F5X -- the EUVL Approach - The Build Thread

[NicMac]

Although I should allow you to enjoy your achievements I can't help to show where I am....
In blue the calculated Idss/Yfs of the 2SJ74 after 5R1 degeneration.

[EUVL]

Nice figure.
Shows clearly that my guestimation 5R1 is near spot on !!!!




Patrick

[NicMac]

Of course your 5R1 value was chosen for a reason like most things you do

For my FETs I actually find 5R6 and 6R2 to be a bit better. As computing cost little I in the end actually used 7 different Rdeg (4R3, 4R7, 5R1, 5R6, 6R2, 6R8 and 7R2) to generate a virtual set of 2723 degenerated 2SJ74's (see figure) and used these for matching. With those I obtained 42 NNNNPPPP-sets with 0.5% tolerance for both Idss and Yfs. This is a yield of about 43% for the 2SJ74.

Of course there is the downside that each 2SJ74 will need a different Rdeg. But as a DIY'er I can live with this minor logistic complication.

Obviously Oneclock has measured matches while mine are calculated and should to be verified experimentally. I nevertheless trust the practical validity of the equations some kind person provided me with

Where is that F5X Pre?

Cheers,

Nic

P.S. Note how increasing Rdeg pushes both Idss and Yfs down posing a limit to what can be achieved in terms of matching. Using 100 different Rdeg's values would in fact not increase yield notably. Many 2SJ74 will never match because they have to low Idss.

[EUVL]

> Where is that F5X Pre?

On my table, waiting to be built.

> Many 2SJ74 will never match because they have to low Idss.

Get some 2SK170GRs.


Patrick

[NicMac]

Originally Posted by EUVL

Get some 2SK170GRs.

I didn't think about that. You never run out of solutions do you

[Nikon1975]

Should I ?

:-)

D.

[EUVL]

These are all old problems known years ago, so are the solutions.
Nothing exciting.




Patrick

[NicMac]

Right place - right time
Go ahead.
Nic

[NicMac]

Originally Posted by EUVL

Nothing exciting.

Not excited. Just learning from others experience.

[Nikon1975]

Originally Posted by NicMac

Of course your 5R1 value was chosen for a reason like most things you do


Of course there is the downside that each 2SJ74 will need a different Rdeg. But as a DIY'er I can live with this minor logistic complication.

Practically it's not a big deal, we just have to stock few resistors of these values, costs around 2 euros.

D.