Twin T circuit wanted
in [Basics]
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From: John Larkin on 10 Jun 2010 15:20 On Thu, 10 Jun 2010 14:06:25 -0500, John Fields <jfields(a)austininstruments.com> wrote: >On Thu, 10 Jun 2010 09:36:33 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Thu, 10 Jun 2010 11:02:49 -0500, John Fields >><jfields(a)austininstruments.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. >>>> >>>>Got any ideas? >>> >>>--- >>>Tuning fork oscillator. >> >>Why would that be amplitude stable? > >--- >Please... Answer the question. John
From: BlindBaby on 10 Jun 2010 15:21 On Thu, 10 Jun 2010 12:13:32 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >Neither simulation nor breadboarding is a safe substitute for >understanding what's going on. > That's what those of us that understand the importance of simulation are trying to tell YOU. Nice snip of the calculator and clipboard reference, supporting your pathetic claim that I do not know what is going on and do not do math. Sorry, Johnny, but that math on that bright move is pretty evident, loser. Since you are so against it, it is obvious that it is YOU that "does not know what is going on".
From: BlindBaby on 10 Jun 2010 15:45 On Thu, 10 Jun 2010 12:17:19 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Thu, 10 Jun 2010 11:54:51 -0700, BlindBaby ><BlindMelonChitlin(a)wellnevergetthatonethealbumcover.org> wrote: > >>On Thu, 10 Jun 2010 11:37:12 -0700, John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Thu, 10 Jun 2010 09:46:13 -0700, BlindBaby >>><BlindMelonChitlin(a)wellnevergetthatonethealbumcover.org> wrote: >>> >>>>On Wed, 09 Jun 2010 10:30:37 -0700, John Larkin >>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>This will shock the kiddies, but it *is* possible to design circuits >>>>>without using Spice. Usually it's faster and better. >>>> >>>> >>>> It is usually faster, but these days, not usually better. And the >>>>speed gain is only about the operator of the sim package, not the sim. >>>>A good sim app user can beat you, hands down, and have reliable numbers >>>>to compare with real builds as well. >>>> >>>> Sim apps have gotten orders of magnitude tighter in their iterative >>>>analysis and inclusion of parasitics, etc. >>>> >>>> Far better than you, with or without your bench. >>> >>>Simulation is like breadboarding. Neither is designing. >>> >>>John >> >> >> You're an idiot. Sitting next to my breadboard is my clipboard and >>calculator, Johnny. >> > >Tell us about, or better show us, something you're designing. > >John Of what I can tell you about... a motor controller for an electric bike. Up to a 15kW peak burst capacity.
From: dagmargoodboat on 10 Jun 2010 15:50 John Larkin wrote: > dagmargoodb...(a)yahoo.com wrote: > > >On Jun 9, 9:18 pm, Winfield Hill wrote: > >> 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. > > >Just to clarify, the RF versions I posted are similar to, but not the > >same as John's. They're standard UHF designs, Class A, without John's > >precision AGC. I don't think they can use John's AGC method directly-- > >if saturated, the transistors would be too slow--but maybe a Baker-ish > >clamp thing would do the job. > > In my oscillator, a c-b schottky diode would keep the transistor c-b > junction from conducting, and keep the transistor out of saturation. > Tempco would still be low. That simplifies things considerably. Not > bad. Good idea. > >Oh, and John's oscillator really swings ~ 2* (Vcc + Vbe), not 2* (Vcc > >- Vbe). Reason being, the AGC operates as the average base voltage > >gets sucked down to near 0v, killing the gain. > > I seem to recall the DC base voltage being about +.6. So the collector > swings to just about zero, and the AC output is 2*Vcc p-p. Somebody > could Spice this, if they were interested, and see exactly what > happens. I Spice'd all the circuits I posted. > The transformer ratio gets involved some, too. Yep, but to a 1rst order: average emitter voltage = 0, ignore the swing 'cause it's small, and that gets you pretty close. V(b) = 120mV in my 5KHz example. James
From: Winfield Hill on 10 Jun 2010 16:30
Jim Thompson wrote... > > What was with, "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"? Where in the world did that come > from... Larkin's _incorrect_ description? Yep, CE was my mistake. Jim, I'm going to continue the conversation over in the part of the thread where the "John Larkin's LC oscillator" heading is, instead of "Twin T circuit wanted" - we don't want to get flamed again for being off topic. Meanwhile, you might think about the way the circuit works at low supply voltages near the end of a bell ring, just before it stops oscillating. -- Thanks, - Win |