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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> Spice model explanation needed!! ^^ https://designers-guide.org/forum/YaBB.pl?num=1144419451 Message started by ee484 on Apr 7th, 2006, 7:17am |
Title: Spice model explanation needed!! ^^ Post by ee484 on Apr 7th, 2006, 7:17am Hi, all, I have questions about Cdb and Cjd. If my understanding is correct, in saturation, Cjd is roughly Cdb. (Cjd = drain-bulk junction capacitance (drain bottom plate and sidewall capacitance, Cdb = dQd/dVb - transconductance) In spectre op values, Cjd and Cdb are different in saturation region. Do you guys know why? (Cjd is several order bigger than Cdb) I believe that Cdb in op values in spectre is in F, not F/m^2..or so. Since Cdb is defined as dQd/dVb, it is small signal capacitance. What about Cjd? Is it small signal capacitance too? (I named small-signal capacitance, do you have better name and explanation? - Is it capacitance load at the drain while it is being biased?) If I want to account drain load capacitance of a transistor, do I have to consider Cdb or Cjd? (Bottom line: How does Cdb we see in analog books differ from Cdb in spice?) Thanks in advance!! PS: Any references are welcome!! (Easy to read ones..^^) |
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