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Old 2nd February 2006, 07:01 AM   #1
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Smile Krazy JFET-cascoded Pass SOBOZ



Hi

I am trying to build this.
My most concern is how to set up the gain of about 14-20dB.

Appreciate any comment, advice, or criticism . . . plz . . .

Regards
jh
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Old 2nd February 2006, 09:44 AM   #2
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Hi,

gain is set through the drain resistors and the chosen fets.

gm = 2xIdss/Vp

Gain = gm x Rdrain

I donŽt have any data on the J310 so youŽll have to calculate it for yourself.

What is the resistor between output and input?

William
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Old 2nd February 2006, 11:31 AM   #3
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Thanks, William

Well noted.
Attached is a brief data about J310 I prepared.
I am thinking the Rd of 1K.

The minimum Gfs of J310 is 0.008mhos.
Min. voltage gain A = Gfs x Rd = 0.008 x 1000 = 8 (18dB)
The maximum Gfs is 0.018mhos.
Max. A = 0.018 x 1000 = 18 (25dB)

Hmmm . . . the gain would be between 18-25dB.

The resistor betweem the output and the input is my "uncertainty." I was unsure about the voltage gain of this concept so that I put my "uncertainty" there in case I need a negative feedback. I will remove it and repost the circuit.

Any other comments . . . ?

Regards
jh
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Old 2nd February 2006, 11:38 AM   #4
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Attached is Rev.1

Help me with your comments . . . plz . . .

Regards
jh
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Old 3rd February 2006, 01:44 AM   #5
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I read data sheet again.
And, re-estimated the voltage gain.

Min. A = 0.011 x 1000 = 11 (20dB)
Max. A = 0.013 x 1000 = 13 (22dB)

Hmm . . . 20-22dB . . .

I wonder if this way of estimation is correct.
So far, nobody seems intersted in or has no time . . .

Regards
jh
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Old 3rd February 2006, 01:55 AM   #6
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I dunno....
now I'm breakin' and bangin' my head with Aleph J
besides-I'm greenhorn....
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Old 3rd February 2006, 02:13 AM   #7
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I see . . .
Following this project, I go with JFET-cascoded F1 . . .



Regards
jh

Where is my power JFET . . .
Where are they . . .
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Old 3rd February 2006, 06:16 AM   #8
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Quote:
Originally posted by jh6you
I see . . .
Following this project, I go with JFET-cascoded F1 . . .

Could you please hurry up

I was thinking about the same thing, but due my limited understanding of the world and more specificly mofsets/jfets I need a complete ciruit.
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Old 3rd February 2006, 07:53 AM   #9
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Hurry up . . . ?
The music from F1 is already !!!
I do not have the power JFET . . .
Mmm . . . I could create a new thread with a conceptual darwing . . . if the master does not mind . . .

I donnu MOSFET/JFET either, but we are lucky with good supports here . . .

Back to the subject, I am going to try the shown Krazy, 10 days later when I return back to the exciting hell from the boring heaven I am staying now. Still have time for your positive or negative feedbacks.

Regards
jh
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Old 3rd February 2006, 08:36 AM   #10
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Ok ok, I will build the F1.

I am still waiting for my heatsinks for it, but I should get them soon. All the other parts are already waiting for me on my work table.

I'm sure it will be much better than my gainclones, but I also know that I will have to change it to JFet F1 (or what ever it is goning to be called) when I can.

If one only had the time to learn, but I have so many other projects and a full time job to care of.

Good luck with the Krazy.
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