Testing the TK Tar Baby

[picowatt]

picowatt -

Regarding the flow of current through the function generator - here's what you ACTUALLY wrote.I take it that you're arguing that the positive bias from the function generator (FG) that's applied to the gate of Q2 enables a flow of current from the battery supply source?  This current flow then passes through the FG probe.  Then it passes out of the ground terminal of that probe to the source rail of the battery supply. Or to put it as Poynty Point prefers - to the battery's negative terminal?  Therefore does the battery REMAIN connected.  And therefore is there no significance in that oscillation.  Is that your argument? Because then, the short answer is 'NO'.  It is not possible.  So WHY should I need to 'understand it'?

Then you continue - in that same post...IF the gate at Q2 allowed any current from the battery supply to pass through the FG probes and to its ground terminal then it would also need to be passing a current from the battery that would reflect above zero.  In effect - either Q1 or Q2 would be continually ON.  Therefore the current sensing resistor (CSR) (NOT CVR as TK keeps putting it)) would NEVER record a voltage less than zero.  At best it would would show a small fluctuation at the point at which the signal changes to apply a positive bias first at Q1 and then at Q2.  Which then may result in that voltage trending to zero.  But it would never CROSS zero.  EVER.  Whereas, in point of FACT what we see is that when the signal transfers - then the voltage across the CSR ACTUALLY swings to a NEGATIVE voltage.  Unless, of course, you're arguing that the battery is now discharging a current from the DRAIN rail as an applied negative voltage.  Perhaps?  In which case we do, indeed, have extraordinary batteries.  And we would also need to have rather EXTRAORDINARY transistors.  Because then they would also need the rather improbable property of enabling an entirely IMPOSSIBLE negative current from the battery Drain rail.  And all this notwithstanding the applied positive signal at the gate of Q2. So. Here's my answer. NO.  It is not MY 'lack of understanding regarding this circuit's operation and how a function generator operates'.  And if it's not mine is it perhaps your own lack of understanding?  I'm sure you won't consider the suggestion insulting, as you were well disposed to apply it to me.

So again.  When you presume to write this...rather - I put it to you that one 'hopes' that it is YOU who would have had a better understanding.  The more so as you are 'posing' - if not as an expert - as a competent engineer in the analysis of current flow.  Certainly you went to some pains to advise us all that a person of your standing could simply 'read' all that he needed to 'read' from an oscilloscope trace.  Why then are you NOT seeing this?  Why do you NOT know how the voltage across the CSR would resolve IF, indeed, the battery was discharging current through the Gate of Q2?  Bear in mind picowatt.  I'm the amateur.  Yet even I know this.  And I can't comment about our readers.  But I certainly know that not you, nor TK, nor MileHigh, nor Farmhand, nor PhiChaser has mentioned this.  WHY?  Are you relying on our readers' ignorance?  Are you assuming an entire lack of intelligence in everyone who engages here - directly or indirectly?  Or are you even aware of the ACTUAL 'thing' that we're pointing to?  WHAT?  Because whichever way one reads these statements - in the final analysis if you ARE aware of these points, then it is nothing short of insulting.  Or had you simply overlooked this?  It can only be one or the other.  So. Do let us know.

./...

Rosemary,

I read the very first paragraph you wrote, and it is again nothing but a twisting of my words and further demonstration that you must not read what is written or twist words as a tool for arguing.  I never once discussed a positive voltage applied to the source in the post you reference.  Yet again, you claim that to be what I ACTUALLY wrote (you're emphasis).  Again, when the FG applies a negative voltage to the source of Q2, Q2 is biased on and current flows thru Q2 and the FG.  I have said it several times and yet you continue to want to twist it into something else.  If you  do not understand what I am writing or how a function generator works, by all means feel free to ask and DISCUSS (my emphasis), but please do not tell me what I am ACTUALLY saying or put words in my mouth.  It is rude, disrespectful, and not at all professional.

Its a wonderful day outside and I really do not feel like playing word games or seeing my words twisted about right now.  Assuming the rest of your posts are similar to your very first paragraph, I choose to read no more of your posts at this time.

Have a nice day, I am...
PW

 

[picowatt]

OK....sorry about the confusion earlier. I misread the timebase on Fig 4 for a minute.

The answer is "yes, pretty much". The similarity at slower timebase settings during pulsating drive with negative gate pulses I've shown lots of times including above.

Here's a shot showing the similarity to Fig4:

Timebase 1 microsecond per division showing the higher frequency of just under 2 MHz.

A channel (lower) is the voltage across the CVR at 2 volts per division, B channel (upper) is the voltage at Q2 source or FG+ as I prefer to call it at 5 v/div (I couldn't get a stable trigger at 10 V/div. Zero references are the closest graticule line to the grey marks on the right side of the bezel.

TK,

OK, now we're talking.  Timebase, zero ref, and V/div included.  Were these shots taken with the 10R and pot for a bias source?

As you can see, there are little nuances on Rosemary's CH3 traces (FIG4) that are absent.  Her circuit demonstrates several plateaus that yours does not.  I would again suggest using the FG or pwr supply and 50R to see what if any differences show up.  Also, alternate scope shots with the bias supply ground (or FG gnd) tied to either end of the CSR may help weed out the differences between the CH3 trace in FIG4 and FIG5 of the first paper.  Keep in mind that some of the FIG4 plateaus may be related to the Q1 issue indicated by FIG3.

PW

[Groundloop]

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[picowatt]

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Groundloop,

Your very nicely done drawings will hopefully enlighten.

I do have a couple of conditions to add.  When the FG is -12volts, the voltage at the source of the MOSFET will only pull to -3 to -4 volts (the threshold/turn on voltage of the MOSFET), so the drop across the 50R will be closer to 8 to 9 volts and not the full 12 volts.  The current/wattage dissipation then needs to be recalculated accordingly.

Also, during the oscillation, the MOSFET will be cycling between an increase and decrease current, so the bias current will modulate as well.

I greatly appreciate your time in drawing and posting this.  It is an excellent and concise representation of how the function generator is being utilized, and of the current flow through the function generator and the MOSFET.


Thanks!

PW

[TinselKoala]

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Bingo.

Well done.

Unfortunately some people still deny that the FG can function as a power source or allow current from the main battery to flow through it, despite several demonstrations from me, the technical analyses by .99, MileHigh, PicoWatt and even Stefan Hartmann himself in addition to technical publications from Agilent and Tek...... yet she still denies it and calls us all incompetent because we believe such an idiotic thing to be true.
No... she doesn't make personal attacks at all, does she.

And she makes it even worse, by admitting that she's a rank clueless ignorant amateur, so how much stupider WE must be since we believe so many things that Rosemary has taught us aren't true at all.

Like Quantum Electrodynamics, standard physics, electrical power measurements, and the operation of mosfets. All these things, that we have been using for all these years to do things like design digital oscilloscopes and video cameras and spacecraft... all these things are false, because Rosemary has a "thesis" that needs proving.

Oh.. and there's this:

http://www.bing.com/search?q=current+viewing+resistor&form=MOZSBR&pc=MOZI

(Another bogus claim of RA easily refuted, yet another thing that she is wrong about but won't admit or correct.)

And you  know what... I could call the CVR "Charlie" or a Red Elephant or the Rock of Ages Incarnate... and it would still make the SAME READINGS on an oscilloscope.