I have the following SPICE parameters for an NPN
IS=8.11E-14 BF=205 VAF=113 IKF=0.5 ISE=1.06E-11
+ NE=2 BR=4 VAR=24 IKR=0.225 RB=1.37 RE=0.343 RC=0.137 CJE=2.95E-11
+ TF=3.97E-10 CJC=1.52E-11 TR=8.5E-8 XTB=1.5
I am stuck on how to find Cpi ( from hybrid pi model) from the SPICE parameters.
Is the below assumption correct?
Cu = CJC
Cpi = 2*CJE + gm * TF
where gm is IC/VT under standard conditions
Best Answer
In 'The Spice Book' from Vladimirescu it is
Cu = TR * gmR + CJC
Cpi = TF * gmF + CJE