Abstract: A substrate including a semiconductor layer, where characteristics of an element can be evaluated with high reliability, and an evaluating method thereof are provided. A substrate including a semiconductor layer of the invention has a closed-loop circuit in which an antenna coil and a semiconductor element are connected in series, and a surface of an area over which the circuit is formed is covered with an insulating film. By using such a circuit, a contactless inspection can be carried out. Further, a ring oscillator can be substituted for the closed-loop circuit.

Abstract: In electric power supply through wireless signals, electric power is supplied efficiently, even when distance fluctuation is caused between an electric power transmitting device and an electric power receiving device. Even when distance fluctuation is caused between the electric power transmitting device for supplying electric power with the use of wireless signals and the electric power receiving device for receiving electric power supplied from the electric power transmitting device, the Q value of the electric power transmitting device is adjusted to optimize the transmission efficiency. The impedance of a resonance circuit of the electric power transmitting device is fluctuated at a constant frequency, the resulting reflected wave is detected as a response signal by the electric power transmitting device, and the Q value of the electric power transmitting device is adjusted to optimize the transmission efficiency.

Abstract: An object is to provide a wireless power feeding system using the resonance method, which can increase power transmission efficiency. The wireless power feeding system includes a power transmission coil electrically connected to a high-frequency power supply, a power transmission resonance coil for transmitting power by electromagnetic induction with the power transmission coil, a power reception resonance coil for exciting high-frequency power by magnetic resonance, a load coil for exciting high-frequency power by electromagnetic induction with the power reception resonance coil, a load, and a variable element. The load includes a microprocessor for controlling the impedance of the load, a battery charger, and a battery. The battery charger is configured to charge the battery with the high-frequency power excited by the load coil.

Abstract: A wireless power feed system with high transfer efficiency of electric power is disclosed. The wireless power feed system includes a power feeding device and a power receiving device, wherein the power feeding device includes a first electromagnetic coupling coil that is connected to an AC power source via a directional coupler; a first resonant coil; a switch connected to the opposite ends of the first resonant coil; a control circuit which conducts switching on/off of the switch based on a parameter of an amplitude of a reflective wave detected by the directional coupler; and an analog-digital converter provided between the first electromagnetic coupling coil and the control circuit; and the power receiving device includes a second resonant coil; and a second electromagnetic coupling coil, and wherein the first electromagnetic coupling coil is provided between the first resonant coil and the second resonant coil.

Abstract: An object is to provide a photosensor utilizing an oxide semiconductor in which a refreshing operation is unnecessary, a semiconductor device provided with the photosensor, and a light measurement method utilizing the photosensor. It is found that a constant gate current can be obtained by applying a gate voltage in a pulsed manner to a transistor including a channel formed using an oxide semiconductor, and this is applied to a photosensor. Since a refreshing operation of the photosensor is unnecessary, it is possible to measure the illuminance of light with small power consumption through a high-speed and easy measurement procedure. A transistor utilizing an oxide semiconductor having a relatively high mobility, a small S value, and a small off-state current can form a photosensor; therefore, a multifunction semiconductor device can be obtained through a small number of steps.

Abstract: A power receiving device includes a resonant coil, an electromagnetic coupling coil, a rectifier circuit, a smoothing circuit, a voltage converter circuit which converts a voltage value of DC power into another voltage value, a control circuit which obtains voltage and current values of the DC power input to the voltage converter circuit, calculates an impedance from the obtained voltage and current values, and generates a pulse width modulation signal for controlling an output voltage and an output current of the voltage converter circuit, and a load to which the output voltage and the output current of the voltage converter circuit are input. The duty ratio of the pulse width modulation signal is determined so that the impedance calculated by the control circuit becomes close to an impedance for the maximum efficiency in transferring the AC power. The power receiving device is included in a contactless power feeding system.

