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Comments on Purpose of emitter resistor in a common collector amplifier

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Purpose of emitter resistor in a common collector amplifier

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I see a lot of common collector amplifiers with the output taken across an emitter resistor.

What is the purpose of doing it this way instead of connecting your load directly to the emitter?

I should mention that I am referring to an emitter follower biased by the collector output of a previous common emitter stage.

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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 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.

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General comments (2 comments)
General comments
Circuit fantasist‭ wrote about 4 years ago

So, we can simply say that it behaves as an "ideal" (perfect, constant, steady) voltage source?

LvW‭ wrote about 4 years ago

Not "ideal" - but "idealized" and as "good" as possible with such a simple arrangement.