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They seem like two words for the same thing, but I also see some sources have different configurations for them.

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  • \$\begingroup\$ Related: electronics.stackexchange.com/questions/311637/… \$\endgroup\$
    – MarkU
    Nov 7, 2017 at 5:04
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    \$\begingroup\$ Common Emitter configuration means base is the input, collector is output, and emitter is the common. But Emitter Follower is a Common Collector configuration: the base is the input, emitter is the output, and the collector is the common. \$\endgroup\$
    – MarkU
    Nov 7, 2017 at 5:04

2 Answers 2

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When we talk about common emitter, common base, and common collector configurations, the terminal that's named as "common" is the one that isn't used for input or output. It's the one that's used as a ground or "common" terminal by both the input and output of the circuit.

An emitter follower has input into the base and output from emitter of the transistor. It's a common collector circuit, not common emitter.

A common emitter circuit has input into the base, and output from the collector of the transistor.

Whatever source you found that says that common emitter and emitter follower are synonyms is simply incorrect.

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  • \$\begingroup\$ Is the word "amplifier" omitted? Is a common collector also a common collector amplifier? \$\endgroup\$
    – james
    Nov 7, 2017 at 5:19
  • \$\begingroup\$ Yes, "common collector amplifier", "common collector circuit", and "common collector configuration" mean the same thing. \$\endgroup\$
    – The Photon
    Nov 7, 2017 at 5:34
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Common Emitter can produce voltage gain >> one.

Common Collector (aka emitter follower) produces voltage gain slightly less than one.

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