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Model for JFET

Question asked by dlesa on Apr 4, 2003
Latest reply on Apr 9, 2003 by dlesa

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Hi,

I am new to GENESYS and I need to design an oscillator. I would like to use the J310 N channel JFET but I can't find the model in the libraries that I have. How do I find this model? I have looked on the web page of the supplier (Fairchild Semi) but can't seem to find it. I was led to believe this is a common JFET to use for RF apps.

Thanks,
Donovan

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SAABERICSSON Apr 7, 2003 1:38 AM
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J310 is manufactured by Vishay (http://www.vishay.com/fets-small-signal/SSFsgnchjampP). SPICE parameters are here:

http://www.vishay.com/docs/70597/70597.pdf

"
Hi,

I am new to GENESYS and I need to design an oscillator. I would like to use the J310 N channel JFET but I can't find the model in the libraries that I have. How do I find this model? I have looked on the web page of the supplier (Fairchild Semi) but can't seem to find it. I was led to believe this is a common JFET to use for RF apps.

Thanks,
Donovan
"
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dlesa Apr 9, 2003 8:43 PM
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Hi,

Thanks for the spice model for the device. I tried to use this model and received virtually the same result (I was using the U310 model before).

I don't have the non-linear part of GENESYS (harbec) so I rely on the open loop gain method of design. What is concerning me is that the circuit oscillates reliably (I have tested with a protototype), but the simulated open loop gain at the desired frequency is -23dB. This would prevent the oscillator from ever starting up! The shape of the s21 response is about what I would expect though.

Obviously something in my simulation is not correct. In case it helps: the oscillator is an LC colpitts type for operation at 25MHz.

Does anyone have any ideas?

Thanks.
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Model for JFET

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