Re: Multi-collector/emitter BJTs

From: vishwa (vishwa_23_at_yahoo.com)
Date: 06/05/04 

Date: 5 Jun 2004 14:16:38 -0700

Hi,
 er..there is still some doubt in my mind..for multi-emitter
transistors, do i just 'join' the collectors and bases of two BJTs? on
similar lines, would it work if I just 'joined' the emitters and bases
of the two BJTs?
 i have never done this before, and hence these doubts...also, what
would be a good check to see if the model saturates..by measuring Vce?

thanks!
vishwa

"Kevin Aylward" <kevin.aylwardEXTRACT@anasoft.co.uk> wrote in message news:<qc6wc.10986$wd7.8599@front-1.news.blueyonder.co.uk>...
> Jim Thompson wrote:
> > On 4 Jun 2004 10:39:44 -0700, vishwa_23@yahoo.com (vishwa) wrote:
> >
> >> Hi,
> >> Is there a commerical BJT part for modeling multi-collector and/or
> >> multi-emitter BJTs in spice? Or could I model them just by using two
> >> individual BJTs?
> >>
> >> thanks!
> >> vishwa
> >
> > For multi-emitter situations there is no issue and a
> > multiple-transistor model will work just fine.
> >
> > For multi-collector devices some caution is required if saturation of
> > one collector occurs... you need to add interaction to the model using
> > a subcircuit format.
>
> Or realise that if one saturates, your circuit, in all likelihood, aint
> going to work, so don't do it. If you don't do it, you don't need a
> better model.
>
> Kevin Aylward
> salesEXTRACT@anasoft.co.uk
> http://www.anasoft.co.uk
> SuperSpice, a very affordable Mixed-Mode
> Windows Simulator with Schematic Capture,
> Waveform Display, FFT's and Filter Design.

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