Well, I guess the cat's out of the bag.
First Watt is in production with a JFET power amplifier, with
delivery next month, using the Lovoltech vertical power JFETs.
The DIY version of it can be found on
www.passlabs.com/np
under the title ZV8_POWER_JFET.PDF
This is the final draft, but you have an opportunity to correct
my grammar and errors of fact.
Enjoy.
First Watt is in production with a JFET power amplifier, with
delivery next month, using the Lovoltech vertical power JFETs.
The DIY version of it can be found on
www.passlabs.com/np
under the title ZV8_POWER_JFET.PDF
This is the final draft, but you have an opportunity to correct
my grammar and errors of fact.
Enjoy.
Nelson Pass said:
Ah, that's what I thought.
I'd looked at those some time back but their input capacitance was way too high for how I'd originally thought of using them (their already high input capacitance would have been magnified by a factor of 100). And oddly enough, I was looking at them again just the night before I saw Srajan's blurb on 6 Moons.
In any case, coolness!
se
Nelson Pass said:
Good question. In fact there is some load line action in the amp
by virtue of the limited transconductance of Q2, and we can
easily modulate it further. I was saving that particular adjustment
for another time, not wanting to give you a headache right
away.
Right! Makes a lot of sense. Both
. So we can look forward to a version with some amount of pos feedback? (Watch all those cats Nelson!).BTW, Clever circuit. The art of leaving out.
Jan Didden
Mr. Harrington gave me a smaller copy of the ZV8 for those
of you with dial-up service, and to save Choky the trouble.
It;s at www.passlabs.com/np with almost the same name.
of you with dial-up service, and to save Choky the trouble.
It;s at www.passlabs.com/np with almost the same name.
janneman said:
Thank you. I know you don't dispense praise lightly.
As to the positive feedback, the modulation is similar to "muting"
the cascode. Some small variation is allowed through, but it
works to slightly decrease the voltage across the JFET on the
negative output swing and increase it on the positive, running
counter to the natural tendency of the transconductance to
increase at higher current and decrease at lower. This gives
some cancellation of the two forms of nonlinearity, which is what
I was referring to when I mentioned working the triode load-line.
Nelson Pass said:
Thank you. I know you don't dispense praise lightly.
As to the positive feedback, the modulation is similar to "muting"
the cascode. Some small variation is allowed through, but it
works to slightly decrease the voltage across the JFET on the
negative output swing and increase it on the positive, running
counter to the natural tendency of the transconductance to
increase at higher current and decrease at lower. This gives
some cancellation of the two forms of nonlinearity, which is what
I was referring to when I mentioned working the triode load-line.
You're welcome.
Coincidentally, that was also what I was referring to when I mentioned "some amount of pos feedback".
Jan Didden
Nelson Pass said:Mr. Harrington gave me a smaller copy of the ZV8 for those
of you with dial-up service, and to save Choky the trouble.
It;s at www.passlabs.com/np with almost the same name.
sorry ,Master-I can't see smaller file at ********/np .
in any case -420KB version of ZV8 is at
http://czsr_bac.on.neobee.net/ZV8.pdf
cheers to all!
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