why common emitter configuration is most widely used as an amplifier

hi...

why common emitter configuration is most widely used as an amplifier

IT is easy to bias and it has the most gain.

(I would like to point out, that for high-frequency class-C amplifiers, Common-Base is really popular for NPN Bipolar transistors. Of course, the biasing is pretty easy...)

thx buddy

diaryrashid: hi...

why common emitter configuration is most widely used as an amplifier

Because it shows the highest gain for a given transistor. Common collectors have a voltage gain of 1 and a common base has a low gain.

Because you can easily control a device, like a relay/etc, that needs much higher current than a microcontroller I/O pin can supply. In general, a 5V pin cannot provide enough current to even drive a common 5V relay.

In addition, it allows you to control devices that require different voltage levels, such as a 12V relay.

That's for simple on-off control. If you want to actually amplify "signals", that's something else again, in which case you want a more reliable amplification-value, see Emitter degeneration section here, http://en.wikipedia.org/wiki/Common_emitter