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Old 12th March 2008, 09:41 AM   #1
rubydac is offline rubydac  Hong Kong
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Default discrete jfet input opamp

From 2sk389 jfet input used output from drain pins of them instead output of ne5534 by cascode to pin1/8 and short input pin 2/3 of ne5534 to ground !!!

So now you have jfet input opamp instantly !!!

I took it from studio amplifier (**,*** USD)
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Old 12th March 2008, 10:06 AM   #2
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This is a classic solution from the stone age. You can find it in application notes from National from the 80's. Nothing you will do today since the opamps got much better.
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Old 12th March 2008, 10:14 AM   #3
rubydac is offline rubydac  Hong Kong
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Lightbulb Give me some link

Please Mr.perander send me some link which used this schematic.
I find all of same as this method but I never seen about this ?!?

Thanks
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Old 12th March 2008, 01:12 PM   #4
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You have a wonderful description of this paleolithic circuit in Walt Jung's "op amp applications" -- should be on everyone's bookshelf.
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Old 12th March 2008, 01:25 PM   #5
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Default Re: Give me some link

Quote:
Originally posted by rubydac
Please Mr.perander send me some link which used this schematic.
I find all of same as this method but I never seen about this ?!?

Thanks

http://www.national.com/an/AN/AN-222.pdf

There is also an app note in an old Siliconix application book but it's hardly to befound on the net. I have this app note somewhere. The idea is the same as the link above but JFET's were used and the opamp was NE5534.

http://www.analog.com/library/analog..._handbook.html
http://focus.ti.com/lit/an/slod006b/slod006b.pdf
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Old 12th March 2008, 04:59 PM   #6
rubydac is offline rubydac  Hong Kong
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Smile super thanks

Thanks a lot Mr.Peranders
Could you suggest me to use this schematic in tube amplifier ?

Thanks
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