This paper presents fundamentals of SiGe HBT RF linearity and its compact modeling using Mextram 504.12 and the latest Mextram, 505.00, for both common-emitter and common-base configurations.Collector-base junction depletion capacitance model is shown to be significant for accurate modeling of peak IP3 behavior, for which two new options are introduced in Mextram 505.00.Current dependence of avalanche factor is shown to be important for accurate modeling of IP3 peak. This is increasingly important in emerging RF applications requiring SiGe HBTs to operate at increasingly high VCB
with negative IB
.
During the operation of the substation, the main reason for the heating of the switchgear is the eddy current loss. In the daily operation and maintenance of the substation and loss statistics, for some switchgears in the area of direct conductive equipment, there is an abnormal local overheating phenomenon. The main reason for this phenomenon is the eddy current loss in the substation, which seriously affects the safe operation of substation equipment due to the heating defect. This paper analyzes the local overheating problem in substation switchgear and proposes the distribution of eddy current loss and its influencing factors of optimization strategy from the aspect of loss source design. Based on the Maxwell equation, the loss calculation model is established. The optimization method of eddy current loss is comprehensively evaluated according to the distribution characteristics of eddy current loss. The temperature of the bushing surface under different voltage levels is measured, and the error between the calculated results and the measured results is within 2%. Therefore, within the allowable error range, the simulation results and the formula calculation results can fit the measured values well, which verifies the correctness of the established wall bushing heating simulation model and temperature calculation formula. The optimal solution is made to provide a reliable basis for the actual engineering construction. The electric field energy of the bushing is relatively evenly distributed under the actual operating conditions, and the insulating materials are fully utilized to ensure the reliability under high ambient temperature and high current operating conditions.
This paper presents detailed mechanisms of how improved intrinsic collector-base junction depletion capacitance (Ctc
) model in Mextram 505 improves OIP3 peak modeling in common-emitter SiGe HBTs. Harmonics of individual branch currents are examined using custom Verilog-A codes. Interestingly, the third order Ctc
charging current is found to be much lower than the third order main current (IN
), which dominatesthe third order collector current. Early effect is further excluded as the reason for improved third order current modeling. Circuit level propagation of nonlinear Ctc
current towards IN
is concluded to be the main mechanism by which IP3 peak behavior is improved in Mextram 505.
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