Testing the TK Tar Baby

[Rosemary Ainslie]

TK,

Here is a shot of the FG current and M2 (Q2) Source current. Even though the M2 Source current has a higher negative peak current, the average current of both is about -182mA as shown.

Poynty - here's the thing.  We put our function probe directly on the Gate at Q1 (right) and the terminal (ground?) directly on the Gate at Q2.  Alternatively - we put that ground on the source rail - before the current sensing resistor.

I'm not sure that you're reading the right place with the ground positioning.

Regards,
Rosie

[poynt99]

We put our function probe directly on the Gate at Q1 (right) and the terminal (ground?) directly on the Gate at Q2.

Rosemary,

As do I. The FG connections are the same as in your first paper, but my diagram is drawn differently (I included the parasitic inductance in the Q2 Gate). My Q1 is on the left, but the connections (which is what counts) are the same.

[MileHigh]

Rosemary:

Poynty - here's the thing.  We put our function probe directly on the Gate at Q1 (right) and the terminal (ground?) directly on the Gate at Q2.  Alternatively - we put that ground on the source rail - before the current sensing resistor.

For starters, in order to avoid mass confusion, the right MOSFET, designated as "M2" in the schematic, is modelling what normally has been referred to as the "Q2 array."  Therefore "M1" on the left is modelling what has normally been referred to as "Q1."  I wish that everybody would stick to this terminology.

More precisely, what are you trying to measure?  You mention two measurements without stating what you are trying to measure and both of them look highly suspect.  But before commenting further please explain what you are trying to measure.

You have this horrible habit of not providing all of the required information when discussing circuits and measurements.  Review your prose before you post it and resolve the ambiguities.

Also, I can't tell you how many times we have read you making reference to (presumably) DC current passing through the gate input of a MOSFET.  This is annoying and tedious in the extreme.  One more nonsensical reference from you about DC current flowing through the gate input of a MOSFET and I will let you know in no uncertain terms.

All that being said, please make a new posting where you clearly describe what you are trying to measure and precisely where you place both terminals of your probe.

Also, use nomenclature that makes sense and is not ambiguous.  For example, for a battery you never say the "source" or the "source rail" or the "drain" or the "drain rail."  You say the negative and positive terminals, or the negative and positive rails.  That's just the way it is.  Stop mixing up battery terminology and MOSFET terminology.  You have been at this for years, and it's time for you to demonstrate that you are capable of learning and using the standard terminology that you yourself read every day.

MileHigh

[picowatt]

.99,

Regarding your sim schematic, is there a reason you chose position 4 instead of position 3 as the ground point?

I would think this would exclude the CSR and its inductance from the M2 feedback network.

PW

[TinselKoala]

@MH: 70,000 uF, not 700,000 uF. (71,000 actually.)  I wish....


I do have a 1 Farad cap.... at 3.5 volts.

And those "good" ceramics I have there are only 500pF and I only have about 20 of them.

But I'll manage somehow, probably.



So we still are having a lot of trouble getting Ainslie to understand that a Function Generator will provide current and in this circuit does act in series, either adding voltage (in the negative bias mode) or subtracting it (in the positive gate pulse mode) to that of the main battery. When the mosfet(s) are conducting there is a closed circuit for this power to flow, and it has a total DC resistance made up of the load, the battery's ESR, the CVR, the mosfet's Rds at the gate charge level seen, and the function generator's impedance. If this total resistance is on the order of 300 Ohms, with a battery voltage of 48 volts and a FG drive of 10-12 volts..... well, Do the Math (tm RA).

http://www.youtube.com/watch?v=q98QB6HTA6s

8 or 12 views even before I posted a link...... spooky.