Matching Aleph 30 mosfet

[same]

hi,
for match mosfet is better use the source current that is in real life.
Than, is correct testing input mosfet with 12mA and power mosfet with 670 mA?
giorgio

[wuffwaff]

yes,

William

[h_a]

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

[EUVL]

> 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

[wuffwaff]

Hi,

as far as I understood the 12mA and 670mA are the real circuit values.

William

[Nelson Pass]

Originally posted by EUVL
The fact that 2 transistors have the same Vgs at one current does not guarantee they are identical in their Vgs vs Id characteristics.

True, although not a big issue. To minimize this, use devices
from the same lot code as well - they tend to be more identical
given the matched Vgs.

[EUVL]

I agree; but this applies more to the IRF parts than other MOSFETs, e.g. Toshiba (both MOSFETs and JFETs).


Patrick

[Babowana]

Originally posted by EUVL


I agree; but this applies more to the IRF parts than other MOSFETs, e.g. Toshiba (both MOSFETs and JFETs).


Patrick

Okay . . . which Power MOSFETs of Toshiba are best useful?
Meanwhile, I liked Hitachi 2SK135 and 2SJ50 times ago.

[EUVL]

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

[same]

Originally posted by wuffwaff


as far as I understood the 12mA and 670mA are the real circuit values.

I think that are real circuit values but maybe is not so.
Hannes say that correct values are 10 mA and 500mA.
It's ok?
giorgio