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Old 14th November 2009, 04:53 PM   #2861
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Quote:
Originally Posted by ikoflexer View Post
Interesting; I'm thinking out loud here... with the buffer at the load, 2cm length of 1mm diameter wire amounts to about 14nH inductance, which, can be significant. Theoretically one should be better off with remote sensing, unless I'm missing something again?
Do you mean remote sensing phase shifts?
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Old 14th November 2009, 05:05 PM   #2862
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Quote:
Originally Posted by ikoflexer View Post
Interesting; I'm thinking out loud here... with the buffer at the load, 2cm length of 1mm diameter wire amounts to about 14nH inductance, which, can be significant. Theoretically one should be better off with remote sensing, unless I'm missing something again?
Hmmm. Not sure I get your point. My idea was to get the output stage (buffer) just a few mm from the load circuit. So the inductance of the load carrying wire is negligleable. The remote sense still has higher inductance but since that circuit is higher impedance the impact of the L is relatively lower. What do you think?

Edit: in my idea, the sense would still go back sveral inches to the control circuit (error amp, ref etc).

jd
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Old 14th November 2009, 05:06 PM   #2863
iko is offline iko  Canada
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Quote:
Originally Posted by Wavebourn View Post
Do you mean remote sensing phase shifts?
How bad can it be?
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Old 14th November 2009, 05:11 PM   #2864
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Originally Posted by john curl View Post
Actually the expert you are referring to, was just brought up, yesterday in fact, as one of the most 'clueless' of the group, here, by one of my references. I did not 'lead' the conversation, my source has read his papers.
I said expertS. And you don't know which I meant. I meant those people who have for the past several years not only given their position but backed it up with experiments and measurements. You and your 'references' have limited themselves to explaining when they had lunch together and what car they drive. Some references.

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Old 14th November 2009, 05:17 PM   #2865
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Quote without comment:'4.2.5 Interelectrode Parasitic Capacitances'
"Capacitance is a dynamic characteristic, as it is measured at a high frequency, generally 1MHz. For any FET, whether it is a SIT or a power MOSFET, we collect the various parasitic capacitances and identify them as Ciss, Coss, and Crss.
Each of these capacitances are complex, consisting of numerous parasitic elements. Furthermore, these capacitances are voltage-dependent, raising to high values at low voltages and frequently decaying to quite low values at high voltages. ... etc., etc."
Ref: Ed Oxner, one of my mentors.

Last edited by john curl; 14th November 2009 at 05:19 PM.
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Old 14th November 2009, 05:22 PM   #2866
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Jan, you are not being helpful, and if I try to 'help' you, you just sit on your duff and criticize my input, and indirectly the input of those who teach me. Why should they come here and waste their time debating what they have found important in audio over the last 50 years?
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Old 14th November 2009, 05:26 PM   #2867
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OK, first, would you like to debate Ed Oxner on the non-linearity of MOS or SIT input stages? This is the first stage in understanding the source of FM distortion in audio equipment.
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Old 14th November 2009, 05:31 PM   #2868
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Originally Posted by janneman View Post
Hmmm. Not sure I get your point. My idea was to get the output stage (buffer) just a few mm from the load circuit. So the inductance of the load carrying wire is negligleable. The remote sense still has higher inductance but since that circuit is higher impedance the impact of the L is relatively lower. What do you think?

Edit: in my idea, the sense would still go back sveral inches to the control circuit (error amp, ref etc).
jd
In my experiments the inductance and resistance of the remote sense leads had almost no significant effect (tested with about 15cm length), whereas a few cm of directly connected wire did have. This I tested in a real shunt reg with a sine wave load of about 56kHz. Before testing it for real I simulated the parasitic properties of the wire, somewhat exaggerated too, and the results were very good. Please don't be offended, I mention this for other beginners like me, who will benefit: it is essential to measure the voltage differentially at the load, V_positive-V_negative, and not V_positive - GND. I used the diff amp channel A-B on my ancient oscilloscope, at the 100uV/div, with probe A connected to V_positive and probe B connected to V_negative, and their grounds to the regulator ground.
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Old 14th November 2009, 05:45 PM   #2869
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Originally Posted by john curl View Post
Now, I see where you get your idea, however, you are still off, theoretically. Do you know what the transfer equation is for a V fet, or Static Induction Transistor (SIT)?
IDS = IDSS [1 (VGS / VP)]2


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Old 14th November 2009, 05:50 PM   #2870
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Quote:
Originally Posted by john curl View Post
Quote without comment:'4.2.5 Interelectrode Parasitic Capacitances'
"Capacitance is a dynamic characteristic, as it is measured at a high frequency, generally 1MHz. For any FET, whether it is a SIT or a power MOSFET, we collect the various parasitic capacitances and identify them as Ciss, Coss, and Crss.
Each of these capacitances are complex, consisting of numerous parasitic elements. Furthermore, these capacitances are voltage-dependent, raising to high values at low voltages and frequently decaying to quite low values at high voltages. ... etc., etc."
Ref: Ed Oxner, one of my mentors.
I was reacting to your post implying that feedback causes TIM, PIM, whatever as a blanket statement. Does Ed Oxner write somewhere that this is the case? Show us, if not, please stop trying to mislead us that the above has anything to do with that issue.

jd
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