Multi-collector/emitter BJTs

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.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
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I love to cook with wine.      Sometimes I even put it in the food.

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 snipped-for-privacy@anasoft.co.uk

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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

If you are going to physically combine de=iscretes, then i suggest you match the Vbe (all measured at desired operating current) within a few millivolts; a mismatch of about 2.5mV will create an Ie ratio of 1.10 .