# New RF MOSFET Small Signal SPICE Model Part 2

Ickjin Kwon, Minkyu Je, Kwyro Lee, and Hyungcheol Shin Department of Electrical Engineering, Korea Advanced Institute of Science and Technology

Parameter Extraction Procedure

RF MOSFET Small - Signal Model and Parameters
Small-signal equivalent circuit of MOSFET after de-embedding parasitics is shown in Figure 1 and small-signal model parameters are listed in Table 1.

Figure 1. Common-source equivalent circuit of a
MOSFET after de-embedding parasitics of

Parameter Extraction Strategy
Parameter extraction is performed from real and imaginary parts of the Y-parameters. Each parameter is extracted from the Y-parameter equations which contain frequency terms.

To fit a straight line to the data plot, linear regression is used.

With the X data, the independent variable, and the Y data, the dependent variable, the estimated linear regression model is stated;

where the parameters, A and B, are estimated by the method of least squares.

A is the intercept :

B is the slope :

The standard deviation is defined as Where (Xi,Yi) are the data points,

N is the number of data points,

Parameters such as Cgd, Cgs, Rg, Cdg, Cjd, and Cds are extracted as a function of frequency and in these cases the extracted values are determined by their mean value. The mean of parameter is calculated by

where Pi are the extracted parameter values as a function of frequency.

Extraction Routine

* Note that, w = 2 <-> <-> .

Step 1.

gm is obtained from y-intercept of Re[Y21] versus .

Figure 2. Extraction results of gm.

Step2.

gds is obtained from y-intercept of Re[Y22] versus .

Figure 3. Extraction results of gds.

Step 3.

* Extracted Cgd is the mean value as a function of frequency.

Figure 4. Extraction results of Cgd.

Step 4.

* Extracted Cgs is the mean value as a function of frequency.

Figure 5. Extraction results of Cgs.

Step 5.

* Extracted Rg is the mean value as a function of frequency.

Figure 6. Extraction results of Rg.

Step 6.

* Extracted Cdg is the mean value as a function of frequency.

Figure 7. Extraction results of Cdg.

Step 6.

* Extracted Cdg is the mean value as a function of frequency. Step 7. Rsubd and Cjd are obtained from linear regression using the following relation.

Rsubd is determined from slope of Y as a function of .

Figure 8. Extraction results of Rsubd.

Step 8.

* Extracted Cjd is the mean value as a function of frequency.

Figure 9. Extraction results of Cjd.

Step 9.

* Extracted Cds is the mean value as a function of frequency

Figure 10. Extraction results of Cds.