Kunal Kandekar wrote:
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I am aware of comparison between the various transistor configurations, I just wish to know the advantage of the Common-Emitter over the Emitter-Follower in this application. Wouldn't higher current gain be needed to drive a motor?

The emitter follower has the advantage of high current gain, but at the expense of the required drive voltage: since Vbe is always close to 0.6 V, the voltage on the base will be Ve +0.6 volts. If you only have a 5V supply, then you can only get 4.4 volts on the load. Full stop. Darlington transistor ? no difference.

The common emitter configuration does not suffer from that, - Vload can be varied from zero to Vcc - a couple of volts, but is harder to stabilise with real world considerations- you ideally need an emitter degenerating resistor to cut the gain down and stabilse the operating points with temperature.



Steve