The cascode amplifier is the two stage amplifier in which common emitter stage is connected to common base stage.

The CE-CB cascode connection is as shown in the figure:

Common emitter amplifier is used to achieve high voltage gain but when the application where large frequency range is required ,CE amplifier is not a choice as it reduces the band width at high frequencies due to introduction of miller's effect.

In case of cascode amplifier common emitter is heavily loaded by common-base stage reducing the gain to unity thus increasing bandwidth hence the gain bandwidth product is constant. Due the CB stage, the Miller capacitance of the transistor which becomes effective only at high frequencies is minimized by limiting the voltage gain of the amplifier to 1.

Hence CE-CB cascode provides more bandwidth than cascaded configuration.