Matching Mosfet's

Jena · 3rd April 2004, 10:51 AM

Hello Fellows technicians.............

I'm wondering one things about the matching mosfet's.

I have read a lott in terms of this matter but there is a little bit opinions in terms of how many times you need for match mosfets.

Somebody said take less 1 minutes and write on the stick label a value.

Others said take for 10 minutes and write on the stick label the value.

But for my experience when myself matching the IRFp244 with 10 ohm resistance the VGS value it is not stable.

The same for IRF9610.

There is somebody that give me a right solutions and how I'll match correctly the Mosfet's it should appreciated a schematic for mosfets 244 and 9610.

Thanks in advance for an answer.

dantwomey · 3rd April 2004, 01:56 PM

This topic has had alot of prior discussion. Have a look at this thread "Fuzzy on FET Matching". And, have you read Practical Mosfet Testing for Audio at the Pass DIY website?

Regards,
Dan

batee · 4th April 2004, 04:57 AM

I found that the size of the heatsink affected this *a lot*.

Last month I was matching some IRF610s with Ids of ~2A.

I noticed that when I had a small heatsink attached (<4in^2), they continued to climb in temperature over the next 30 minutes, and Vds changed accordingly.

When I had a large heatsink (240in^2) attached, they stayed relatively cool over the next 30 mins and Vds was much more stable.

In all cases, I waited until the fourth digit to the right of the decimal (the 100uV digit) stopped changing, then decided that was good enough.

Mad_K · 5th April 2004, 05:23 AM

I use 10 seconds (recommended by Nelson) and are getting very good matches

jwb · 5th April 2004, 06:23 AM

I attach them to a heater. You want them operating at steady state. You could also plot Vgs versus temperature, or Vgs versus current, or both. The more sophisticated your matching technique, the better match you will get.

Also I recommend loading them with a current source instead of a resistor.

3rd April 2004, 10:51 AM	#1
Jena diyAudio Member Join Date: Mar 2004 Location: London	Matching Mosfet's Hello Fellows technicians............. I'm wondering one things about the matching mosfet's. I have read a lott in terms of this matter but there is a little bit opinions in terms of how many times you need for match mosfets. Somebody said take less 1 minutes and write on the stick label a value. Others said take for 10 minutes and write on the stick label the value. But for my experience when myself matching the IRFp244 with 10 ohm resistance the VGS value it is not stable. The same for IRF9610. There is somebody that give me a right solutions and how I'll match correctly the Mosfet's it should appreciated a schematic for mosfets 244 and 9610. Thanks in advance for an answer.

5th April 2004, 05:23 AM	#4
Mad_K diyAudio Member Join Date: Sep 2002 Location: Norway	I use 10 seconds (recommended by Nelson) and are getting very good matches __________________ Mads K

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3rd April 2004, 01:56 PM	#2
dantwomey diyAudio Member Join Date: Feb 2002 Location: Canada	This topic has had alot of prior discussion. Have a look at this thread "Fuzzy on FET Matching". And, have you read Practical Mosfet Testing for Audio at the Pass DIY website? Regards, Dan

4th April 2004, 04:57 AM	#3
batee diyAudio Member Join Date: Mar 2004 Location: Rolla, MO	I found that the size of the heatsink affected this a lot. Last month I was matching some IRF610s with Ids of ~2A. I noticed that when I had a small heatsink attached (<4in^2), they continued to climb in temperature over the next 30 minutes, and Vds changed accordingly. When I had a large heatsink (240in^2) attached, they stayed relatively cool over the next 30 mins and Vds was much more stable. In all cases, I waited until the fourth digit to the right of the decimal (the 100uV digit) stopped changing, then decided that was good enough.

5th April 2004, 06:23 AM	#5
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	I attach them to a heater. You want them operating at steady state. You could also plot Vgs versus temperature, or Vgs versus current, or both. The more sophisticated your matching technique, the better match you will get. Also I recommend loading them with a current source instead of a resistor.

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