Patent ID: 7187214
Filing Date: 2007-03-06
Classification: H03K

Abstract:
1. An amplifier circuit comprising: a first bias unit, which responds to an internal reference signal with a predetermined voltage level and maintains constant the amount of a first current; a second bias unit, which receives an external reference signal, responds to a control voltage, and controls the amount of a second current to be same as the amount of the first current; a comparison unit, which compares a voltage level of a first node of the first bias unit with a voltage level of a second node of the second bias unit and controls a voltage level of the control voltage according to the comparison result; and an amplifier unit, which compares a voltage level of an external input signal and a voltage level of the external reference signal, amplifies and outputs a voltage difference between the external input signal and the external reference signal, responds to the control voltage, and controls the amount of a third current to be same as the amount of the first current although the level of the external reference signal is varied.