Difference between bipolar junction transistor amplifier and field effect transistor amplifier?

Answer 1

Bipolar transistors are so named because in which holes & electrones takes part in conduction.as opposed to unipolar transistors, such as field-effect transistors, in which only one type of Majority carrier takes part in conduction. FET Advantage over BJT FET requires vertually no input corrent and gives extreamly high input resistance.

FET's have a 4th source called a body and are a little bit more complicated the simple emitter, base, and collector of BJT's. they are more semiconductor and can't handle as much power as BJT.

http://en.wikipedia.org/wiki/Field_effect_transistor

http://en.wikipedia.org/wiki/Bipolar_junction_transistor

Answer 2

bipolar transistors drive current vertically as opposed to fets which go horizontally. because the dies are flat bipolar has a much larger current flow area. Think of the bipolar as a wedding cake where the collector, base, and emitter are all on stacked up on each other. current flows straight down yielding quick switching and power to driver other devices. fets have the collector, gate, drain side by side. the gate separates the collector and drain and it more like a flood gate prevent current to flow through. The problem is the current sees a thin surface area to drive through. The good thing about fets is its lower power consumption due to the circuit they are used. bipolar uses a circuit which is known as CML or current mode logic. In this case the current is always flowing and logic changes due to the change in the flow.