Patent ID: 6859100

Claim:
A class-A amplifier circuit having output voltage varied according to input voltage comprising: a class-A amplifier; a voltage pull-up switch level circuit for generating a pull-up switch level; a voltage pull-up circuit for pulling up an output voltage of the class-A amplifier; a voltage pull-up switch circuit for comparing the output voltage of the class-A amplifier with the pull-up switch level, and for driving the voltage pull-up circuit to pull up the output voltage of the class-A amplifier when the output voltage of the class-A amplifier is lower than the pull-up switch level; a voltage pull-down switch level circuit for generating a pull-down switch level; a voltage pull-down circuit for pulling down the output voltage of the class-A amplifier; and a voltage pull-down switch circuit for comparing the output voltage of the class-A amplifier with the pull-down switch level and for driving the voltage pull-down circuit to pull down the output voltage of the class-A amplifier when the output voltage of the class-A amplifier is higher than the pull-up switch level.