Patent ID: 6246288
Filing Date: 2001-06-12
Classification: H03F

Abstract:
An operational amplifier comprising:a bias circuit that has a first resistor connected in series between a first source potential and a second source potential, and that generates and outputs a bias voltage through a reduction of a voltage at said first resistor;a differential stage that amplifies a difference between a first input voltage and a second input voltage and that outputs an output voltage;a level shift stage that has a first MOS transistor which is connected in series to a second resistor and which supplies a constant current controlled by said bias voltage, said level shift stage shifts a level of said output voltage by using a level shift voltage defined by a product of a current flowing through said second resistor and a resistance value of said second resistor and that outputs a level shift output voltage; anda push/pull-type output stage that has a second MOS transistor which is connected between said first source potential and an output node, and which is controlled by said output voltage, and that has a third MOS transistor which is connected between said output node and said second source potential and which is controlled by said level shift output voltage.