Light receiving amplifying device
First Claim
1. A light receiving amplifying device, comprising:
- a light receiving device for outputting a light signal current which varies with a quantity of received light;
a load resistor, connected with said light receiving device in series, for generating a detected voltage which varies with the light signal current;
a low frequency current bypass circuit, being connected with said load resistor in parallel and exhibiting a high input impedance with respect to the detected voltage in a high frequency band, for preventing the detected voltage in a low frequency band from being saturated;
a transimpedance amplifying circuit for transforming an impedance of the detected voltage; and
a capacitor for coupling said low frequency current bypass circuit and said transimpedance amplifying circuit.
1 Assignment
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Accused Products
Abstract
A light receiving amplifying device includes a light receiving device for outputting a light signal current which varies with a quantity of received light, a load resistor connected with the light receiving device in series, for generating a detected voltage which varies with the light signal current, and a low frequency current bypass circuit for preventing the detected voltage from being saturated when the detected voltage has a frequency in a low frequency band. The low frequency current bypass circuit is connected with the load resistor in parallel and has an input impedance varying with a frequency of the detected voltage. The device further includes a transimpedance amplifying circuit (inverting amplifying circuit) for transforming an impedance of the detected voltage, and a capacitor for coupling the low frequency current bypass circuit and the transimpedance amplifying circuit (inverting amplifying circuit). This makes it possible, with a relatively simple circuit and arrangement in an infrared communication receiver, to lower noises of the light receiving amplifying device while maintaining an operational range with respect to a DC photoelectric current.
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Citations
20 Claims
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1. A light receiving amplifying device, comprising:
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a light receiving device for outputting a light signal current which varies with a quantity of received light; a load resistor, connected with said light receiving device in series, for generating a detected voltage which varies with the light signal current; a low frequency current bypass circuit, being connected with said load resistor in parallel and exhibiting a high input impedance with respect to the detected voltage in a high frequency band, for preventing the detected voltage in a low frequency band from being saturated; a transimpedance amplifying circuit for transforming an impedance of the detected voltage; and a capacitor for coupling said low frequency current bypass circuit and said transimpedance amplifying circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A light receiving amplifying device including a light receiving device for generating a light signal current and a circuit for amplifying the light signal current, wherein:
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said circuit for amplifying the light signal current includes a low frequency current bypass circuit and a transimpendance amplifying circuit; and said light receiving device is connected with a load resistor in series, so that the light signal current is converted to a voltage by said load resistor and is supplied to said low frequency current bypass circuit, exhibiting a high input impedance with respect to the voltage in a high frequency band, for preventing the voltage in a low frequency band from being saturated, with an output of said low frequency current bypass circuit being supplied to said transimpedance amplifying circuit through a capacitor. - View Dependent Claims (12, 13, 14, 15)
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16. A light receiving amplifying device, comprising:
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a light receiver, adapted to receive light and output a light signal current varying in accordance with the received light; a load resistor, connected in series with the light receiver, adapted to generate a voltage varying in accordance with the light signal current; a low frequency current bypass circuit, connected in parallel with the load resistor and including a low pass filter circuit and a transconductance amplifier having a conductance, adapted to prevent the generated voltage from being saturated by varying its input impedance in accordance with a frequency of the generated voltage; a transimpendance amplifying circuit, adapted to transform an impedance of the detected voltage; and a capacitor, coupling the low frequency current bypass circuit and the transimpedance amplifying circuit. - View Dependent Claims (17, 18, 19, 20)
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Specification