Noise Model

There are two noise models implemented in BSIM3—a conventional noise model named Spice2 model and a newly formulated noise model, which is referred to as BSIM3v3 noise model. The following equations and diagrams should give insight into these two noise formulations.

Please use the model bsim3_tutor_ac_noise.mdl provided with the BSIM3v3 Modeling Package to visualize the model parameters. Load the file into IC-CAP and run the different macros to see how certain parameters affect the device behavior of a deep submicron MOS transistor.

Conventional Noise Model for MOS Devices

Flicker noise:

(125)

Channel thermal noise:

(126)

Figure 133 Influence of AF on Effective Noise Voltage

Figure 134 Influence of EF on Effective Noise Voltage

BSIM3v3 Noise Model

The BSIM3v3 noise model uses the following equation to describe the flicker noise:

(127)

where:

No is the charge density at the source given by:

(128)

Nl is the charge density at the drain given by:

(129)

The channel thermal noise is given by:

(130)

with:

(131)