emitter follower is a type of negative feedback ,
I think you mean a common emitter amplifier, which is an amplifier of voltage. Emitter-follower or common collector amplifiers are used to match impedances, or to amplify power or current. The emitter-follower is a type of common emitter circuit that has a resistor between the emitter and ground. The output signal is taken from the point between the emitter and its resistor.
it is a mechanism applied in an amplifier so as to raise it's input impedance.Mostly this mechanism is applied in a common collector(emitter follower) amplifier.
Limit current through emitter, Often the resistance is the load itself. So the restatnce limits current on what otherwise would act as a voltage follower.
The advantage of the emitter follower is that it has a positive gain of 1.
An emitter resistor in a common emitter circuit will cause the stage to experience the effects of degenerative feedback if it is unbypassed. The degenerative feedback reduces gain. This is probably the primary effect in the described circuit.
The emitter resistor is connected to ground(in the case of an rc coupled amplifier).Also input signal applied at the base is grounded.Then the emitter resistor forms a feedback to the input signal (through the ground return path).So emitter resistor is also called feedback resistor.
negative feedback
With a common emitter amplifier it's the emitter that is usually grounded.
The emitter resistor in a common emitter configuration provides negative feedback to the transistor, reducing both its voltage gain and distortion.
In an NPN transistor an emiter follower refers to an amplifier topology. The emiter follower configuration is when the emitter of a N-Type Bipolar Junction Transistor (BJT) is connected to the common point on a circuit (typically ground). This is not always the case, however, because many amplifier configuration exist.
In a Voltage Shunt feedback Amplifier, the feedback signal voltage is given to base of transistor in shunt through a feedback resistor.This Shunt connection decreases the input input impedance and voltage feedback decreases the output impedance. In this amplifier input is current and output is voltage. Thus Transresistance is stabilized.Input and Output impedances are reduced by a factor of 'D'(desensitivity factor). Advantages: 1)Gain independent of device parameters. 2)Bandwidth increases. 3)Noise and non-Linear distortion decrease. 4)Prevents Loading effect. 5)Acts as good source for the next stage.