Model-Based Analog Circuit Design

Being able to analyze and design analog circuits using "hand analysis" allows us to build intuition, and this intuition enables us to create designs that are optimal and innovative. However:

• Our simple models such as the square-law model or velocity-saturation model, cannot accurately describe the behavior of key parameters such as output resistance, $r_{o}$, or completely misses operating regions such as the moderate inversion region.
• Using more accurate and complex models, such as BSIM, is ideal for verification, but not really suited for "hand analysis" since
  • We have to work with hundreds of parameters per transistor, or
  • Make many assumptions to reduce these parameters, but then only ending up in the same situation as using the simple models.

One solution around this problem is to use the simulator, in conjunction with the BSIM models, as a "calculator".

Design Parameters

In circuit design, we are normally interested in the following parameters:

• Gain
• Bandwidth
• Power
• Voltage Swing
• Noise

It turns out we can most of these parameters by using our BSIM models as lookup tables.