Testing the TK Tar Baby

[TinselKoala]

Guys,
TK has just argued our point by showing that the Q2 Source leg is floating.

THAT IS NOT WHAT I HAVE SHOWN AT ALL. I HAVE SHOWN JUST THE OPPOSITE. YOU DON'T EVEN KNOW WHAT "FLOATING" MEANS.

Now he needs to argue is own argument.  Somehow.  Because what he needs to prove is that the flow of current from the battery can now move through the function generator itself. 

No, AINSLIE, you need to prove SOMETHING... anything.... by proper testing. I have shown that there IS current flowing... now you get your stuff together, your two video cameras and your fancy scope, and show that it IS NOT, by proper testing.

Through those probes.  And then the voltage would need to be greater than zero.  Not less than zero - which is evident in this phase of the oscillation.  It is an IMPOSSIBLE argument because the waveform evidence belies it.

Kindest as ever,
Rosemary

You idiot. You have no idea how to interpret your waveform evidence, which supports ME entirely.

READ THE AGILENT DOCUMENT ATTACHED TO THE POST.

"Because what he needs to prove is that the flow of current from the battery can now move through the function generator itself."

I HAVE PROVED THIS SEVERAL TIMES and I will do it again. What do you think is heating your load? Oh... you think it has got to be zipons since you can't believe WHAT THE EVIDENCE IS TELLING YOU , along with what all of us here are telling you, and the Agilent document is telling you.

Answer the questions in my quiz, if you think you are so smart.

[Rosemary Ainslie]

You idiot.

READ THE AGILENT DOCUMENT ATTACHED TO THE POST.

"Because what he needs to prove is that the flow of current from the battery can now move through the function generator itself."

I HAVE PROVED THIS SEVERAL TIMES and I will do it again. What do you think is heating your load? Oh... you think it has got to be zipons since you can't believe WHAT THE EVIDENCE IS TELLING YOU , along with what all of us here are telling you, and the Agilent document is telling you.

Answer the questions in my quiz, if you think you are so smart.

My dear TinselKoala - IF the function generator is discharging energy to heat the load then it would need to pass its energy through the battery supply and through the load itself and through the resistance of the function generator.  NOW how much energy is that function generating delivering?  DO THE MATH.

Rosie Pose

[picowatt]

Picowatt - I assure you.  The Gate leg of Q2 is connected to the Source leg of Q1.  The Source leg of Q1 is connected to the battery negative rail.  It is ONLY the source leg of Q1 that has the current sensing resistor in series with that negative terminal.  Q2 source leg goes NOWHERE.  It floats.  Q1's source leg is most assuredly negative - as you say - but it is negative ONLY when the Gate at Q2 is positive.  Then.  The Source leg of Q2 is connected to the Gate of Q1.  The source leg of Q2 is absolutely not connected to anything other than the Gate at Q1.  Please look again at the NERD schematic and then look again at my diagram of the connection points.  Because that configuration is a fact.  And that is most certainly how those legs are LITERALLY connected to each other.  And that the Q2 Source leg is floating is also evident on a view of those photos of the circuit board.  And it is and will be easily evidenced when we do our demos.  I do not know if that's how TK has configured his circuit.  It most certainly is how we've configured ours.

For the battery to be able to discharge any current through Q2 during the 'off' period of each switched cycle it would not be able to discharge that positive current flow through its source leg and onto the Gate at Q1.  The blocking diode at Q1 opposes a positive flow of current.  It would effectively leave the circuit open.  The resulting positive current flow - from the battery - assuming that there was any - would need to move through the function generator's terminal to it's probe and then onto the Source leg of Q1 and then only onto the source rail of the battery supply - literally THROUGH the function generator probe and terminal.  Then it would need to resolve as a positive current flow.  Above zero.  And typically - the current from the battery supply needs must pass from the Drain leg of Q2 to the Source leg of Q2 before it can go anywhere at all.  The voltage at this point in the switching cycle is NEGATIVE.  So clearly it is NOT coming from the battery supply.  Quite apart from which that battery supply would also then need to be discharging a negative current flow evident in that negative voltage during that 'off' period of each duty cycle.  Which is impossible.  One could argue that the voltage is weakening during that switching cycle - and that capacitance from the MOSFETs kick in.  Then there would be a reversal of that voltage.  But there is way too much current to be accounted for by capacitance.  So where does that really robust current flow come from?  If that current flow is indeed able to pass through the function generator's probe and terminal - then the strength of that current flow - as mentioned - is far greater than the capacitance that is available at the MOSFETs and far greater than the level of applied voltage that is measured across those switches.

Rosemary-I assure you.

I quote you from above, "The gate leg of Q2 is CONNECTED to the source leg of Q1.  The source leg of Q1 is CONNECTED to the battery negative rail" (via the CSR).  Parenthetical and emphasis added

Therefore, the source leg of Q1 AND the gate leg of Q2 are ALWAYS at the same potential, they are, afterall, CONNECTED.  The potential to which they are both CONNECTED is at or very near the battery negative rail.

Therefore, the voltage at the source leg of Q1 AND at the gate of Q2 is ALWAYS at or very near ground, which is the battery negative rail.  Again, the gate of Q2 is always at or near ground potential.

(As they are actually connected to the non-battery end of the CSR, they will always be at the same voltage as is measured at the non-battery end of the CSR, which is near ground potential)

The function generator CANNOT apply a positive voltage directly to the gate of Q2, as the gate of Q2 is ALWAYS connected to the negative rail (ground) via the CSR (as is the source of Q1).

The function generator outputs a voltage that is either positive or negative with respect to the FG's signal common (the signal common being the function generator's BNC connector outer metal contact, typically the black lead on a BNC cable with clip leads).

The function generator signal common is CONNECTED to GROUND and is therefore ALWAYS at ground potential (or the CSR voltage depending on its connection point).  The FG signal common does not change polarity, only the function generator's output signal changes polarity (the FG output signal is the BNC center contact, typically red clip lead on BNC cable).

The source leg of Q2 is connected to the battery negative rail (or CSR) by way of the function generator.  When the function generator output is a negative voltage, the negative voltage applied to the source leg of Q2 causes Q2 to partially turn on and the current that ensues flows through the source leg of Q2 and the function generator to the battery negative rail via the CSR.

I suggest you spend some time understanding this, you now argue against even the most obvious,

PW

[picowatt]

My dear TinselKoala - IF the function generator is discharging energy to heat the load then it would need to pass its energy through the battery supply and through the load itself and through the resistance of the function generator.  NOW how much energy is that function generating delivering?  DO THE MATH.

Rosie Pose

Approximately 200ma.  We did the math, TK made the empirical measurement.

[TinselKoala]

My dear TinselKoala - IF the function generator is discharging energy to heat the load then it would need to pass its energy through the battery supply and through the load itself and through the resistance of the function generator.  NOW how much energy is that function generating delivering?  DO THE MATH.

Rosie Pose

It is indeed doing just that. YOU DO THE MATH, you idiot hypocrite. The FG is adding its power to the system when it is hooked up as shown. How else can you explain the fact that A BATTERY CAN BE SUBSTITUTED FOR THE FG and the circuit functions identically, until THIS BATTERY RUNS DOWN?