Abstract: An optical-pickup apparatus includes: a first laser light source including a first laser diode to emit a laser beam having a first wavelength, and a back-monitor photodetector to receive the laser beam emitted in a backward direction, not being an optical-disc direction, and output a first monitor signal; a second laser-light source including a second laser diode to emit a laser beam having a second wavelength; a light-receiving circuit including a front-monitor photodetector to receive the laser beam emitted in a forward direction, being the optical-disc direction, and output a second monitor signal, and a switch circuit to be inputted with the first and second monitor signals, and output the first or second monitor signal according to a switch signal; and first and second drive circuits to drive the first and second laser diodes according to the first and second monitor signals outputted from the light-receiving circuit, respectively.

Abstract: The invention provides a semiconductor device which has a capacitor element therein to achieve size reduction of the device, the capacitor element having larger capacitance than conventional. A semiconductor integrated circuit and pad electrodes are formed on the front surface of a semiconductor substrate. A second insulation film is formed on the side and back surfaces of the semiconductor substrate, and a capacitor electrode is formed between the back surface of the semiconductor substrate and the second insulation film, contacting the back surface of the semiconductor substrate. The second insulation film is covered by wiring layers electrically connected to the pad electrodes, and the wiring layers and the capacitor electrode overlap with the second insulation film being interposed therebetween. Thus, the capacitor electrode, the second insulation film and the wiring layers form capacitors.

Abstract: An optical-pickup apparatus includes: a first laser light source including a first laser diode to emit a laser beam having a first wavelength, and a back-monitor photodetector to receive the laser beam emitted in a backward direction, not being an optical-disc direction, and output a first monitor signal; a second laser-light source including a second laser diode to emit a laser beam having a second wavelength; a light-receiving circuit including a front-monitor photodetector to receive the laser beam emitted in a forward direction, being the optical-disc direction, and output a second monitor signal, and a switch circuit to be inputted with the first and second monitor signals, and output the first or second monitor signal according to a switch signal; and first and second drive circuits to drive the first and second laser diodes according to the first and second monitor signals outputted from the light-receiving circuit, respectively.

Abstract: The invention provides a semiconductor device which has a capacitor element therein to achieve size reduction of the device, the capacitor element having larger capacitance than conventional. A semiconductor integrated circuit and pad electrodes are formed on the front surface of a semiconductor substrate. A second insulation film is formed on the side and back surfaces of the semiconductor substrate, and a capacitor electrode is formed between the back surface of the semiconductor substrate and the second insulation film, contacting the back surface of the semiconductor substrate. The second insulation film is covered by wiring layers electrically connected to the pad electrodes, and the wiring layers and the capacitor electrode overlap with the second insulation film being interposed therebetween. Thus, the capacitor electrode, the second insulation film and the wiring layers form capacitors.

Abstract: In the current-controlled oscillator performing an oscillation frequency control by using a differential amplifier circuit, resistors are inserted to each current path of a differential pair of the differential amplifier circuit, and thereby an inclination of output currents Ia, Ib of a differential pair is small in the linear line region. Further, by setting a reference voltage applied to a base of a transistor of one side of the differential pair lowly, the linear region is shifted to low voltage side, and thereby a saturation region of the low voltage side is not occurred. Moreover, when a comparison result of a phase of an output signal of the current-controlled oscillation circuit and a reference signal is converted to an oscillation frequency control voltage Vtune, by limiting an upper limit voltage of the Vtune by an output of a regulator in stead of a positive voltage power source Vcc of common circuit, the Vtune does not move to a saturation region upper than the linear region.

Abstract: In the current-controlled oscillator performing an oscillation frequency control by using a differential amplifier circuit, resistors are inserted to each current path of a differential pair of the differential amplifier circuit, and thereby an inclination of output currents Ia, Ib of a differential pair is small in the linear line region. Further, by setting a reference voltage applied to a base of a transistor of one side of the differential pair lowly, the linear region is shifted to low voltage side, and thereby a saturation region of the low voltage side is not occurred. Moreover, when a comparison result of a phase of an output signal of the current-controlled oscillation circuit and a reference signal is converted to an oscillation frequency control voltage Vtune, by limiting an upper limit voltage of the Vtune by an output of a regulator in stead of a positive voltage power source Vcc of common circuit, the Vtune does not move to a saturation region upper than the linear region.

Abstract: To ensure establishment of synchronization and data demodulation among a number of transmitter/receivers using a spread spectrum method. Specifically, in a normal communication state, a second transmitter/receiver sends transmission data including a pilot carrier and a communication carrier. Receiving the transmission data, a first transmitter/receiver establishes synchronization between a spread code contained in the received spread spectrum signal and its own generated spread code, based on dummy data received during a pilot carrier period, and maintains the established synchronization. Thereafter, the first transmitter/receiver digitally demodulates data in the communication carrier. The resultant data is subjected to decoding and analog conversion to be converted into an audio signal. A control data is derived from the digitally demodulated data, and used to control the operation of the first transmitter/receiver.

Abstract: The PLL device includes means (6) for generating a, plurality of reference signals (FR1, FR2, FR3, FR4) having mutually differing phases, a variable frequency divider (11, 12, 13, 14) for dividing, in synchronization with the phases of a plurality of the reference signals, a frequency of an output signal (FO) of a voltage-controlled oscillator (15) that produces a signal having a frequency responsive to a control voltage (CV) supplied to generate a plurality of feedback signals (FV1, FV2, FV3, FV4) having mutually differing phases, phase comparators (7, 17, 8, 18, 9, 19, 10, 20) for comparing phases between the reference signals and the feedback signals corresponding to the reference signals respectively to produce a plurality of error signals (ER1, ER2, ER3, ER4), a low-pass filter (21) for filtering the error signals output from the phase comparators to produce the control voltage, and a control means (16, 26, 27) for controlling the number of the phase comparators that output the error signals to the low-p