Combining an NPN bipolar junction transistor (BJT) emitter follower with a PNP BJT emitter follower gives a voltage out that is almost exactly the same as the voltage in. There is no 0.6V diode shift within limits.

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The maximum voltage of the output will be about 1 volt shy of reaching the full supply voltage.

Diagram





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There is an NPN emitter follower in the circuit that outputs 0.6V lower than the voltage at the base.

The base (input) of the NPN emitter follower is connected to the output of a PNP emitter follower.

PNP emitter followers give a voltage that is 0.6V higher than it’s base voltage.

So, the PNP emitter follower raises the signal by 0.6V but the NPN emitter follower drops the signal voltage by 0.6V. Therefore the circuit output is at about the same voltage as the original Vin signal voltage.

Video

Quick improved BJT emitter follower circuit removing Vin to Vout diode drop by electronzap



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