Rohm Co., Ltd.

Hiroyuki Funahashi

Ichiro Yokomizo

Isao Yamamoto

Koji Nishikawa

Chung Chien San

Ayumu Ibusuki

A signal generating circuit of the invention includes a current polarity switch circuit that receives an output current of a light-sensitive element and outputs a current of which the direction the polarity switch circuit keeps constant regardless of the direction of the received current, a current-to-voltage conversion circuit that converts the current outputted from the current polarity switch circuit into a voltage, and a signal processing circuit that receives the voltage outputted from the current-voltage conversion circuit to generate a signal based on the received voltage. Thus, the signal based on the received current signal can be generated regardless of the direction of the received current signal.

Signal generating circuit and optical pickup device provided therewith

To realize a current-to-voltage conversion IC and a photoelectric conversion IC in which the available frequency range does not become narrower as the conversion gain is increased, in a current-to-voltage conversion IC that has a differential amplifier to which a negative feedback resistor of variable resistance is connected and a photodiode connected to the input terminal of the differential amplifier so that the output current of the photodiode is converted into a voltage by means of the negative feedback resistor, the differential amplifier is provided with a switch for varying the capacitance of a capacitor used as a phase compensating element so that the resistance of the negative feedback resistor and the capacitance of the differential amplifier are varied in an interlocked manner in accordance with a signal fed from outside.

Current-to-voltage conversion IC and a photoelectric conversion IC

An equalizer includes first and second differential amplifiers which have a common output and respective separate current sources, a first negative feed back circuit which feeds back a voltage signal extracted from the common output to the first differential amplifier, a second negative feed back circuit which feeds back the voltage signal to the second differential amplifier, and a filter circuit which is provided at either the first or the second negative feed back circuit and which differentiates frequency characteristics during signal amplification in the first and second differential amplifiers. Frequency characterstic is selected through selection of one of the current values of the respective current sources in response to a sound quality adjusting signal.

Equalizer and audio device using the same

An equalizer includes first and second differential amplifiers which have a common output and respective separate current sources, a first negative feed back circuit which feeds back a voltage signal extracted from the common output to the first differential amplifier, a second negative feed back circuit which feeds back the voltage signal to the second differential amplifier, and a filter circuit which is provided at either the first or the second negative feed back circuit and which differentiates frequency characteristics during signal amplification in the first and second differential amplifiers. A frequency characteristic is selected through selection of one of the current values of the respective current sources in response to a sound quality adjusting signal.

The apparatus includes output stage amplifiers for receiving the respective outputs of preamplifiers provided in correspondence to the left and right channels in a stereo system. Negative feedback circuits are provided in the respective output stage amplifiers for reducing the amount of low-band negative feedback. Switch circuits are turned on in response to feedback signals from the respective negative feedback circuits for supplying the feedback signals at the input to the output stage amplifiers.

Low-voltage driven, audio signal amplifying apparatus and a portable

A power amplifier of a digital cassette tape reproducing device is set to a value suitable to amplify an amplitude level of an audio signal from an analog signal reproducing system thereof and, when a digital signal reproducing system is selected, an audio signal therefrom is supplied to the power amplifier circuit without attenuation while increasing an amount of negative feedback of the power amplifier circuit, hence reducing amplification thereof to match an output level of the power amplifier circuit with that of the analog signal reproducing system to thereby improve S/N ratio and maintain high tone quality of the digital source.

Digital cassette tape reproducing device including novel drive circuit

A isolation amplifier circuit comprises: an operation amplifier provided with a first and second input terminals, an output terminal, and a feedback resistor for connecting the output terminal and second input terminal; a first emitter follower, for inputting a signal, connected to the first input terminal; a second emitter follower connected between the output terminal and the feedback resistor; a third emitter follower connected between the second input terminal and a first ground impedance; and a fourth emitter follower connected between the first input terminal and a second ground impedance. In the isolation circuit, dynamic resistances of the first, second, third, and fourth emitter followers are made identical with one another.

Growing community of inventors

Kyoto, Japan

Hiroyuki Funahashi