Patent ID: 8098057

Claim:
A constant voltage circuit configured to convert an input voltage into an output voltage having a predetermined level, the constant voltage circuit comprising: a differential amplifier circuit configured to produce an output signal having a voltage level determined in response to a reference voltage and the output voltage; and an output circuit configured to receive the output signal and produce an output current in response to the voltage level of the output signal, the output voltage being proportional to the current, wherein the output circuit includes plural output transistors and a transistor selecting unit configured to select one or more output transistors to be operated among the plural output transistors to produce the current depending on the level of the output voltage; a supply unit having plural current sources to supply a bias current from at least one of the plural current sources to the differential amplifier circuit; and a determination circuit configured to receive the output voltage and select one or more current sources to be operated amongst the plural current sources depending on the level of the output voltage.