Subject: Re: Determining bjt noise parameters for Spice models?
Date: Sat, 14 Dec 2002 10:43:52 +0100
Organization: Wanadoo, l'internet avec France Telecom
References: <3DF6537E.B0FC9DBE@worldonline.fr> <3DF90203.C9691374@worldonline.fr> <3DF98E5B.D86102A5@worldonline.fr> <3DFA392F.7FEE50B6@worldonline.fr> <3DFA632B.BA056C3B@worldonline.fr>
NNTP-Posting-Date: 14 Dec 2002 09:43:53 GMT
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> I am yet far from mastering the Spice bjt model, but I suspect that the RB
> parameter is not exactly rbb'....
> But I've adjusted RB, then KF and checked for several Ic, Ri - the updated
> model 2SC3329 showed a behaviour ressemling that in the datasheet! I needed
> to set RB=24, KF=0.38e-16 (AF=1).
> I've then done the same thing for 2SC1775 ; obtained RB=200, KF=1e-17.
> But the third stock model, for 2SA876, behaved differently: even without RB
> in the model, it exhibited the thermal noise slightly exceeding the
> datasheet specs... In order to set up the flicker noise I had to add some
> RB=6, and large KF=1e-10.
Well, I've then simulated my circuit (a voltage follower) and have obtained
huge noise figures (about 0.2 uV/sqHz @ 5kHz)! Something looks wrong with the
model. I have then set RB and KF for 2SA876 the same as for 2SC1775 (its
complementary), and the circuit noise figure became reasonable... But
I believe that the model could still be improved.
> > Kevin Aylward