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Is it true that voltage between collector and emitter is 0 in the emitter follower configuration? (We intentionally use the saturation region of the transistor)?

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Absolutely not! Vce is whatever it needs to be, in order that the emitter remains Vbe below the base.

One use for the emitter follower is as a buffer, to isolate lhe load on the emitter from whatever voltage is present on the collector.

So with Vin=5.7V, Vout will be (approximately) 5V whether Vc is 6V, 12V, or 100V (given a suitable transistor), and Vce would be 1V, 7V or 95V in these cases.

Of course, if the collector voltage falls below 5.2V in this example, it no longer works (drawing the emitter current from Vin instead).

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  • \$\begingroup\$ So in case I have a resistor between collector and power Rc, Vce = Vcc - Ic(Rc+ Re)? \$\endgroup\$ Commented Jan 18, 2016 at 23:05
  • \$\begingroup\$ Ignoring the (small) base current, and assuming that calculation yields a positive Vce, yes. If Rc is too high, see the last sentence of answer. \$\endgroup\$
    – user16324
    Commented Jan 18, 2016 at 23:07

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