Matching Aleph 30 mosfet

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Since the input fets are biased with 10mA and the output mosfets with about 500mA I would say that your ordinary matching at 12mA and 670mA is perfectly fine.

Matching even closer to the real circuit values won't bring substantial benefit, but of course would be ideal.

Cheers, Hannes
 
> Matching even closer to the real circuit values won't bring substantial benefit, but of course would be ideal.

I dare to disagree.

The fact that 2 transistors have the same Vgs at one current does not guarantee they are identical in their Vgs vs Id characteristics. If you measure enough over full range, you would know what I mean. Also the thermal sensitivity does vary (i.e. room temperature match does not guarantee match at working temperature.)

Would the amp work ?
Yes. But it would not have the minimal distortion that a full-range match under working conditions would give you.


Just my 2 cents,
Patrick
 
I use 2SK1529 to replace IRFP240, but you need to change something to suit the lower Vgs. There is also a complememnntary part 2SJ200.

Similarly, 2SK1530/2SJ201 can replace IRFP250/9250 with adaptation. Then there are 2SK2013/2SJ148 which are similar to IRF610/9610, again with adaptation.

The list is endless ......


Patrick
 
EUVL said:
> The fact that 2 transistors have the same Vgs at one current does not guarantee they are identical in their Vgs vs Id characteristics.

I did a regression analysis of transconductance vs Vgs -- for lateral MOSFET's and HexFETs -- there is a very high correlation if the devices come from the same lot code -- will pull up the data when I get back to NJ with a histogram.
 
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