Input Resistance and Open Circuit Gain for Common Bipolar Junction Transistors

Here are some hybrid-pi models that demonstrate the small signal analysis of the common BJT configurations.  These equations are universal and can be applied to any resistor/capacitor scheme.  They can also be applied directly to MOSFETs.  Just replace Rc=Rd, Rb=Rg, Re=Rs, and Rpi=infinity.  Boom.

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