Abstract:
A display device capable of keeping the luminance constant irrespective of temperature change is provided as well as a method of driving the display device. A current mirror circuit composed of transistors is placed in each pixel. A first transistor and a second transistor of the current mirror circuit are connected such that the drain current of the first transistor is kept in proportion to the drain current of the second transistor irrespective of the load resistance value. The drain current of the first transistor is controlled by a driving circuit in accordance with a video signal and the drain current of the second transistor is caused to flow into an OLED, thereby controlling the OLED drive current and the luminance of the OLED.
Abstract:
In the microcomputer in the alarm device, supply of power to a sensor portion or a CPU in a sensor is allowed or stopped by a power gate controlled by a power gate controller. In addition, a volatile memory portion and a nonvolatile memory portion are provided in the CPU, data of the volatile memory portion is stored in the nonvolatile memory portion before supply of power to the CPU is stopped, and the data of the nonvolatile memory portion is restored to the volatile memory portion after the supply of power to the CPU is resumed. Thus, during an interval between measurement periods, supply of power to the sensor portion and the CPU can be stopped, so that low power consumption can be achieved compared with the case where power is continuously supplied.
Abstract:
An object is to provide a semiconductor device with a novel structure in which stored data can be retained even when power is not supplied, and does not have a limitation on the number of times of writing operations. A semiconductor device includes a source-bit line, a first signal line, a second signal line, a word line, and a memory cell connected between the source-bit lines. The memory cell includes a first transistor, a second transistor, and a capacitor. The second transistor is formed including an oxide semiconductor material. A gate electrode of the first transistor, one of a source and drain electrodes, and one of electrodes of the capacitor are electrically connected to one another. The source-bit line and a source electrode of the first transistor are electrically connected to each other. Another source-bit line adjacent to the above source-bit line and a drain electrode of the first transistor are electrically connected to each other.
Abstract:
An object of the present invention is to provide a driver circuit including a normally-on thin film transistor, which driver circuit ensures a small malfunction and highly reliable operation. The driver circuit includes a static shift register including an inverter circuit having a first transistor and a second transistor, and a switch including a third transistor. The first to third transistors each include a semiconductor layer of an oxide semiconductor and are depletion-mode transistors. An amplitude voltage of clock signals for driving the third transistor is higher than a power supply voltage for driving the inverter circuit.
Abstract:
An object is to achieve low power consumption and a long lifetime of a semiconductor device having a wireless communication function. The object can be achieved in such a manner that a battery serving as a power supply source and a specific circuit are electrically connected to each other through a transistor in which a channel formation region is formed using an oxide semiconductor. The hydrogen concentration of the oxide semiconductor is lower than or equal to 5×1019 (atoms/cm3). Therefore, leakage current of the transistor can be reduced. As a result, power consumption of the semiconductor device in a standby state can be reduced. Further, the semiconductor device can have a long lifetime.
Abstract:
To provide a novel nonvolatile latch circuit and a semiconductor device using the nonvolatile latch circuit, a nonvolatile latch circuit includes a latch portion having a loop structure where an output of a first element is electrically connected to an input of a second element, and an output of the second element is electrically connected to an input of the first element; and a data holding portion for holding data of the latch portion. In the data holding portion, a transistor using an oxide semiconductor as a semiconductor material for forming a channel formation region is used as a switching element. In addition, an inverter electrically connected to a source electrode or a drain electrode of the transistor is included. With the transistor, data held in the latch portion can be written into a gate capacitor of the inverter or a capacitor which is separately provided.
Abstract:
An object is to reduce leakage current and parasitic capacitance of a transistor used for an LSI, a CPU, or a memory. A semiconductor integrated circuit such as an LSI, a CPU, or a memory is manufactured using a thin film transistor in which a channel formation region is formed using an oxide semiconductor which becomes an intrinsic or substantially intrinsic semiconductor by removing impurities which serve as electron donors (donors) from the oxide semiconductor and has larger energy gap than that of a silicon semiconductor. With use of a thin film transistor using a highly purified oxide semiconductor layer with sufficiently reduced hydrogen concentration, a semiconductor device with low power consumption due to leakage current can be realized.
Abstract:
To individually control supply of the power supply voltage to circuits, a semiconductor device includes a CPU, a memory that reads and writes data used in arithmetic operation of the CPU, a signal processing circuit that generates an output signal by converting a data signal generated by the arithmetic operation of the CPU, a first power supply control switch that controls supply of the power supply voltage to the CPU, a second power supply control switch that controls supply of the power supply voltage to the memory, a third power supply control switch that controls supply of the power supply voltage to the signal processing circuit, and a controller that at least has a function of controlling the first to third power supply control switches individually in accordance with an input signal and instruction signals input from the CPU and the signal processing circuit.
Abstract:
In a display device such as a liquid crystal display device, a large-sized display screen is realized under low power consumption. A surface of a source wiring line of a pixel portion employed in an active matrix type liquid crystal display device is processed by way of a plating process operation so as to lower a resistance value of this source wiring line. The source wiring line of the pixel portion is manufactured at a step different from a step for manufacturing a source wiring line of a drive circuit portion. Further, electrodes of a terminal portion are processed by a plating process operation so as to reduce a resistance value thereof.
Abstract:
A display device is manufactured with five photolithography steps: a step of forming a gate electrode, a step of forming a protective layer for reducing damage due to an etching step or the like, a step of forming a source electrode and a drain electrode, a step of forming a contact hole, and a step of forming a pixel electrode. The display device includes a groove portion which is formed in the step of forming the contact hole and separates the semiconductor layer.