SELF-BIASED OPERATIONAL AMPLIFIER CIRCUIT, AND SAMPLE AND HOLD CIRCUIT COMPRISING THEREOF

PURPOSE: An operational amplifier circuit and an analog-digital convertor having the operational amplifier circuit is to reduce the noise and crosstalk phenomena due to a bias supply line. CONSTITUTION: An operational amplifier circuit comprises a first and a second differential inputs(110,120), a cas code current source(150) and a cas code current mirror(140). The first differential input comprises first differential input pairs to receive differential input signals and first differential output pairs including a first and a second differential outputs. The as code current source comprises second differential input pairs connected to the first differential output pairs, a first as code current source connected to the first output of the operational amplifier circuit and a second as code current source connected to the second output of the operational amplifier circuit. The as code current mirror comprises a first mirror current source connected to the first output of the operational amplifier circuit, a second mirror current source connected to the second output of the operational amplifier circuit and second differential output pairs including a third and a fourth differential outputs. The first differential input, the as code current source and the as code current mirror are self-biased in the requested operational state.