A Short Study on the Validity of Miller´s Theorem Applied to Transistor Amplifier High-Frequency Performance

The use of Miller´s theorem in the determination of the high-frequency cutoff frequency of transistor amplifiers was recently challenged by a paper published in this transactions. Unfortunately, that paper provided no simulation or experimental results to bring credence to the challenge or to validate the alternate method of determination proposed. This paper provides SPICE simulation results that validate the common usage of Miller´s theorem, limit the alternate method provided in that recent paper to a very small class of amplifiers, and reinforce the need to consider transistor amplifiers as two-pole systems.