The small-signal equivalent diagram of the MOS transistor

 

As we want to perform small-signal analyses of analog CMOS circuits, we need a linearised model of a MOS transistor. Given an operating point, i.e. terminal voltages and currents, we must find dependences between small variations of these terminal voltages and currents. All formulas in this section apply to N-channel transistors; with regard to P-channel transistors, the signs must be changed at appropriate places.

  
Figure 3.1: Operating point of a MOS transistor.

 
• Low frequency model (saturation)
• Low frequency model (linear region).
• Capacitances of the small-signal equivalent diagram
• Summary and typical values