AC model of Cascode Amplifier

This is just to demonstrate the principle of the cascode amplifier, without biasing circuitry ( hence it won't work if you try to run the simulation ) Common emitter amplifier ( Left transistor ) feeds common base amplifier ( Right transistor ) as the base of the Right transistor is grounded there is no miller effect upon Ccb. Same with the Left transistor as its collector is at a fixed DC voltage ( equivalent to ground for AC signals ) therefore there is no miller effect on Ccb in this transistor. By eliminating the miller effect the maximum frequency that can be amplified increases considerably.

published 8 years ago