Patent ID: 8519782

Claim:
A constant voltage circuit comprising: a current source configured to generate a reference current; a depletion-type first MOSFET (Metal Oxide Semiconductor Field Effect Transistor) arranged such that one terminal thereof is connected to the current source, and the gate thereof is connected to the source thereof; an enhancement-type second MOSFET arranged such that one terminal thereof is connected to the other terminal of the first MOSFET, the other terminal thereof is connected to a first fixed voltage terminal such that a voltage potential at the other terminal of the second MOSFET is fixed, and the gate thereof is connected to the drain thereof; and an enhancement-type P-channel third MOSFET arranged such that one terminal thereof is connected to the current source, the other terminal thereof is connected to the first fixed voltage terminal, and the gate thereof is connected to a connection node that connects the first MOSFET and the second MOSFET, wherein the constant voltage circuit outputs at least one of a voltage that corresponds to the gate voltage of the third MOSFET and a voltage that corresponds to the source voltage of the third MOSFET.