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Old 30th June 2012, 02:20 PM   #561
Bonsai is offline Bonsai  Taiwan
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Quote ". . . , for (the sake of ) the pope s balls...."

LoL! :-)
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Old 30th June 2012, 02:30 PM   #562
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Quote:
Originally Posted by Edmond Stuart View Post
In addition, I've changed the frequency compensation of the OPS to a 2nd order
The loop around the OPS (Fig 12c) showed conditional stability. You have moved to second order to improve the stability?
Also curious about Fig 7. Why the low frequency roll-off?
And a last one for today - in Fig. 12 C22 and C23 could be combined and tied to point OPSIP in a natural way. Any reason to use 2 capacitors?

Best wishes.
David

BTW in Dutch we say: 'voor de kat z'n kut' In polite conversation?
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Old 1st July 2012, 04:20 PM   #563
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Default compensation details

Quote:
Originally Posted by Dave Zan View Post
The loop around the OPS (Fig 12c) showed conditional stability. You have moved to second order to improve the stability?
At the same time time I've increased the time-constants of the OPS compensation somewhat. As a result, the PM is about the same, while the distortion is decreased by ca. 40%. Notice that this kind of compensation differs from Miller or TMC. Should we call it 'feed-forward compensation' (comparable to the compensation in Bob's HEC-OPS)?
RC5 and CC5 define the second order response, but at the same time CC5 also provides some phase lead.

Quote:
Also curious about Fig 7. Why the low frequency roll-off?
What you see there is the local loop gain of the Miller compensation (the lower the frequency, the higher the impedance of the Miller caps, the lower the loop gain, hence...).

Quote:
And a last one for today - in Fig. 12 C22 and C23 could be combined and tied to point OPSIP in a natural way. Any reason to use 2 capacitors?
The intention here is that the Miller caps (C19 & C20, see pic below) are directly connected to the output of the TIS buffers, i.e. to the emitters of Q21 respectively Q22. Tying them somewhere in the middle of the OPS compensation network is not a good idea.

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Best wishes.
David

BTW in Dutch we say: 'voor de kat z'n kut' In polite conversation?
(literally: 'for the cat his cυnt')
In the presence of our queen, I wouldn't use those words.
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Old 1st July 2012, 07:17 PM   #564
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To all,

BTW, does anybody know where to buy reasonably priced low inductive 5W SMT resistors between 0.2 and 0.3 ohm (preferable 0.22 ohm)?

Cheers,
E.
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Old 1st July 2012, 07:28 PM   #565
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nl.mouser.com? Just looked and they have a reasonable selection in your stated power and resistance range. I guess it depends what you mean by "reasonably priced"; I find these low-ohm power SMT resistors to be surprisingly expensive (i.e. I spend more on Re resistors than I do on output transistors!)
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Old 1st July 2012, 07:33 PM   #566
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>I spend more on Re resistors than I do on output transistors!
That's exactly the trouble.
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Old 1st July 2012, 08:00 PM   #567
wahab is offline wahab  Algeria
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That makes Renesas laterals quite more competitive since you can
parralel them straight on , without any source resistors..
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Old 1st July 2012, 08:15 PM   #568
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But I also need them as current sense resistors.
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Last edited by Edmond Stuart; 1st July 2012 at 08:26 PM. Reason: resistor -> resistorS
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Old 1st July 2012, 08:27 PM   #569
wahab is offline wahab  Algeria
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That was to be expected...

Never mind , laterals are friendly devices , the current is in proportion of Vgd ,
wich vary at a 1V/A/Device rate or so (Gm = 1S) , just take the sensing point before the gate resistor.
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Old 1st July 2012, 08:48 PM   #570
PHEONIX is offline PHEONIX  Australia
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Quote:
Originally Posted by Edmond Stuart View Post
To all,

BTW, does anybody know where to buy reasonably priced low inductive 5W SMT resistors between 0.2 and 0.3 ohm (preferable 0.22 ohm)?

Cheers,
E.
Hello Edmond,

Are you going to use metal oxide types.

Regards
Arthur
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