Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans

[massimo]

When are you planning to unveil the new parallel Jfet front end?

 

[Zen Mod]

arranging to get little buggers in quantity

though, have no doubt will they function or not

anyway , better to wait an check things

 

[massimo]

and WLF! (always)

 

[Zen Mod]

SEF

this one goes in prototype

 

[ElFishi]

no gatestopper at 9240?

This looks like an M2 @1.9A with the output moved to the source of the p-channel MOSFET.
Can you elaborate on the rationale?

 

[Zen Mod]

probably it will not oscillate , but gate stopper is conditio sine qua non , at least in my head

so , no need to draw it all the time , especially when I forget .....

(so , that was good question!)

rationale for output resistors arrangement is nothing else than THD spectra ( and dynamic behavior of mosfets in output)

it looks best this way

edit: just checked - both gate resistors are included on pcb

 

[lhquam]

Maybe I missed something earlier in the thread, but what would happen if you put the 0R27 sense resistors and the opto input circuit in the drain leg of M1 and eliminated degeneration of the output stage?

 

[Zen Mod]

I think I covered (also commented on) all possible iterations I could think of ....... so , no - Shade amp must have source resistors , to have what I need of transfer characteristics and behavior of outputs (DEFiSIT being ethalon for that)

regarding your question , I believe it's covered with :


Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans

and - last but not least:

Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans

 

[cwtim01]

btw ....... made sanity (sim) check of 2SK180 based DEFiSIT , made with ACS chips

nada - not big enough (voltage) window between gates of 2SK180 and IRFP9xxx to keep current in sane bracket

same case with SJDP

Sorry to quote a relatively old post, but the "1, 2, SIT3" thread triggered me to ask again.

I have some 2SK180D, that gives Id of around 1.5A at Vgs of -3.2V (Vds=20V), would they be feasible devices for the DEFiSIT. (attached are the measurements of the 2SK180D).

 

[Zen Mod]

if you go back in thread , you'll find (simulated) iteration with 2SK180

I can't do more , further development demands having actual part on bench

edit: found exact post : Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans

 

[cwtim01]

Thanks, could you share the .asc file of the circuit at the linked post.

 

[Zen Mod]

sure

in fact , found later iteration ,somewhat better

 

[Nelson Pass]

I have some 2SK180D, that gives Id of around 1.5A at Vgs of -3.2V (Vds=20V), would they be feasible devices for the DEFiSIT. (attached are the measurements of the 2SK180D).

All you need is a P channel Fet with Vgs of 3.2V at same current and temp.

Maybe P Fets in parallel.

There are adjustments that can be made if it's not exact.

 

[Zen Mod]

All you need is .....

Baaad Papa , baaaad!

 

[cwtim01]

Thanks Mr. Pass and ZM . It seems quite possible to find a matching P FET, but I'll need to get familiar with the SPICE circuit first.

I have another question though, if you don't mind. In the "DEF Amp" thread, it describes a way to adjust the Vgs matching through 3 resistors. In the DEFiSIT amp, opto-coupler is used - what is the reason for the change.

 

[Zen Mod]

no opto in DEFiSIT
frankly , dunno for production iteration ......

 

[Nelson Pass]

The LED in series with the zeners was just used to trim the voltage,
me not having the low voltage zeners laying around.

 

[Zen Mod]

yup, that one is opto

 

[First Watt Guy]

Any idea for SJEP120R100 and IRFP9240 in DEFiSIT ?

 

[Zen Mod]

I made sim with SJDP

tonight with SJEP , OK ?