Source follower and current feedback circuit thereof

A source follower, comprising:

• a transistor, comprising a first electrode, a second electrode, and a third electrode, wherein the first electrode receives an input signal, the second electrode outputs an output signal according to the input signal, and a drain current flows by the transistor;
• an impedance, coupled to the third electrode to form a first node, wherein the drain current flows through the impedance and the first node outputs an error voltage which is corresponding to the drain current;
• a comparator, coupled to the impedance for comparing the error voltage with a reference voltage and thereby outputting a reference current;
• a feedback circuit, for feeding back the reference signal to the source follower, wherein the source follower adjusts the drain current according to the reference signal.

A method for receiving an input signal and thereby outputting an output signal, the method comprising:

• receiving the input signal by a gate of a transistor, and thereby outputting the output signal according to the input signal by a source of the transistor, wherein a drain current flows through the transistor;
• generating an error voltage which is corresponding to the drain current and an impendence;
• comparing the error voltage with a reference voltage and thereby outputting a reference signal;
• and
• adjusting the drain current according to the reference signal.