Input buffer and method for operating the same

A method for operating an input buffer, comprising:

• inputting a supply voltage at a first node where first and second transistors of a current mirror circuit are coupled with each other;
• generating, by a current source, a first current flowing through the first transistor;
• outputting, by the second transistor, in response to the supply voltage and the first current, a second current, to generate a first voltage at a second node between the current mirror circuit and a first amplifier;
• generating, in response to the first voltage and a reference voltage received at a gate terminal of a third transistor, a third current flowing through a first path, and generating, in response to the first voltage and an oscillating input signal received at a gate terminal of a fourth transistor, a fourth current flowing through a second path, wherein the first path and the second path are in parallel in the first amplifier and between the second node and a ground terminal, wherein the gate terminal of the third transistor is separated from the gate terminal of the fourth transistor;
• and
• generating a second voltage and a third voltage according to the third current and the fourth current.