Constant voltage circuit for improvement of load transient response with stable operation in high frequency, and electronic device therewith

An electronic device comprising a constant voltage circuit comprising an operational amplifier including a constant current source, the operational amplifier amplifying an error between a predetermined reference voltage and an output voltage, the constant voltage circuit controlling a load current based on an amplified voltage so that the output voltage is controlled to be a predetermined constant voltage, wherein the constant voltage circuit comprises:

• a voltage detector that detects only high frequency of an AC components of the output voltage limited to a predetermined band, and outputs a detected voltage;
• a voltage amplifier that amplifies AC components of the detected voltage and outputs the amplified voltage;
• a judgment circuit that outputs a judgment signal indicating whether or not the amplified voltage is equal to or larger than a predetermined threshold, based on the amplified voltage;
• and a controller configured to increase a current value of the constant current source of the operational amplifier based on the judgment signal, thereby temporarily increasing a current consumption of the operational amplifier.