single transistor amplifier
I would try a single N channel VFET, made by Sony, Yamaha, or even a mil supplier, where they are called static induction transistors. This is a natural, high current triode with an 8 ohm loading capability. Unlike a follower, it will have some voltage gain and be somewhat more free from power supply loading. For the record, you will need less inductance as you increase the bias current, so a 1-2 amp idle current would need 1/10 as much inductance as 100ma idle current.
I would try a single N channel VFET, made by Sony, Yamaha, or even a mil supplier, where they are called static induction transistors. This is a natural, high current triode with an 8 ohm loading capability. Unlike a follower, it will have some voltage gain and be somewhat more free from power supply loading. For the record, you will need less inductance as you increase the bias current, so a 1-2 amp idle current would need 1/10 as much inductance as 100ma idle current.
Variac said:So that would be John Curl the amp designer?
Is this site the best or what!!!!
I'm afraid it's my fault.
http://www.audioasylum.com/forums/prophead/messages/5114.html
Oh well. Perhaps John and I can split our head-butting between AA and here and give the folks at AA a bit of a break.
se
I think using an input- transformer will result in a lot of trouble because it transforms also the input impedance of the MOSFET and in in this way the input capacitance seen at the input of the transformer.
A 1:9 input transformer will increase input capacitance to 81-times of the MOSFET (mainly Cgd). A Power-Mosfet with a Cgd of about 200 pF will result in an input capacitance of 16nF highly nonlinear. I think it's difficult to drive this load from peamp...
A 1:9 input transformer will increase input capacitance to 81-times of the MOSFET (mainly Cgd). A Power-Mosfet with a Cgd of about 200 pF will result in an input capacitance of 16nF highly nonlinear. I think it's difficult to drive this load from peamp...
Now we'll have Divergence AND Curl!
I was relieved to see you just posting at AA and giving us a much need rest. I knew it wouldn't last.
I welcome Mr. Curl and hope to enjoy his pithy remarks and expert advice. I
would advise him not to hold back as we are an imformal and outspoken group. In fact I could even say we are the Fight Club of audio forums. Mr. Curl will you weigh in on the inverting amp debate so some unwitting expert with a chip amp on his shoulder can tell you that you are wrong and we can enjoy the consequences?
http://www.diyaudio.com/forums/showthread.php?s=&postid=212299#post212299
Steve Eddy said:
I'm afraid it's my fault.
http://www.audioasylum.com/forums/prophead/messages/5114.html
Oh well. Perhaps John and I can split our head-butting between AA and here and give the folks at AA a bit of a break.
se
I was relieved to see you just posting at AA and giving us a much need rest. I knew it wouldn't last.
I welcome Mr. Curl and hope to enjoy his pithy remarks and expert advice. I
would advise him not to hold back as we are an imformal and outspoken group. In fact I could even say we are the Fight Club of audio forums. Mr. Curl will you weigh in on the inverting amp debate so some unwitting expert with a chip amp on his shoulder can tell you that you are wrong and we can enjoy the consequences?
http://www.diyaudio.com/forums/showthread.php?s=&postid=212299#post212299
bocka said:
You're looking at it backwards. A 1:9 step-up transformer doesn't reflect the load back to the source by a factor of 81, but a factor of 1/81 (looking back from the load to the source it's a step-down transformer). It's the source that gets reflected to the load by a factor of 81.
se
Ok, fine diskussion, what if i don´t want to use any transformer, and only build a simple class a, inductive loaded, one FET as gain device. Whats the mysterie about setting the bias? Fred, could you say me a solution how to connect the "?" signed pins? Do i need something like small resistor in the + inductor Fet Gnd pass to feel the current and make me a voltage, and a transistor for controll the gate related to this voltage?
Attachments
The Vfets that look promising are the 2SK60 and the 2SK70. These will most probably be rare and expensive, but they would be an interesting device for a simple amplifier. Also, I was confused of the position of the inductor. I have never used an inductor as a load, and of course, it should be very high in inductance if possible. I was thinking about the use of inductors in a choke input power supply.
john curl said:
Are they? Can't find any useful information about them anywhere on the net. Saw a header in a Google search regarding enhancement mode but the page wouldn't display. I'm thinking perhaps the mention of enhancement mode was relating to something else.
"AMS - 2SK60 « MOSFETs; N-Ch; Enhancement « MOSFETs and TempFETs"
se
You got my interest piqued. I see a complemetary pair in the 2SK70/2SJ20 manufactured by NEC but can't find any info on the net other than 100V 6A 5W 600S. I'm drooling. I can't read the Japaneese chicken scratches but maybe one of our Oriental buddies can. They may be depletion mode devices.
Babelfish will translate Spanish but the others are untranslatable so far. When we have an effective translator for all languages the world will shrink by magnitudes. Here is a link to a Sony 2SK60 curve surrounded by stuff I might be able to read after one more.
http://www.sm.rim.or.jp/~konton/V-FET.html
http://www.sm.rim.or.jp/~konton/V-FET.html
>There is no question about it. The 2SK60 is a depletion mode device. I checked it realtime on a TEK 577 curve tracer.
OK! I need to find a source. Are these new or old devices?
>Bah! They should just learn how to speak English like everyone else!
When in Rome....
I have listened to my Vietnamese girlfriend for 3 years now and doubt if I could pick up the fluency of a three year old in my lifetime. Spanish, German, French, Italian, Portugese, I could learn in months.
OK! I need to find a source. Are these new or old devices?
>Bah! They should just learn how to speak English like everyone else!
When in Rome....
I have listened to my Vietnamese girlfriend for 3 years now and doubt if I could pick up the fluency of a three year old in my lifetime. Spanish, German, French, Italian, Portugese, I could learn in months.
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