# US 9,520,844 B2 · Electromagnetic radiation detection circuit for pulse detection including an amplifying transistor and a coupling capacitor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,844 B2 - Document ID: US9520844B2 - Status: Granted - Kind: B2 - Application number: 14/362,761 - Filed: 2012-12-10 - Published: 2014-11-20 - Granted: 2016-12-13 - Earliest claimed: 2011-12-08 - Assignees: Societe Francaise de Detecteurs Infrarouges-Sofradir - Applicants: Societe Francaise De Detecteurs Infrarouges-Sofradir - Inventors: Eric Sanson - Web page: https://patentgrep.com/patent/US9520844B2 ## CPC - H03F 3/087: {with IC amplifier blocks (H03F3/085 takes precedence)} - G01J 1/46: using a capacitor - H04N 23/20: for generating image signals from infrared radiation only - H10F 39/103: {the at least one element covered by H10F30/00 having potential barriers, e.g. integrated devices comprising photodiodes or phototransistors} - G01S 3/784: using a mosaic of detectors - H03F: AMPLIFIERS - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract An electromagnetic radiation detection circuit includes a photodetector transforming the received electromagnetic radiation into an electric current. A bias circuit is connected to the photodetector. An amplifying circuit has an input terminal coupled to the photodetector. An amplifying transistor has a first low-impedance electrode forming the input terminal of the amplifying circuit and a second low-impedance electrode coupled to an output terminal of the detection circuit. The transistor is configured to conduct the current applied on the first electrode. A high-impedance electric load is connected to the second electrode to deliver a voltage representative of the electric current originating from the photodetector. ## Claims ### Claim 1 An electromagnetic radiation detection circuit comprising: a photodetector configured to transform the received electromagnetic radiation into an electric current: a bias circuit connected to terminals of the photodetector, the bias circuit receiving a first part of a current emitted by the photodetector; an amplifying circuit, which is different from the bias circuit, and comprising an amplifying transistor formed by a field-effect transistor or a bipolar transistor, the field-effect transistor or the bipolar transistor having a first electrode forming an input terminal of the amplifying circuit coupled to a first terminal of the photo-detector so as to receive a second part of the electric current emitted by the photodetector, the first electrode being a source electrode or an emitter electrode, the field-effect transistor or the bipolar transistor having a second electrode coupled to an output terminal of the electromagnetic radiation detection circuit, the second electrode being a drain electrode or a collector electrode, and the amplifying circuit being configured so that the electric current applied to the first electrode flows through the amplifying transistor and so as to provide this electric current on the output terminal with an impedance higher than an impedance on the first electrode; a voltage source connected to a control electrode of the amplifying transistor; and a passive electric load connected to the second electrode of the amplifying transistor, wherein a first terminal of a coupling capacitor is directly connected to the first terminal of the photodetector and to the bias circuit, and a second terminal of the coupling capacitor is directly connected to the first electrode of the amplifying transistor. ### Claim 2 (depends on 1) The circuit according to claim 1, wherein the passive electric load is a diode. ### Claim 3 (depends on 1) The circuit according to claim 1, comprising a current source configured to be in a saturated state in an idle state, said current source being connected to the second electrode of the amplifying transistor. ### Claim 4 (depends on 2) The circuit according to claim 2, wherein the diode is assembled between a current source and the output terminal. ### Claim 5 (depends on 2) The circuit according to claim 2, wherein the bias circuit comprises an additional diode-connected transistor connected between a bias line and the first terminal of the photodetector. ### Claim 6 (depends on 1) The circuit according to claim 1, wherein a passive load comprising an additional diode-connected transistor is connected between a bias line and the first electrode of the amplifying circuit, and is configured to form a saturated current source. ### Claim 7 (depends on 1) The circuit according to claim 1, wherein the voltage source connected to the control electrode of the amplifying transistor is configured to define an intensity of a current flowing through the amplifying transistor in an idle phase. ### Claim 8 (depends on 1) The circuit according to claim 1, wherein the passive load comprising an additional diode-connected transistor is connected between a bias line and the first electrode of the amplifying circuit and configured to define a threshold value of a current pulse detected by the amplifying circuit. ### Claim 9 (depends on 1) The circuit according to claim 1, wherein the passive load comprising an additional diode-connected transistor is connected between a bias line and the first electrode of the amplifying circuit and configured to deliver a binary signal to the output terminal. ### Claim 10 (depends on 5) The circuit according to claim 5, wherein the additional diode-connected transistor is a metal-oxide-semiconductor (MOS) transistor of a first type and the amplifying transistor is a MOS transistor of a second type opposite to the first type so as to increase transfer of a current pulse provided by the photodetector. ### Claim 11 (depends on 1) The circuit according to claim 1, wherein the bias circuit and the amplifying circuit are configured so that a pulsed portion of a signal emitted by the photodetector mainly reaches the amplifying circuit and a static portion of the signal emitted by the photodetector mainly reaches the bias circuit. ### Claim 12 (depends on 1) The circuit according to claim 1, wherein the bias circuit is configured to substantially not absorb a pulsed signal provided by the photodetector. ### Claim 13 (depends on 1) The circuit according to claim 1, wherein the amplifying circuit has a low impedance in a high-frequency range and a high impedance in a low-frequency range. ### Claim 14 (depends on 1) The circuit according to claim 1, wherein in a high frequency range, an input impedance of amplifying circuit is lower than an input impedance of the bias circuit. ### Claim 15 (depends on 1) The circuit according to claim 1, wherein, the amplifying transistor, the bias circuit and the photodetector are configured so that a current flowing through amplifying transistor is directed in a same direction as a current from the bias circuit for the biasing of photodetector. ### Claim 16 An electromagnetic radiation detection circuit comprising: a photodetector configured to transform the received electromagnetic radiation into an electric current; a bias circuit connected to terminals of the photodetector, the bias circuit receiving a first part of a current emitted by the photodetector; an amplifying circuit, which is different from the bias circuit, and comprising an amplifying transistor formed by a field-effect transistor or a bipolar transistor, the field-effect transistor or the bipolar transistor having a first electrode forming an input terminal of the amplifying circuit coupled to a first terminal of the photo-detector so as to receive a second part of the electric current emitted by the photodetector, the first electrode being a source electrode or an emitter electrode, the field-effect transistor or the bipolar transistor having a second electrode coupled to an output terminal of the electromagnetic radiation detection circuit, the second electrode being a drain electrode or a collector electrode, and the amplifying circuit being configured so that the electric current applied to the first electrode flows through the amplifying transistor and so as to provide this electric current on the output terminal with an impedance higher than an impedance on the first electrode; a voltage source connected to a control electrode of the amplifying transistor; and a passive electric load connected to the second electrode of the amplifying transistor, wherein the source terminal or the emitter terminal of the amplifying circuit is connected to a terminal of the photodetector by means of a coupling circuit configured to allow only a part of the signal emitted by the photodetector to pass through the coupling circuit. ### Claim 17 (depends on 16) The circuit according to claim 16, wherein the coupling circuit has a first terminal connected to an electric node common to the photodetector and to the bias circuit. ### Claim 18 (depends on 17) The circuit according to claim 17, wherein the coupling circuit has a second terminal connected to the first electrode of the amplifying transistor. ### Claim 19 (depends on 18) The circuit according to claim 18, wherein the coupling circuit includes a coupling capacitor having a first terminal connected to the electric node common to the photodetector and to the bias circuit and a second terminal connected to the first electrode of the amplifying transistor.