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Old 12th January 2009, 01:14 AM   #1121
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Default JFET Model

OK here is the JFET model from Linear Systems.
If anyone can find an error with it let me know.
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Old 12th January 2009, 01:25 AM   #1122
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Hi Homemodder
20kHz looks vey bad indeed. OK there is definitely something wrong
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Old 12th January 2009, 11:18 AM   #1123
cHoc is offline cHoc  Netherlands
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For the B1 could you also use a modified version of the Pearl psu to power it? For as far as i can understand the psu you have to modify/change the resistors around the 2 ZTX450 and the IRF9610, and not only lower the input voltage, but what should the values become to get 18v out of the psu, could anyone help me with that??
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Old 12th January 2009, 11:56 AM   #1124
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Quote:
Originally posted by cHoc

... what should the values become to get 18v out of the psu ... ??


First off, I recommend D1 of 9.1V Zener, and R12 is to be lowered to 10K from 22K. Then it will give us 18V output.


Cheers,

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Old 12th January 2009, 12:32 PM   #1125
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by cHoc
For the B1 could you also use a modified version of the Pearl psu to power it? For as far as i can understand the psu you have to modify/change the resistors around the 2 ZTX450 and the IRF9610, and not only lower the input voltage, but what should the values become to get 18v out of the psu, could anyone help me with that??

Quote:
Originally posted by Babowana



First off, I recommend D1 of 9.1V Zener, and R12 is to be lowered to 10K from 22K. Then it will give us 18V output.


Cheers,

>><<



from where is current for D4 comming ?
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Old 12th January 2009, 12:44 PM   #1126
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Quote:
Originally posted by Zen Mod



from where is current for D4 comming ?


From the rail and through an "additional resistor" (it is missing now) to the zener. The size of resistor is to be considered based on the zener current.

Why don't you just add the resistor and correct us at the first place?
Naughty boy . . .


Cheers,

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Old 12th January 2009, 12:48 PM   #1127
cHoc is offline cHoc  Netherlands
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Quote:
Originally posted by Zen Mod



from where is current for D4 comming ?
You're right, Zen mod, i forgot one resistor, it is in this scematic added, and the value of R12 is changed to 10k
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Old 12th January 2009, 01:05 PM   #1128
AndrewT is offline AndrewT  Scotland
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Hi,
What is the gate to source voltage on the FET?
What are the Currents through R8 & R9?
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Old 12th January 2009, 04:02 PM   #1129
JimT is offline JimT  Canada
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thanh1973,

Here is the B1 model I did for LTSpice. It's is simplified a bit from your's, but you should be able to use this to compare differences. Like you I have set the 25k input pot set to half. Simulating the transient, I get the 2nd harmonic at -85dB, 3rd at -120dB and 4th at -150dB and no higher harmonics. The AC Analysis shows that the bandwidth goes up to an F3 of about 3 MHz.

Hopefully you can work out your problem from this.

Jim
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Old 12th January 2009, 08:38 PM   #1130
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Thanks you fixed the problem.
I went through each directive starting with the one on top in your circuit, and added an extra directive after each run. It wasn't until .plotwinsize=0 was added that it worked.
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