An Example of Fitting a Model to a Chip Transistor

A small-signal model will be fitted to a transistor (chip) in this example. The bias point and four boundary lines will also be specified to define the allowable intrinsic load-line area on the I/V-plane.

Small-signal models are used in MultiMatch to find the optimum power load for a transistor and also to calculate the output power obtainable from the transistor in a MultiMatch circuit.

The Settings Command should be used to set the correct Data, Working and Export Directories

The directories set

The File | Open Command is used to open a MultiMatch circuit file

The circuit file is selected

The schematic of the circuit opened

The FET Model Command is selected in the Analysis Menu

A name must be specified for the .s2p or the .spi S-parameter data file

The FHX04X.s2p data file will be opened

A MultiMatch Identifier must also be specified for the transistor

The Initialize command on the Intrinsic Page will be selected

The Y-parameters will be fitted by using a least-square error function

The frequency range can be changed by using the Modify Range Command

The S-parameters of the model (solid colors) are compared with the measured parameters (mixed color traces)

Bounds can be set on the element values before the model is optimized

The value of Rd is constrained here

Rs is constrained

The S-parameter fit will be optimized by using the L1 error function

The S-parameters of the model are compared with the measured parameters

The final values of the fitted intrinsic components

The dc operating point and the four boundary lines defining the intrinsic load-line area allowed on the I/V plane must be specified on this page

The bias point and the line parameters were specified for the FHX04X. The OK Command will be used to close the Wizard and to create the required model file.

The model has been fitted and can now be used in the circuit. This example will be terminated at this point.