[danlaix]

Here are the specs:

Type Pd mx/W Vdg mx/V Vdss mx/V Idss mn/mA Igss mx/nA
2N5486 0.31 25.00 25.00 8.00 1.00

2N5459 0.31 25.00 15.00 4.00 -
2N5457 0.31 25.00 15.00 1.00


can i use these 2 for Q1 and Q2?
As in Q2 = 2N5486 Q1 = 2N5459

I couldnt get 2N5484 here...

 

[tangent]

If you use a source resistor on the lower JFET (like in the PPA), then yes, you can. You use that resistor to adjust the current through the cascode. Without that resistor, you'll probably end up with too much current through the cascode; you'll warm up the chip and make its performance worse.

EDIT: If you can't use a source resistor, try looking for a 2N5457. It's similar in specs to the 5484.

 

[danlaix]

Quote:

EDIT: If you can't use a source resistor, try looking for a 2N5457. It's similar in specs to the 5484.

Tangent, in other words, if i dun use any source resistor, I can use 2N5486 for Q2 and 2N5457 for Q1?

Another question is that, in my Meta42, I used 2N5486 for Q2 and 2N5484 for Q1, and i add a source resistor to R10. Should i removed the R10 instead?

 

[tangent]

Quote:

if i dun use any source resistor, I can use 2N5486 for Q2 and 2N5457 for Q1?

Yes, although even better would be to get a bag of 2N5457s, sort them by Idss, and pick pairs from that. If you're going to use dissimilar JFET types, you should still use a source resistor.

Quote:

i add a source resistor to R10.

The META42's R10 is not a source resistor. I mean Rs in my class A biasing article.