# US 11,444,581 B2 · Integrated circuit and light receiver > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,444,581 B2 - Document ID: US11444581B2 - Status: Granted - Kind: B2 - Application number: 16/956,948 - Filed: 2018-03-15 - Published: 2021-01-07 - Granted: 2022-09-13 - Earliest claimed: 2018-03-15 - Assignees: Mitsubishi Electric Corporation - Applicants: Mitsubishi Electric Corporation - Inventors: Toshihide Oka - Web page: https://patentgrep.com/patent/US11444581B2 ## CPC - H03F 1/26: Modifications of amplifiers to reduce influence of noise generated by amplifying elements - H03F 3/087: {with IC amplifier blocks (H03F3/085 takes precedence)} - H03F 2200/186: the ground, reference potential being controlled - H03F 2200/372: Noise reduction and elimination in amplifier - H03F: AMPLIFIERS ## Abstract An integrated circuit includes an amplifier for amplifying an electric current signal from an external light receiving element, and a low-pass filter. The low-pass filter has a resistor and a capacitor serial-connection in which multiple capacitive elements are serially connected. With respect to the resistor in the low-pass filter, one end thereof is connected to a power terminal to which the bias voltage is inputted, and the other end thereof is connected to an input terminal of the capacitor serial-connection and to a bias application electrode of the light receiving element through which the bias voltage is applied. With respect to the capacitor serial-connection in the low-pass filter, each connection terminal between two of the serially connected capacitive elements and an output terminal of the capacitor serial-connection, are connected to their respective capacitance terminals to which a ground potential as a reference for the bias voltage is connected selectively. ## Claims ### Claim 1 An integrated circuit formed on a semiconductor substrate, for converting an electric current signal inputted from an external light receiving element, into a voltage signal, said integrated circuit comprising: an amplifier for amplifying the electric current signal from the external light receiving element and then converting it into the voltage signal; and a low-pass filter for performing filtering of a bias voltage to be applied to the external light receiving element; wherein the low-pass filter has a resistor and a capacitor serial-connection in which multiple capacitive elements are serially connected; wherein one end of the resistor is connected to a power terminal to which the bias voltage is inputted, and the other end of the resistor is connected to an input terminal of the capacitor serial-connection and to a bias application electrode of the external light receiving element through which the bias voltage is applied; wherein each connection terminal between two of the serially connected capacitive elements in the capacitor serial-connection, and an output terminal of the capacitor serial-connection, are connected to their respective capacitance terminals to which a ground potential as a reference for the bias voltage is connected selectively; and wherein the capacitance terminal is a wire bonding pad formed in the integrated circuit. ### Claim 2 (depends on 1) The integrated circuit of claim 1, wherein the capacitive element is an MIM-type capacitor. ### Claim 3 (depends on 1) A light receiver comprising: the integrated circuit of claim 1; and the external light receiving element for receiving an optical signal, wherein an electric current signal inputted from the external light receiving element is converted into a voltage signal. ### Claim 4 (depends on 3) The light receiver of claim 3, wherein, when the external light receiving element is an avalanche photodiode, the ground potential is connected to the capacitance terminal corresponding to, in the capacitor serial-connection, a portion on its side nearer to the output terminal. ### Claim 5 (depends on 3) The light receiver of claim 3, wherein, when the external light receiving element is a photodiode for which the bias voltage is lower than that for an avalanche photodiode, the ground potential is connected to the capacitance terminal corresponding to, in the capacitor serial-connection, a portion on its side nearer to the input terminal. ### Claim 6 (depends on 2) A light receiver comprising: the integrated circuit of claim 2; and the external light receiving element for receiving an optical signal, wherein an electric current signal inputted from the external light receiving element is converted into a voltage signal. ### Claim 7 An integrated circuit formed on a semiconductor substrate, for converting an electric current signal inputted from an external light receiving element, into a voltage signal, said integrated circuit comprising: an amplifier for amplifying the electric current signal from the external light receiving element and then converting it into the voltage signal; and a low-pass filter for performing filtering of a bias voltage to be applied to the external light receiving element; wherein the low-pass filter has a resistor and a capacitor serial-connection in which multiple capacitive elements are serially connected; wherein one end of the resistor is connected to a power terminal to which the bias voltage is inputted, and the other end of the resistor is connected to an input terminal of the capacitor serial-connection and to a bias application electrode of the external light receiving element through which the bias voltage is applied; and wherein each connection terminal between two of the serially connected capacitive elements in the capacitor serial-connection is connected to a capacitance terminal to which a ground potential as a reference for the bias voltage is connected selectively, and an output terminal of the capacitor serial-connection is fixed at the ground potential, and the capacitance terminal is a wire bonding pad formed in the integrated circuit. ### Claim 8 (depends on 7) A light receiver comprising: the integrated circuit of claim 7; and the external light receiving element for receiving an optical signal; wherein an electric current signal inputted from the external light receiving element is converted into a voltage signal, and; wherein, when the external light receiving element is an avalanche photodiode, the ground potential is not connected to any of the capacitance terminals. ### Claim 9 (depends on 7) The integrated circuit of claim 7, wherein the capacitive element is an MIM-type capacitor. ### Claim 10 (depends on 7) A light receiver comprising: the integrated circuit of claim 7; and the external light receiving element for receiving an optical signal, wherein an electric current signal inputted from the external light receiving element is converted into a voltage signal.