MOSFET matching for BOSOZ

Ren · 9th February 2003, 04:21 PM

NP stated that the BOSOZ design does not strictly require matching of the MOSFET pairs. But I decided to order extra parts and match them, just to learn.

I used the procedure in the PassDIY article, except that my available power supply is +12V, not the +15V described. I used a 1.6K resistor to keep the 5 mA current described by NP with my +12V. I made my measurements, and selected the best-matched pieces. So far, so good.

Then I noticed a statment in the BOSOZ article: each MOSFET will pass 40 mA in operation. Does that mean that the matching needs to be done with 40 mA of current to be correct?

Ren

ElectroNick · 9th February 2003, 05:23 PM

H Ren,

I matched those mosfets also. I found that the Vgs varies when temperatures change. So for a few seconds i used a Ids of approx 100mA to heat the mosfets. Then i switched to the 40 mA like the articles says. Next thing i did was wait (for 10 or 15 minutes) so that the temperature of the heatsink and FET's dropped to normal.

By doing so i could make pairs of FET's with only 1 mV difference.

You'll need a few hours of free time to do it

Good Luck,
Nick

Nelson Pass · 9th February 2003, 07:29 PM

If you want to be medieval about your matching,
you will use the same currents as the application,
but a lot of the time you'll find that that matching
at 5 ma tracks well enough to get you a decent
match at 40 ma, so I wouldn't worry.

There is so much resistance in series with the Sources
on BSOZ, that it doesn't matter much in any case.

deming8418 · 11th February 2003, 11:51 AM

Hi ,Nelson!Nice to see you throug the net.
Last year I had tested ablout 100 pieces of irf9610s with the method on web passdiy.com. The difference between the mosfets is small, the biggest tolerance is less than 10mv.I'm sure ,it's true.Through the test I got 8 couple of mosfet.In December I'd made the Aleph3. The DC offset of the both channels is around 60mv.In despite of very much effort I paid ,it i was no use.I cann't understand it. Recently I want to built the Aleph X. Is there any better way to match the irf9610?Any suggestion will be apreciated.
THX to Nelson .

9th February 2003, 04:21 PM	#1
Ren diyAudio Member Join Date: Apr 2002 Location: Northern Virginia	MOSFET matching for BOSOZ NP stated that the BOSOZ design does not strictly require matching of the MOSFET pairs. But I decided to order extra parts and match them, just to learn. I used the procedure in the PassDIY article, except that my available power supply is +12V, not the +15V described. I used a 1.6K resistor to keep the 5 mA current described by NP with my +12V. I made my measurements, and selected the best-matched pieces. So far, so good. Then I noticed a statment in the BOSOZ article: each MOSFET will pass 40 mA in operation. Does that mean that the matching needs to be done with 40 mA of current to be correct? Ren

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9th February 2003, 05:23 PM	#2
ElectroNick diyAudio Member Join Date: Dec 2002 Location: The Netherlands	H Ren, I matched those mosfets also. I found that the Vgs varies when temperatures change. So for a few seconds i used a Ids of approx 100mA to heat the mosfets. Then i switched to the 40 mA like the articles says. Next thing i did was wait (for 10 or 15 minutes) so that the temperature of the heatsink and FET's dropped to normal. By doing so i could make pairs of FET's with only 1 mV difference. You'll need a few hours of free time to do it Good Luck, Nick

9th February 2003, 07:29 PM	#3
Nelson Pass The one and only Join Date: Mar 2001	If you want to be medieval about your matching, you will use the same currents as the application, but a lot of the time you'll find that that matching at 5 ma tracks well enough to get you a decent match at 40 ma, so I wouldn't worry. There is so much resistance in series with the Sources on BSOZ, that it doesn't matter much in any case.

11th February 2003, 11:51 AM	#4
deming8418 diyAudio Member Join Date: Dec 2002 Location: Hangzhou,Chian	Hi ,Nelson!Nice to see you throug the net. Last year I had tested ablout 100 pieces of irf9610s with the method on web passdiy.com. The difference between the mosfets is small, the biggest tolerance is less than 10mv.I'm sure ,it's true.Through the test I got 8 couple of mosfet.In December I'd made the Aleph3. The DC offset of the both channels is around 60mv.In despite of very much effort I paid ,it i was no use.I cann't understand it. Recently I want to built the Aleph X. Is there any better way to match the irf9610?Any suggestion will be apreciated. THX to Nelson .

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