From: BlindBaby on
On Thu, 10 Jun 2010 09:37:04 -0700, John Larkin
<jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 10 Jun 2010 09:08:33 -0700, BlindBaby
><BlindMelonChitlin(a)wellnevergetthatonethealbumcover.org> wrote:
>
>>On Thu, 10 Jun 2010 11:02:49 -0500, John Fields
>><jfields(a)austininstruments.com> wrote:
>>
>>>On Thu, 10 Jun 2010 08:06:23 -0700, John Larkin
>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>On Thu, 10 Jun 2010 07:13:42 -0500, John Fields
>>>><jfields(a)austininstruments.com> wrote:
>>>>
>>>>>On Wed, 09 Jun 2010 20:42:20 -0700, John Larkin
>>>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>>>>
>>>>>>On 9 Jun 2010 18:54:01 -0700, Winfield Hill
>>>>>><Winfield_member(a)newsguy.com> wrote:
>>>>>>
>>>>>>>Jim Thompson wrote...
>>>>>>>>
>>>>>>>> John Larkin 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
>>>>>>>>> leveling loop with close to zero TC. All from 5 parts. Or sometimes
>>>>>>>>> six.
>>>>>>>
>>>>>>> What's the 6th part, I wonder?
>>>>>>
>>>>>>The peak detection can put a tiny flat on the negative swing of the
>>>>>>sine wave. A small resistor in series with the collector fixes that
>>>>>>and doesn't seem to do a lot of harm otherwise.
>>>>>>
>>>>>>>
>>>>>>>> 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?
>>>>>>
>>>>>>
>>>>>>But he didn't insult your wife, too.
>>>>>>
>>>>>>
>>>>>>> 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).
>>>>>>
>>>>>>
>>>>>>Oh, picky picky. It's actually, probably, a bit more complex, since
>>>>>>the emitter is a little negative at the instant of collision, and the
>>>>>>transistor is almost saturating, so some of the stolen base current is
>>>>>>going into the collector and some is going into the emitter. It would
>>>>>>be interesting to simulate, just to see where the currents really go.
>>>>>>Adding the collector resistor changes things, too.
>>>>>
>>>>>---
>>>>>So simulate it; I posted a working circuit list earlier if you can
>>>>>bear to use it without rancor getting in the way.
>>>>>---
>>>>>
>>>>>>But the AGC thing does work, and the TC is close to zero.
>>>>>
>>>>>---
>>>>>Serendipitous, no doubt, unless you intentionally designed it in.
>>>>>
>>>>>Did you?
>>>>
>>>>
>>>>Of course I did. As I noted, I needed a very amplitude-stable sinewave
>>>>source for the C5A inclinometer thing. This was a long time before DDS
>>>>and DAC versions were feasible.
>>>>
>>>>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.
>>
>> Crystal oven? What did 'Tek' and HP use on their scopes for a
>>reference?
>
>Why would that be amplitude stable?
>
>John

You use the oven to trigger the controlled oscillator.
From: John Fields on
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.

---
Then what's your problem?

From: BlindBaby on
On Thu, 10 Jun 2010 14:10:05 -0500, John Fields
<jfields(a)austininstruments.com> 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.
>
>---
>Then what's your problem?


That one might slip past a few of the folks here, including its target.
From: John Larkin on
On Thu, 10 Jun 2010 13:59:14 -0500, John Fields
<jfields(a)austininstruments.com> wrote:

>On Thu, 10 Jun 2010 09:01:11 -0700, John Larkin
><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Thu, 10 Jun 2010 09:09:55 -0500, John Fields
>><jfields(a)austininstruments.com> wrote:
>>
>>>On Thu, 10 Jun 2010 06:56:15 -0700, John Larkin
>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>On Thu, 10 Jun 2010 07:27:47 -0500, John Fields
>>>><jfields(a)austininstruments.com> wrote:
>>>>
>>>>>On Wed, 09 Jun 2010 21:01:19 -0700, John Larkin
>>>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>>>>
>>>>>>On Wed, 09 Jun 2010 16:02:57 -0500, John Fields
>>>>>><jfields(a)austininstruments.com> wrote:
>>>>>>
>>>>>>>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.
>>>>>>
>>>>>>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.
>

That's crazy. I sold stuff before Spice was invented. Maybe you did,
too.



>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.

Spice can be useful but, like breadboarding, it can devolve to
fiddling with a circuit until it seems to work.

John

From: John Larkin on
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