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In most cases, the common-collector stage (emitter follower) is used as a buffer stage (unity gain). It is, therefore, an independent stage, whose mode of operation should not be determined by the ...
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#1: Initial revision
In most cases, the common-collector stage (emitter follower) is used as a buffer stage (unity gain). It is, therefore, an independent stage, whose mode of operation should not be determined by the next stage (which is to be decoupled). That means: Even without a connected load this stage should offer a low impedance output voltage. Therefore, it must have an emitter resistor RE, which allows the desired DC operating point.