not his side-kick. > >>Hey, why don't you three join up in a skiffle or jug band, "Two Johns >>And A Jim"? > >--- >Maybe because, so far, we like to play in different keys. Could be "The Three Jays" too. -YD. -- File corruption detected. Select option: 1 - Call the cops 2 - Call the press 3 - Bribe it Remove HAT if replying by mail.
From: Michael A. Terrell on 10 Jun 2010 22:37 John Larkin wrote: > > <OLDFARTSTORY> > > My first real job was a research assistant in microwave spectroscopy, > a summer tech job. Two grad students on the same project spent the > entire summer hunched over a Friden calculator in a small room, > calculating rotational resonances for some organic thing. My PC could > do all that now in, probably, a millisecond. > > </OLDFARTSTORY> Maybe, but your pc doesn't drink beer or chase cute college girls. ;-) -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
From: George Herold on 10 Jun 2010 22:39 On Jun 10, 2:59 pm, John Fields <jfie...(a)austininstruments.com> wrote: > On Thu, 10 Jun 2010 09:01:11 -0700, John Larkin > > > > > > <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >On Thu, 10 Jun 2010 09:09:55 -0500, John Fields > ><jfie...(a)austininstruments.com> wrote: > > >>On Thu, 10 Jun 2010 06:56:15 -0700, John Larkin > >><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>>On Thu, 10 Jun 2010 07:27:47 -0500, John Fields > >>><jfie...(a)austininstruments.com> wrote: > > >>>>On Wed, 09 Jun 2010 21:01:19 -0700, John Larkin > >>>><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>>>>On Wed, 09 Jun 2010 16:02:57 -0500, John Fields > >>>>><jfie...(a)austininstruments.com> wrote: > > >>>>>>On Wed, 09 Jun 2010 10:30:37 -0700, John Larkin > >>>>>><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>>>>>>On Wed, 09 Jun 2010 11:31:31 -0500, John Fields > >>>>>>><jfie...(a)austininstruments.com> wrote: > > >>>>>>>>On Tue, 08 Jun 2010 15:09:51 -0700, John Larkin > >>>>>>>><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > > >>>>>>>>>If I claimed that there was nitrogen in the air, he and > >>>>>>>>>JF would hack a Spice simulation and prove me wrong. > > >>>>>>>>--- > >>>>>>>>You're being absurd, as usual, but it seems you lucked out this time > >>>>>>>>and your oscillator works in LTspice. > > >>>>>>>Since we manufactured and sold lots of them before Spice was > >>>>>>>available, and they worked just fine, the luck is on Spice's part. Or > >>>>>>>yours. > > >>>>>>>This will shock the kiddies, but it *is* possible to design circuits > >>>>>>>without using Spice. Usually it's faster and better. > > >>>>>>--- > >>>>>>You're preaching to the choir, bucko. > > >>>>>>In your world, maybe, but when you're talking circuits with hundreds > >>>>>>of thousands or millions of transistors, it's not possible. > > >>>>>>This may come as a surprise to you, but many (if not most) of the > >>>>>>circuits which you buy and incorporate into your products were > >>>>>>designed using SPICE, so the fact that you assemble them into working > >>>>>>product that you don't simulate doesn't mean it's free of SPICE. > > >>>>>SPICE 1 was introduced at a conference in 1973. It wasn't very good, > >>>>>and SPICE 2, 1975, was better. DRAMS were introduced in 1970. > > >>>>--- > >>>>Red herring, cheater, or, at the very least, ignoratio elenchi. > > >>>The first few generations of RAM were designed before Spice existed, > >>>which you declared to be "not possible." > > >>>I don't know how to say that in Latin. > > >>--- > >>Pity, as is your lack of Englishy reading comprehension, since the > >>point which was being made was that even though you pooh-pooh SPICE, > >>your livelihood, today, depends on it. > > >I don't think so. People designed radar, magnetrons and klystrons and > >waveguides and servos and all that, without computers. They did the > >math. Early computers were obviously designed without help from > >computers. > > >I don't use Spice a lot, and could certainly get along without it. It > >is helpful when evaluating nonlinear systems, where math solutions get > >messy. > > --- > I don't know why you're being so argumentative when it's as clear as > the nose on your face that if SPICE didn't exist you'd have very > little on your plate to offer for sale. > > A couple of posts back I wrote: > > "This may come as a surprise to you, but many (if not most) of the > circuits which you buy and incorporate into your products were > designed using SPICE, so the fact that you assemble them into working > product that you don't simulate doesn't mean it's free of SPICE." > > SPICE is an acronym for "Simulation Program with Integrated Circuit > Emphasis", and I'm pretty sure you use chips designed using SPICE so > even if you don't simulate circuits at the board level, SPICE is still > in there. > > Also, SPICE is being used successfully in general circuit simulation > all around the world, so your naysaying is largely falling on ears > that know better. > > Personally, I've been doing circuit design for almost 50 years and I > used to avoid simulators like the plague. > > I've been using LTSpice for 3 or 4 years now and although I can get > along without it, there's no reason on earth I'd want to since typing > is a whole lot easier than wire-wrapping.- Hide quoted text - > > - Show quoted text - That's cool, so at a year and 1/2 I'm not that far behind. (Well I've only been doing circuit design for ten years...Still way behind) George H.
From: John Larkin on 10 Jun 2010 22:59 On 10 Jun 2010 17:55:23 -0700, Winfield Hill <Winfield_member(a)newsguy.com> wrote: >John Larkin wrote... >> >> I have never called myself a "judge", and Win has never called >> himself a "master." You and JT call us that, so you can then >> abuse us for saying things we never said. How lame. > > That's correct. I work hard at what I do, but I'm always > on the lookout for mistakes I may make, or more often, > things I don't yet understand. Hopefully I'll not pipe > up about something I don't yet understand, but oops, oops, > sometimes one doesn't yet know that they don't understand > something, or they may just make a silly thoughtless mistake. A lot depends on how fragile your ego is. If you are determined to always be "right" in public, or you are determined that someone else is always wrong, you'll be a fathead and not learn anything. Of course, there are some people who are AlwaysWrong. John
From: Jim Thompson on 10 Jun 2010 23:42
On Thu, 10 Jun 2010 19:59:50 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On 10 Jun 2010 17:55:23 -0700, Winfield Hill ><Winfield_member(a)newsguy.com> wrote: > >>John Larkin wrote... >>> >>> I have never called myself a "judge", and Win has never called >>> himself a "master." You and JT call us that, so you can then >>> abuse us for saying things we never said. How lame. >> >> That's correct. I work hard at what I do, but I'm always >> on the lookout for mistakes I may make, or more often, >> things I don't yet understand. Hopefully I'll not pipe >> up about something I don't yet understand, but oops, oops, >> sometimes one doesn't yet know that they don't understand >> something, or they may just make a silly thoughtless mistake. > >A lot depends on how fragile your ego is. If you are determined to >always be "right" in public, or you are determined that someone else >is always wrong, you'll be a fathead and not learn anything. > >Of course, there are some people who are AlwaysWrong. > >John Describing yourself, John ?:-) ...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 | The only thing bipartisan in this country is hypocrisy |