Testing the TK Tar Baby

[picowatt]

Voltages are relative, though. It is clearly possible for a voltage to be applied that is "below" or more negative than the signal ground, as your SPDT switch example proves. Then, if one attached the negative lead of a voltmeter to that more negative voltage, the signal ground would be positive with respect to it, and if you put a circuit element in there, current would flow in the proper conventional direction wrt the signs of the measurement. How's that for clouding the issue?

The voltage at the (FG signal ground-system ground-Q2 gate) never changes potential, that is true, but "voltage" is potential with respect to-- or reference to-- another potential. What happens is that the "other" FG wire swings positive _ and negative_ with respect to that fixed reference level. So if you have your voltmeter's negative lead hooked to the signal ground, it will appear to indicate both positive and negative polarities as the other lead swings.So when you are applying a voltage to the Q2 source that is more negative than the common ground (where the Q2 gate is hooked up), that makes Q2's gate _positive with respect to Q2's source_ even though that point is pinned to the system and signal ground potential. The transistor then moves in and out of the linear conductance region as the FG's negative signal to the source (hence the positive relative signal to its gate) fluctuates around that 4 volt potential difference level during the oscillations. (Of course here we are treating the csr as if it weren't there or that the FG's ground is connected as in the demo video, not the schematic.)

We are both describing the same thing, and agreeing about it, but just from different perspectives.

TK,

This is indeed all true, but first "someone" must first see that a negative voltage is applied to the Q2 source.  THEN, it can be discussed how a negative voltage applied to the Q2 source is similar to applying a positive voltage to the gate of Q2.

Q2 does not care if its gate is made more positive with respect to its source, or if its source is made more negative than its gate.  As long as the gate voltage relative to its source is a positive value in excess of Vth, Q2 will turn on.

Again, I know you know this.

I see that a replicator "over there" is having a bit of trouble with a 555 heating up.  She claims she never had this problem, as if she ever attempted operating the NERD circuit on a 555 like you did.  I wonder if the replicator is even applying a negative voltage during that portion of the cycle.

If so, can we say "bias current"?

PW

[picowatt]

TK,

And for clarity, she already seems to believe that the FG signal common is literally changing polarity and (somehow) directly applying a positive voltage to the Q2 gate.  She is not speaking relatively so.  She has made this clear in several of her posts.  Therefore, I am attempting to be very clear regarding the FG signal common always remaining at the same voltage as the non-battery end of the CSR.  The only polarity changing, is that of the FG output, as referenced to the FG signal common and the non-battery end of the CSR to which the FG common is connected.

PW

[picowatt]

TK,

This is indeed all true, but first "someone" must first see that a negative voltage is applied to the Q2 source.  THEN, it can be discussed how a negative voltage applied to the Q2 source is similar to applying a positive voltage to the gate of Q2.

Q2 does not care if its gate is made more positive with respect to its source, or if its source is made more negative than its gate.  As long as the gate voltage relative to its source is a positive value in excess of Vth, Q2 will turn on.

Again, I know you know this.

I see that a replicator "over there" is having a bit of trouble with a 555 heating up.  She claims she never had this problem, as if she ever attempted operating the NERD circuit on a 555 like you did.  I wonder if the replicator is even applying a negative voltage during that portion of the cycle.

If so, can we say "bias current"?

PW

TK,

It is truly a shame if her only replicator "over there" is a neophyte to electronics and being "lead by the blind" as it were regarding her skills in the art. 

It seems doubtful that a negative voltage is being applied to the NERD circuit using a 555 in his replication during the equivalent FG output LO period.  As you can attest to, a simple "standard" 555 circuit operating on a single supply cannot emulate the FG settings.  It is a bit more difficult.

Possibly I missed somethng, has she ever presented a circuit showing the NERD circuit operating from a 555?

It just goes on and on...

PW

[picowatt]

Dear readers,

I highly suggest all read her post 41 "over there" (I believe it was 41, a response to .99).  It explains in more inaccurate detail why she "believes" that the 'scope must be AC coupled.  If the 'scope is DC coupled, she says the voltage at Q2 remains "zero".  From this, I assume she means that the voltage at the gate of Q2 remains at zero, which it precisely does (or moreso precisely, it remains at the voltage of the non-battery end of the CSR).  She knows this cannot be, as the FG is set to output a negative voltage during its LO period, so she thinks that merely switching the 'scope to AC solves this dilemma. 

The entire post is nothing but unintelligent gibberish.  I do not know who "advises" her, but they are either very wrong, misunderstood, or just plain imaginary.

Her post is good for chuckle though... if it weren't so sad at the same time.

PW

[TinselKoala]

TK,

And for clarity, she already seems to believe that the FG signal common is literally changing polarity and (somehow) directly applying a positive voltage to the Q2 gate.  She is not speaking relatively so.  She has made this clear in several of her posts.  Therefore, I am attempting to be very clear regarding the FG signal common always remaining at the same voltage as the non-battery end of the CSR.  The only polarity changing, is that of the FG output, as referenced to the FG signal common and the non-battery end of the CSR to which the FG common is connected.

PW

Yep, it's clear enough to me, that is for sure. But we've seen how flailing and wallowing about muddies the waters and even the clearest explanations get twisted around in Ainslie-space. I'll just let you make your point your way, but I've done some FG output videos, as usual, that attempt to illustrate what you mean.

After all, one could simply hook the FG's "ground" lead (black output clip) to a big  honking cold water pipe, and then it should be perfectly clear to ANYONE , even YKW, that the potential at that point is always at Earth Ground.... you'd be hard pressed to change _that_ potential level by any means available to Ainslie. Yet, her circuit will operate just as it always does, even though it is now clearly impossible for the FG's negative output lead to change potential.

I have a 6 foot length of 1/2 inch copper pipe driven deep into the wet soil underneath my window air conditioner's overflow drip, with a 14-ga stranded lead-in wire to my workbench, that is my Earth system and RF ground when needed. You can bet your next three lunches that _that_ point isn't gonna let its potential be changed by no smoking FG, not even the Interstate.