Twin T circuit wanted
in [Basics]
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From: Jim Thompson on 10 Jun 2010 21:10 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: [snip] >> >>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. > [snip jerkism] > >-YD. YD is normally blocked. Since JL responded... I will, in due course. I'm waiting, and hoping, that some young buck has a clear head, and can analyze it. ...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
From: John Larkin on 10 Jun 2010 21:11 On Thu, 10 Jun 2010 17:21:02 -0700 (PDT), MooseFET <kensmith(a)rahul.net> wrote: >On Jun 11, 12:01 am, John Larkin >[....] >> 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. > ><PITA> >Make that "electronic computers". At one time, a computer was >a person who computed. Companies had rooms full of people >grinding through the numbers to make sure that the sums were >right. ></PITA> <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> > >There were also some analog computers and mechanical >computers. Each generation has used the tools made by >the previous. Just try to imagine designing with Roman >numerals and not even a slide rule. > > >> 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 use spice as a sanity check. Sometimes it even finds some. > >LTSpice is also nice for making a schematic to email to someone. It is just about the only portable schematic format the industry has ever seen. Not a bad editor, but the circuits seem to wander all over the screen as you zoom. I have to keep selecting my whole circuit and dragging it back into sight. John
From: John Larkin on 10 Jun 2010 21:13 On Thu, 10 Jun 2010 17:37:34 -0700 (PDT), MooseFET <kensmith(a)rahul.net> wrote: >On Jun 10, 11:06 pm, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >[....] >> Can you think of other ways to make a very frequency and amplitude >> stable sine wave using early-70s technology? I suppose that a square >> wave generator and bandpass filter would work, but that's more parts. > >A tuning fork "self hummer" circuit using inductive drive and >inductive pick-up could be quite frequency stable. > >Amplitude stability comes from making the >cathode current on the 6SN7 nearly constant with >a really high voltage supply and a large resistor. > > What would determine the sinewave amplitude? John
From: Jim Thompson on 10 Jun 2010 21:16 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. Yep. "Ooopses" happen. As soon as I describe it on Sunday or Monday, you'll see how simple it is to understand. Off to SFO at dawn... NO I'm not seeing Larkin... I'm heading to Palo Alto ;-) ...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
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. |