• Analog Custom Design & Analysis Examples

opt_ex17 : Mextram Level 504 Bipolar Model Extraction

Requires: Utmost IV, SmartSpice, SmartView

Minimum Versions: Utmost IV 2.2.0.R, SmartSpice 4.30.0.R, SmartView 2.34.0.R

This example describes how to extract a Mextram Level 504 model for a bipolar transistor. To extract the model, typical forward and reverse operation DC characteristics and reverse bias capacitance characteristics of each junction are required.

The project file opt_ex17.prj and the data file opt_ex17.uds for this example should be loaded into your database. When opened, the project will look as shown in opt_ex17_01.png and when plotted, the example measured data will look as shown in opt_ex17_02.png .

The optimization sequence, which fully automates the extraction of this Mextram bipolar model example, has seven sections. The objective of each section is to isolate a device characteristic and then to optimize only those model parameters which account for this device behavior.

The Mextram bipolar model couples the capacitance and the charge equations together. Therefore, it is important to extract the capacitance parameters first to avoid having to readjust the DC model parameters later.

The first section extracts the CJE , PE , VDE , CJC , PC , VDC , CJS , PS , VDS , and XP model parameters which describe the reverse bias capacitance characteristics of all three transistor junctions.

Once the capacitance parameters are extracted, the second section will extract the reverse Gummel parameters IS , VLR , IBR , BRI , RCV , RBV , RCC , and RBC . Then the third section will extract the reverse output characteristic parameter VER .

The fourth section is used to refine all parameters extracted in the previous two sections.

As the forward operation of the transistor is more important than the reverse, these model parameters are extracted last. In this way, the goodness of fit to the reverse data can be sacrificed if necessary to achieve the best fit to the forward data.

The fifth section extracts the parameters IS , BF , IBF , MLF , RE , IK to fit to the forward Gummel data, and the sixth section extracts the model parameter VEF to fit to the forward output characteristics.

Finally, the last section is used to refine all forward mode parameters that have been extracted in the previous two sections.

On completion of the sequence, the measured versus simulated characteristics should be as shown in opt_ex17_03.png . The model card can then be exported into an external model library file as shown in the output file opt_ex17.lib.

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