Abstract: A vehicle key system is configured to change a lock status of a vehicle through communication performed between a user terminal and the vehicle. The vehicle key system includes one or more control circuits. The user terminal includes a terminal communication unit. The terminal communication unit is configured to communicate with the vehicle. The vehicle includes a vehicle communication unit and a vehicle opening-and-closing unit. The vehicle communication unit is configured to communicate with the user terminal. The one or more control circuits is configured to cause communication between the terminal communication unit and the vehicle communication unit to be stopped when an operation for putting the vehicle opening-and-closing unit into a locked state is performed, with the user terminal placed inside the vehicle.

Abstract: A valet key distribution system distributes key information of a vehicle among the vehicle, an owner terminal, and a guest terminal. The vehicle includes a vehicle-side storage storing a vehicle-side owner private key, a vehicle-side distribution key, a vehicle-side variable value, and a vehicle-side one-time password; and a vehicle-side controller controlling running of the vehicle and performing information processing. The owner terminal includes an owner-terminal input unit receiving an operation instruction from a utilization manager of the vehicle; an owner-side storage storing a terminal-side owner private key, a terminal-side distribution key, a terminal-side variable value, and a terminal-side one-time password; and an owner-side controller performing information processing.

Abstract: An amplifier circuit includes a first MOS transistor whose source is connected to a first power source and which amplifies a signal that is input to a gate and outputs the amplified signal from a drain, a second MOS transistor whose source is connected to the first power source, and a back gate voltage control element that controls the voltage a back gate of the second MOS transistor so that the voltage associated with the drain of the second MOS transistor and the voltage of the gate of the second MOS transistor are equal to each other, and which applies the controlled voltage to the back gate of the first MOS transistor.