12/13/2023 0 Comments Macspice plot current![]() There were indeed some symmetrical bipolar transistors on the market these days, for example, the AC130 from Valvo and in this case, BR=BF would indeed be the right choice. Incidentally, the above changes to the AC128 model didn't affect the other AC128 characteristics significantly, so this might even be a useful general-purpose strategy. Note, however, that the third root of x might only be valid under the given circumstances, because the corresponding Spice-internal equations also contain XTB and 1/NC as exponents in this same context. The other models will probably require slightly smaller values, but I haven't verified this explicitly. Here, x=6 turned out to be a good choice. Some manual trials revealed that the following parameter changes would be appropriate for my AC128 model: Without going into details of the corresponding Spice-internal equations, a reasonable first-order heuristic might be to change only the leakage-current-related parameters ISC (and probably ISE accordingly) and XTI so that the red curve in my third plot is shifted upwards by the above amount. ![]() Ube' characteristics-and this would inevitably violate my entire optimization! For other models, a slightly different factor might apply.Ĭhanging IS accordingly, however, is not a particularly good idea as this parameter affects not only the leakage currents of both junctions, but also the 'Ie vs. The specified maximum is about 2.5 times the average leakage current for all temperatures. For the AC128, the maximum values of the collector-base leakage current can indeed be found in the Valvo datasheet minimum values are not specified, though. I've made a few heuristical studies in this direction. In a 9V world there may be little need to specify a reverse Early voltage but that's not hard. I think if it matters to your designs you need to measure the devices you can get and work them into *your* copy of the model. And as the processes improved a given device may have different actual parameters in different eras. Such techniques give no or some control of the two junctions.Īnd since the "reverse" properties were rarely interesting, they were not specified (don't promise more than the customer demands). Another is to put two P pills on a slice of N and bake the whole thing until it almost diffuses-through. Then saw between alternate N stripes so you get P-N-P slices. One is to pull a crystal from the melt while alternating N and P dopants so you get a zebra-stripe sausage. Not that it is is material related, but "all" Silicon will have refined junction processing, heavier on Collector.īack in the beginning there were several crude ways to make transistors, and some of them made Collectors and Emitters the same.
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