Abstract: An object is to provide a wireless power feeding system using the resonance method, which can increase power transmission efficiency. The wireless power feeding system includes a power transmission coil electrically connected to a high-frequency power supply, a power transmission resonance coil for transmitting power by electromagnetic induction with the power transmission coil, a power reception resonance coil for exciting high-frequency power by magnetic resonance, a load coil for exciting high-frequency power by electromagnetic induction with the power reception resonance coil, a load, and a variable element. The load includes a microprocessor for controlling the impedance of the load, a battery charger, and a battery. The battery charger is configured to charge the battery with the high-frequency power excited by the load coil.

Abstract: A resonant power feeding system that can provide high power transmission efficiency between a power feeding device and a power reception device without dynamically controlling the oscillation frequency in accordance with the distance between the power feeding device and the power reception device. High power transmission efficiency between the power feeding device and the power reception device is obtained by addition of a structure for adjusting the matching condition to both the power reception device and the power feeding device. Specifically, a transmission-reception circuit and a matching circuit are provided in both the power reception device and the power feeding device, and wireless signals for adjusting the matching circuit are transmitted and received through a resonant coil. Thus, the power feeding device can efficiently supply power to the power reception device without adjusting the oscillation frequency.

Abstract: One object of the present invention is to provide a regulator circuit with an improved noise margin. In a regulator circuit including a bias circuit generating a reference voltage on the basis of the potential difference between a first power supply terminal and a second power supply terminal, and a voltage regulator outputting a potential to an output terminal on the basis of a reference potential input from the bias circuit, a bypass capacitor is provided between a power supply terminal and a node to which a gate of a transistor included in the bias circuit is connected.

Abstract: A wireless power feeding system includes a power feeding device and a power receiving device. The power feeding device includes a first resonance coil connected to a high-frequency power source through a first matching circuit, and a first control circuit connected to the first matching circuit and a first transmitter-receiver circuit. The power receiving device includes a second resonance coil configured to be in magnetic resonance with the first resonance coil, and a second control circuit connected to a load, a second matching circuit, and a second transmitter-receiver circuit.

Abstract: To prevent damage on an element even when a voltage high enough to break the element is input. A semiconductor device of the invention operates with a first voltage and includes a protection circuit which changes the value of the first voltage when the absolute value of the first voltage is higher than a reference value. The protection circuit includes: a control signal generation circuit generating a second voltage based on the first voltage and outputting the generated second voltage; and a voltage control circuit. The voltage control circuit includes a transistor which has a source, a drain, and a gate, and which is turned on or off depending on the second voltage input to the gate and thus controls whether the value of the first voltage is changed based on the amount of current flowing between the source and the drain. The transistor also includes an oxide semiconductor layer.

Abstract: The contactless power feeding system includes a power transmitting device including an AC power source, a power transmitting element transmitting an AC power and a first microprocessor generating a transmission signal, and a power receiving device including a power receiving element receiving the AC power, a rectifier circuit, a smoothing circuit, a voltage conversion circuit, a second microprocessor generating a response signal in accordance with the transmission signal, a charge control circuit changing a charging rate for a power storage device in accordance with the response signal and the power storage device whose charging is controlled by the charge control circuit. Then, a resistance value of the power storage device changes, an impedance changes, and a modulation signal is generated. The generated modulation signal is transmitted from the power receiving device to the power transmitting device and is processed by the first microprocessor.

Abstract: A wireless power feed system with high transfer efficiency of electric power is disclosed. The wireless power feed system includes a power feeding device and a power receiving device, wherein the power feeding device includes a first electromagnetic coupling coil that is connected to an AC power source via a directional coupler; a first resonant coil; a switch connected to the opposite ends of the first resonant coil; a control circuit which conducts switching on/off of the switch based on a parameter of an amplitude of a reflective wave detected by the directional coupler; and an analog-digital converter provided between the first electromagnetic coupling coil and the control circuit; and the power receiving device includes a second resonant coil; and a second electromagnetic coupling coil, and wherein the first electromagnetic coupling coil is provided between the first resonant coil and the second resonant.

