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Old 1st July 2012, 11:14 PM   #571
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Originally Posted by Edmond Stuart View Post
But I also need them as current sense resistors.
Hello Edmond,

I did test These and are very promising,
BTW, did You found the solution with the PCB soft already?

Cheers
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Old 2nd July 2012, 03:25 AM   #572
Krisfr is offline Krisfr  United States
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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.
How about 5 smd ONE ohm ONE watt resistors in parallel of the 1812 smd type or larger.
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Old 2nd July 2012, 04:14 AM   #573
Bonsai is offline Bonsai  Taiwan
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Quote:
Originally Posted by Edmond Stuart View Post
But I also need them as current sense resistors.
Edmond, is this for protection or are you needing to sense the current for feedback?
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Old 2nd July 2012, 09:26 AM   #574
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Originally Posted by wahab View Post
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.
Sure, but I've already bought a bunch of verticals.
If I had accurate models of laterals, maybe I would have go for laterals.
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Old 2nd July 2012, 09:28 AM   #575
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Originally Posted by PHEONIX View Post
Hello Edmond,
Are you going to use metal oxide types.
Regards
Arthur
Hi Arthur,
No. Just metal film or metal plate.
Cheers,
E.
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Old 2nd July 2012, 09:42 AM   #576
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Quote:
Originally Posted by Smiley 09 View Post
Hello Edmond,

I did test These and are very promising,
BTW, did You found the solution with the PCB soft already?

Cheers
Hi Smiley,

That were precisely the resistors that I was looking at, but at Farnell they are rather expensive: 3 euro incl. VAT.
Buerklin asks 2 euro, incl. VAT and shipment. That's more reasonable (though still a bit expensive).
Thanks for the hint!

>did You found the solution with the PCB soft already?
At the moment I'm playing with FreePCB and with the translation (export) from MicroCap to this PCB software.
It took me awhile to figure out how to do that. The trouble was how to specify a package of a capacitor and a resistor in MicroCap. The weird thing is that if you haven't first defined a (dummy) spice model for these components, exporting to PCB doesn't work, that is, the package definition is ignored.
Another concern is back-annotation, which is simply not possible.

Cheers,
E.
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Last edited by Edmond Stuart; 2nd July 2012 at 09:59 AM.
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Old 2nd July 2012, 10:15 AM   #577
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Originally Posted by Krisfr View Post
How about 5 smd ONE ohm ONE watt resistors in parallel of the 1812 smd type or larger.
That was my first solution. Since using 5 smd's is also a bit expensive and not the most elegant solution, I'm also looking for a single resistor alternative.
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Old 2nd July 2012, 10:24 AM   #578
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Originally Posted by Bonsai View Post
Edmond, is this for protection or are you needing to sense the current for feedback?
Hi Andrew,

Both. Actually, the purpose is threefold:
- Equalizing Id (ballast resistor)
- Protection (current limiting)
- Auto bias (current sensing)

Cheers,
E.
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Old 2nd July 2012, 10:33 AM   #579
PHEONIX is offline PHEONIX  Australia
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Originally Posted by Edmond Stuart View Post
Hi Arthur,
No. Just metal film or metal plate.
Cheers,
E.
Hello Edmond,

Unless you use a special metal film types (ones that fail open circuit) they can burn your PCB when they fail. MOX types fail open and have low inductance also that's why I use them.


Are you using Pads for your PCB layout software.

Regards
Arthur
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Old 2nd July 2012, 10:48 AM   #580
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Hi Arthur,

Why should they fail as they are already protected by an over-current limiter?

>Are you using Pads
Yes and no: I'm using FreePCB, that conforms to the PADS net-list format.

Cheers,
E.
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