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SPICE

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bruce
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Username: bruce

Post Number: 429
Registered: 04-2008

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Posted on Wednesday, 01 September, 2010 - 10:50 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi,
I was trying to do a simulation of a fairly simple circuit for which I chose an npn transistor type ZTX689B ( there was one just lying around ). There was no Spice model on LTSpice, so I Googled ( they cant touch you for it ). The Zetex website is called Diodes as I understand it, and there is no model for this part. Terrific. The business of actually writing your own model looks dreadfully complicated. I'm a touch out of my depth here; can anyone give me a bit of assistance?

Bruce
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microguy
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Username: microguy

Post Number: 198
Registered: 01-2010

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Posted on Wednesday, 01 September, 2010 - 11:07 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Easy. Choose another part!
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bruce
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Username: bruce

Post Number: 430
Registered: 04-2008

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Posted on Wednesday, 01 September, 2010 - 12:12 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Golly, I would never have thought of that. So glad we have you on the team.

I did a simulation with a 2N2222. Jolly clever this Spice thingy. The transistor survived because I had overestimated Ipk; it's only 300mA.
Still, the Vce(sat) of these Zetex transistors is much lower, isnt it? so it might be worth shoving one in.
As the actress said to the Bishop.
Bruce
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microguy
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Username: microguy

Post Number: 203
Registered: 01-2010

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Posted on Wednesday, 01 September, 2010 - 02:05 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

How hard would it be to edit a current part? Copy one Zetex does have, and just edit the parameters to match the one you have?

Can't say about the the Vsat question, haven't looked at them.
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gajjer
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Username: gajjer

Post Number: 335
Registered: 05-2007

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Posted on Wednesday, 01 September, 2010 - 05:45 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi bruce
I found this in my Simetrix models library.
*
*ZETEX ZTX689B Spice Model v1.0 Last Revised 12/10/04
*
.MODEL ZTX689B NPN IS =1.8E-12 NF =0.994 BF =1500 IKF=3.2 VAF=24
+ISE=.218E-12 NE =1.345 NR =0.996 BR =310 IKR=.8 VAR=4 ISC=0.36E-12
+NC =1.26 RB =.2 RE =.035 RC =.036 CJC=74E-12 MJC=.35 VJC=.485
+CJE=248E-12 TF =0.72E-9 TR =4.9E-9 XTB=1.13 TRE1=4E-3 ITF=5e-3
*

You should be able to paste it into an existing library. But then I don't use the pspice that you do.

You will find that getting models is a pain in the r's. They are not easy to develop yourself, you won't find the parameters in the datasheet. You might also find that the models don't always reflect the operation of the component. I have found this with some op amps which commonly use behavioural modelling rather than actual transistor parameters that they are fabricated from.
Also note that the model will be for typical values. When designing ICs I could get high and low value models too but have not seen that for discrete components.

Oh yes. And your wife said will you stop leaving transistors lying around!

BTW I have a parcel for you if you can privately mail me your address.
cheers
gaj
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ant
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Username: ant

Post Number: 693
Registered: 05-2006

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Posted on Wednesday, 15 September, 2010 - 09:16 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hello Bruce,

Might part of your problem lie in the fact of the Zetex site being called "Diodes"?

Regards Ant
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741
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Username: 741

Post Number: 194
Registered: 08-2005


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Posted on Tuesday, 21 September, 2010 - 04:26 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Ant: Diodes Inc gobbled up Zetex about 18 months back.

Thus, we now have zero indiginous semiconductor manufacturers in the UK. In fact if anything complicated needs making (like a nuclear power station) we have to ask the froggies

Don't get me started..
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microguy
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Username: microguy

Post Number: 226
Registered: 01-2010

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Posted on Tuesday, 21 September, 2010 - 10:48 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Ah, you can ask Russia for help on the nukes, they're helping everybody these days!

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