Abstract: It is an object to provide a gas sensor which is formed by a simple manufacturing process. Another object is to provide a gas sensor whose manufacturing cost is reduced. A transistor which includes an oxide semiconductor layer in contact with a gas and which serves as a detector element of a gas sensor, and a transistor which includes an oxide semiconductor layer in contact with a film having a gas barrier property and which forms a detection circuit are formed over one substrate by the same process, whereby a gas sensor using these transistors may be formed.

Abstract: A power feeding device utilizing an electromagnetic resonance coupling method and a contactless power feeding system can be provided. A coupling coefficient of electromagnetic induction coupling in the power feeding device and/or the inside of a power receiving device is optimized to improve electric power transmission efficiency of a resonance frequency regardless of positions of the power feeding device and the power receiving device. Provided is a power feeding device or a contactless power feeding system in which an S11 parameter which is a reflection component of electric power output from a high-frequency power source of the power feeding device is monitored, and one or both of positions of a transmission coil and a first resonant coil in the power feeding device and positions of a reception coil and a second resonant coil in a power receiving device are changed to adjust a coupling coefficient of electromagnetic induction coupling.

Abstract: A resonant power feeding system that can provide high power transmission efficiency between a power feeding device and a power reception device without dynamically controlling the oscillation frequency in accordance with the distance between the power feeding device and the power reception device. High power transmission efficiency between the power feeding device and the power reception device is obtained by addition of a structure for adjusting the matching condition to both the power reception device and the power feeding device. Specifically, a transmission-reception circuit and a matching circuit are provided in both the power reception device and the power feeding device, and wireless signals for adjusting the matching circuit are transmitted and received through a resonant coil. Thus, the power feeding device can efficiently supply power to the power reception device without adjusting the oscillation frequency.

Abstract: To prevent damage on an element even when a voltage high enough to break the element is input. A semiconductor device of the invention operates with a first voltage and includes a protection circuit which changes the value of the first voltage when the absolute value of the first voltage is higher than a reference value. The protection circuit includes: a control signal generation circuit generating a second voltage based on the first voltage and outputting the generated second voltage; and a voltage control circuit. The voltage control circuit includes a transistor which has a source, a drain, and a gate, and which is turned on or off depending on the second voltage input to the gate and thus controls whether the value of the first voltage is changed based on the amount of current flowing between the source and the drain. The transistor also includes an oxide semiconductor layer.

Abstract: A power feeding device utilizing an electromagnetic resonance coupling method and a contactless power feeding system can be provided. A coupling coefficient of electromagnetic induction coupling in the power feeding device and/or the inside of a power receiving device is optimized to improve electric power transmission efficiency of a resonance frequency regardless of positions of the power feeding device and the power receiving device. Provided is a power feeding device or a contactless power feeding system in which an S11 parameter which is a reflection component of electric power output from a high-frequency power source of the power feeding device is monitored, and one or both of positions of a transmission coil and a first resonant coil in the power feeding device and positions of a reception coil and a second resonant coil in a power receiving device are changed to adjust a coupling coefficient of electromagnetic induction coupling.

Abstract: It is an object to obtain a memory element (DRAM) storing multilevel data easily. The amount of charge accumulated in a capacitor of a memory element (DRAM) is controlled by changing the potential of a wiring (a bit line), which is used for writing data to the memory element (DRAM), in a period in which a transistor included in the memory element (DRAM) is on. Thus, multilevel data stored in the memory element (DRAM) can be obtained without a complex configuration of a semiconductor device including the memory element (DRAM).

Abstract: An object of the invention is to reduce the power consumption of a semiconductor device that requires a plurality of reference potentials and a method of driving the semiconductor device. Disclosed is a semiconductor device having a potential divider circuit in which a potential supplied to a power supply line is resistively divided by resistors connected in series to the power supply line so that a desired potential is output through a switch transistor electrically connected to the power supply line. A drain terminal of the switch transistor is electrically connected to a gate terminal of a transistor provided in a circuit on the output side (or to one terminal of a capacitor) to form a node. The switch transistor has an off current low enough to hold the desired voltage in the node even when the potential is no more supplied to the power supply line.