Twin T circuit wanted
in [Design]
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From: Vladimir Vassilevsky on 9 Jun 2010 13:35 John Larkin wrote: > This will shock the kiddies, but it *is* possible to design circuits > without using Spice. Usually it's faster and better. That's what I tell them. Archimedes, Newton and Einstein perfectly managed without Matlabs, Simulinks and Spices. VLV
From: John Fields on 9 Jun 2010 17:02 On Wed, 09 Jun 2010 10:30:37 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Wed, 09 Jun 2010 11:31:31 -0500, John Fields ><jfields(a)austininstruments.com> wrote: > >>On Tue, 08 Jun 2010 15:09:51 -0700, John Larkin >><jjlarkin(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.
From: Jim Thompson on 9 Jun 2010 19:43 On Mon, 07 Jun 2010 20:33:23 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: [snip] > >The cool thing is that the collector swing is almost exactly 2xVcc >peak-to-peak. As the amplitude builds up, at the negative swing peak >the emitter goes a little bit negative, to get out of the way, and the >collector swings to just about ground. That forward-biases the c-b >junction and discharges the base cap, reducing transistor base current >hence gain. So it has a built-in peak detecting AGC amplitude >levelling loop with close to zero TC. All from 5 parts. Or sometimes >six. > [snip] I know John won't respond, but could someone, perhaps Win, tell me how the "AGC" works? ...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: Phil Hobbs on 9 Jun 2010 20:40 John Larkin wrote: > On Wed, 09 Jun 2010 11:31:31 -0500, John Fields > <jfields(a)austininstruments.com> wrote: > >> On Tue, 08 Jun 2010 15:09:51 -0700, John Larkin >> <jjlarkin(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. > > John I'm not a big SPICE user in general, though I've done more SPICEing in the last year than in the 20 previous. For some things, such as really weird photodiode preamps where nonlinear capacitances and so on are important, it can help a lot--provided the models are semi-decent. For most other things, I prefer algebra. You learn a lot more about how the circuit works by crunching the math than by poking the simulation until it seems to work. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: John Larkin on 9 Jun 2010 21:19
On Wed, 09 Jun 2010 20:40:37 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >John Larkin wrote: >> On Wed, 09 Jun 2010 11:31:31 -0500, John Fields >> <jfields(a)austininstruments.com> wrote: >> >>> On Tue, 08 Jun 2010 15:09:51 -0700, John Larkin >>> <jjlarkin(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. >> >> John > >I'm not a big SPICE user in general, though I've done more SPICEing in >the last year than in the 20 previous. > >For some things, such as really weird photodiode preamps where nonlinear >capacitances and so on are important, it can help a lot--provided the >models are semi-decent. For most other things, I prefer algebra. You >learn a lot more about how the circuit works by crunching the math than >by poking the simulation until it seems to work. > >Cheers > >Phil Hobbs Spice is handy for tweaking control loops, especially higher-order loops that matter, or when anything nonlinear is going on. Or when you don't have a hard definition of what "right" is. Simple opamp type things are better to do with guesswork, or a scribbled Bode plot. You lose points if you use a calculator. Spice is good for filters, too. I did a constant-voltage/constant-current crossover power supply sort of thing recently, analog ORing two loop error signals, with a wide range of possible customer loads, and it was great for tweaking. The actual implementation will be firmware. The other good use for Spice is grinding out the numbers on voltage dividers, pure DC analysis, just to save a lot of calculator stuff. We never simulate whole products, or even whole circuits, just little pieces, or control loop abstractions. John |