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Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
References: <3D760B64.CC303206@scs.uiuc.edu> <3D763949.4B6D795E@scs.uiuc.edu> <email@example.com> <firstname.lastname@example.org> <3D808AAC.B0C1DDA3@cern.ch> <email@example.com> <3D858448.DAA17B4A@cern.ch>
Subject: Re: High impedance low noise
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Mon, 16 Sep 2002 09:25:12 +0100
NNTP-Posting-Date: Mon, 16 Sep 2002 09:25:14 BST
"Jeroen Belleman" wrote in message
> James Meyer wrote:
> > On Thu, 12 Sep 2002 14:38:04 +0200, Jeroen Belleman
> > wrote:
> > >The U430 is 6nV/rtHz, but with 5pF input capacitance. I
> > >haven't seen a data sheet for the 2SK162, but I'd guess
> > >it to be 10 times that, if not worse. Can you still get
> > >them?
> > Get U430 FETs? Yes[...]
> Hmm. I wasn't perfectly clear, but it was the 2SK162 I
> was curious about. Anyway, I found a Canadian, 'Tip Top
> Electronics Supply', who still seems to have it. If only
> I could get my hands on a data sheet...
Here is a PSpice model I made many years ago. This might help a bit.
.MODEL J2SK162_XN NJF(Beta=161.6m Betatce=-500m Rd=1 Rs=4 Lambda=10m
Vto=-380m Vtotc=-2.5m Is=12.66f
+ Isr=127f N=1 Nr=2 Xti=3 Alpha=10u Vk=100 Cgd=4n M=1.963
+ Pb=1 Fc=500m Cgs=19.41p Kf=2.5e-003f Af=1)
I made it from the data sheet, but it was so long ago I don't recall how
well I made it.
For referance, here are two spice models for other low noise biploars
.MODEL Q2SC1844_XN NPN(Is=95f Xti=3 Eg=1.11 Vaf=40.7 Bf=449.6 Ne=1.546
+ Xtb=1.5 Br=9.929 Nc=2 Isc=0 Ikr=0 Rc=350m Cjc=11p Mjc=392.1m
+ Vjc=750m Fc=500m Cje=26p Mje=640.7m Vje=750m Tr=31n Tf=233p Itf=200m
+ Vtf=20 Xtf=5 Rb=18.5 Re=400m Kf=1)
.MODEL Q2SA991_XN PNP(Is=4f Xti=3 Eg=1.11 Vaf=11 Bf=233 Ne=1.445 Ise=4f
+ Xtb=1.5 Br=10.43 Nc=2 Isc=40p Ikr=0 Rc=1.2 Cjc=13p Mjc=319.7m
+ Vjc=750m Fc=500m Cje=33p Mje=582.7m Vje=750m Tr=35n Tf=384p Itf=400m
+ Vtf=40 Xtf=10 Rb=12 Re=400m Kf=1)
The 2SC1844 is about 0.65nV and the 2SA991 is about 0.5nv.
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
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