http://www.infineon.com/dgdl/irfps3810pbf.pdf?fileId=5546d462533600a40153562ce01f2035
It has the same kind of Triode transfer-curves as the SIT Nelson Pass presents in his Introduction to Static Induction Transistors article:http://www.firstwatt.com/pdf/art_sit_intro.pdf
With a low 0.5 C/W total thermal resistance, 100 volt drain to source rating and 580 watt power rating, it should be very suitable for a nice sounding single ended amp.
Cheers,
Johannes
It has the same kind of Triode transfer-curves as the SIT Nelson Pass presents in his Introduction to Static Induction Transistors article:http://www.firstwatt.com/pdf/art_sit_intro.pdf
With a low 0.5 C/W total thermal resistance, 100 volt drain to source rating and 580 watt power rating, it should be very suitable for a nice sounding single ended amp.
Cheers,
Johannes
I guess simplicity and single ended designs is the key with these devices. A common source with some source-degeneration, 0,22 to 0,5 ohm or so, and a simple power-resistor drain-load should sound marvelous.
Mostly trial and error. The "38" in the name IRFPS3810 caught my attention. I like the IRL3803V and the IRLB3813, and I hoped there was some similarities between them.
The main attribute with a SIT or a "triody" device is not that it is a depletion mode device. It is the ohmic behavior, where the current increases with an increase in voltage drain to source without an increase in voltage between gate and source. It is the exponentially rising gain with an increase of voltage over the device.
The IRFP7430 and IRL3803V is not as linear as this IRFPS3810. Their transfer-curves deviates from the ohmic behavior in a non-linear fashion.
Even though I really like the IRFP7430 I believe the IRFPS3810 is a much nicer device in many ways. Less gate-capacitance, much more linear transfer-curves, a much larger Safe operating Area and a much better voltage-rating.
I have been playing a lot with different methods of achieving a Triode charterer by the use of Schade feedback, but it all comes down to the simple fact that even Schade feedback is a kind of global negative feedback. I generally prefer an inherent Triode charcter without the use of global negative feedback. The negative feedback makes everything sound correct and dull like an accountant, even though Schade feedback does this much less then normal global NFB. It sucks the life out of the reproduction of music.
An IRFP7430 breaths life into the reproduction of music (with some aggressive brutality). I hope the IRFPS3810 does so with less distortion then the IRFP7430.
The published transfer-curves indicates this.
Cheers,
Johannes
It's local feedback no global.
Made with two resistors but not the only egsisting trick....
Iteresting article how transform ordinary jfet to be triode like :
The Trioderizer - a solid state triode
The same technique is used in tube amplification for pentodes.
Cheers
Made with two resistors but not the only egsisting trick....
Iteresting article how transform ordinary jfet to be triode like :
The Trioderizer - a solid state triode
The same technique is used in tube amplification for pentodes.
Cheers
Attachments
Johannes, i know you've been looking at these for quite some time so permit me an innocent question - the curves suggest that this region only exists at very low VDS - I can't quite get my head round how you get any power out of the device if there's only 1-2 volts across it ?
A feedback taken from the amplifier output node and injected back into its input node is per definition a global feedback.
I prefer this method of achieving Schade-feedback. The Bastode is a very linear, stable and fast circuit. Even with the Bastode circuit the Schade feedback sounds more dull then without the Schade feedback. See below for a "Triody" no-global-feedback version of the Bastode circuit.
The no global feedback version sounds much more open, vivid and alive then the Schade feedback version.
Cheers,
Johannes
" A very ugly looking Pentod-ish Mosfet "
Do you mean Schade feedback = Global feedback ?
I don't see amplifier must have his output connected to audio input because your jfet or mosfet are "schaded".
I am first to like amp's without any feedback but electronic design it's art of compromisse's.
If you can get much better frequency response linearity and less distorstion is just fine.
For example read about Mr. Pass Sony Diy Vfet amp circuit.
Best regards
This trioderizer trick was used in reparation of antique radio's and remplaced scarce to get triodes from 1920.
I don't hear or use. It's interesting possibility in some specyfic cases.
It's noting to compare with massive feedback.
Greetings
No, you are right. If the Schade feedback is applied around a single transistor as a building block of a more complex amplifier then it is not global feedback. I have been building so many single stage amps, that I automatically view the Schade feedback as a global feedback. Source-resistance (local source degeneration) is local feedback. I guess feedback into the top transistor in a Bastode or Cascode blurs the line somewhat.
Schade feedback does not necessarily sound bad. Nelson Pass transformer-coupled Schade feedback sounds very very nice. The Schade feedback Bastode circuit sounds very nice to, but I prefer the very vivid, open and alive character of a no-global-feedback amp. This might in part be due to the increased output impedance.
Cheers,
Johannes
Hi Johannes, thank you for sharing your find, I hope we can some day find a nice triode-like FET, maybe I will try this one as I am keen on trying a choke loaded SE, what do you think would it be a suitable candidate?
PS. BTW while I have your attention, I hope you don't mind me pointing it out and it's not my intention to annoy, but can you please attach your pictures instead of inserting them into the text body.
Any time I click on these picture it makes my browser leaving current web page and so I have to go back and reload, unfortunately I am repeating the mistake over and over as I don't know which pictures zoom in and which doesn't, please be kind read more in below link.
http://www.diyaudio.com/forums/foru...doesnt-get-properly-uploaded-attachments.html
Regards
PS. BTW while I have your attention, I hope you don't mind me pointing it out and it's not my intention to annoy, but can you please attach your pictures instead of inserting them into the text body.
Any time I click on these picture it makes my browser leaving current web page and so I have to go back and reload, unfortunately I am repeating the mistake over and over as I don't know which pictures zoom in and which doesn't, please be kind read more in below link.
http://www.diyaudio.com/forums/foru...doesnt-get-properly-uploaded-attachments.html
Regards
An externally hosted image should be here but it was not working when we last tested it.
Today I finally got a hand full of these...
I have been simulating a lot of different amps with these devices, and I guess I will start with a simple no feedback Zen amp to hear as much of their own character as possible.
The IRFP7430 is much more "triody" but not really a well behaved device. They need some heavy handed guiding to behave well and sound nice. They are always fun, but not always nice sounding.
I hope the IRFPS3810 strikes a better balance between raw energy and smooth musicality.
Cheers,
Johannes
Astute observation, making the part very interesting. The curve portion
circled as the "concave" shape of a Triode or SIT, and it lies within the load-line
region.
But note that both sets of curves are the same except for temperature....
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