Breakdown voltages affects in BJT/HBT - RF Cafe Forums

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Post subject: Breakdown voltages affects in BJT/HBT Posted: Wed Feb 08, 2006 8:20 pm
Hello people:

I am a student and I need to clarify a point. This questino relates to integrated cirucit transistor and not discrete transistors.

I am using HBT (basically BJT structure) and I was doing DC sweep. When I had just one HBT device and I ran the sweep from IBB=10u to 80uA with VCE=0 to 2.5 it works fine.

But when I have two same devices in parallel and I did DC sweep for the same ranges I get the warning that the base-emitter and base-collector are in reverse bias breakdown.

This seems counter intiutative (may be just because of my lack of knowledge). I thought that now that I have two devices in parallel, the overall transistor should be able to handle more current or at least the same amount of current as the single device and should have the same voltage limiations as the single device because the two devices are in parallel. Why do you think the device is breakdown? Doesn't parallel mean that the collector and base of the two devices are connected together? Thank you.

Marc

Posted 11/12/2012