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A cascode stage is normally used at high (RF) frequencies to eliminate the miller capacitance effect between the transistor collector and base. The CB stage keeps the collector AC voltage of the CE stage near 0V so there is little AC negative feedback (feedback is undesirable) through the collector-base parasitic capacitance.
A cascode amp can change the DC level, but so do alot of amplifier configurations. The purpose of the cascode configuration, however, is to affect high gain at high frequency.
A cascode amplifier consists of a common emitter stage feeding a common base stage. Since the common base stage has the base grounded, the AC voltage at the collector of the CE stage, as ckshivaram mentioned, is very close to zero. It is the variation of the base-emitter diode of the CB stage vs emitter current. Historically, the name "cascode" dates back to the vacuum tube days; it's a contraction of "cascaded triode."
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