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<\/p>\nQ.\u00a0<\/b>What is the recommended noise model in SPICE?<\/p>\n
A.\u00a0<\/b>NOISE MODEL EXTRACTION AND ANALYSIS OF NOISE MODELS IN SPICE:<\/p>\n
The traditional Noise models in SPICE used two parameters (AF and KF) to model the noise level and the frequency dependency of flicker noise in MOS devices. There are three different standard models and they can be activated using the noise level selector parameter NLEV in SPICE.<\/p>\n
Among these three models the NLEV=2 model is widely used. The NLEV=2 model incorporates the gm of the device into the noise model equation and provides a better fit compared to the NLEV=0 and NLEV=1 models. However none of these three standard models can model the DC bias dependency of flicker noise very well. Therefore a table with AF and KF values at different DC bias points is provided as a solution.<\/p>\n
In order to extract the AF and KF for NLEV=2 model the flicker noise data should be collected using the S3245A noise amplifier and\u00a0UTMOST III<\/b>\u00a0noise routine as explained in the last Simulation Standard issue.<\/p>\n
After the data collection is completed the Fit Variable “select_model” (Figure 1) should be set to 2 (selecting the NLEV=2 model) and the “Fit” button from the “Options” menu of the graphics screen should be pressed. (Figure 2) The AF and KF will be extracted and copied into the parameters screen. The parameter NLEV in the parameter screen should be set to 2 prior to the parameter extraction.<\/p>\n
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