Electronics Principles V11

Clive W. Humphris

TRANSISTOR CONFIGURATIONS: Emitter Follower Configuration.  

The diagram shows a simple Emitter Follower circuit, where owing to the transistor base-emitter junction, the emitter voltage will always be 0.6V below the base voltage. Because of the low value emitter resistor the circuit is able to supply high currents without upsetting the biasing caused by changes in the emitter voltage.

Other practical uses of this circuit are for impedance matching, where the base circuit has a high input impedance and the emitter a low output impedance. Thereby, enabling larger current loads to be driven than for a common emitter configuration.

There is no phase inversion between the base and emitter of a transistor, as the base is made more positive, increasing current flows between the emitter and collector, therefore there is a larger voltage developed across the emitter resistor and the emitter volts rise.

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