# US 10,121,815 B2 · Photo detector and associated integrated circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,121,815 B2 - Document ID: US10121815B2 - Status: Granted - Kind: B2 - Application number: 15/477,032 - Filed: 2017-04-01 - Published: 2017-10-26 - Granted: 2018-11-06 - Earliest claimed: 2016-04-21 - Assignees: Silergy Semiconductor Technology (Hangzhou) LTD - Applicants: Silergy Semiconductor Technology (Hangzhou) LTD - Inventors: Lili Shao; Huisen He; Baoyu Zhang; Yanni Zhang - Web page: https://patentgrep.com/patent/US10121815B2 ## CPC - H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors - A61B 5/0044: {for the heart} - A61B 5/02416: {using photoplethysmograph signals, e.g. generated by infrared radiation (A61B5/14552 takes precedence)} - G01J 1/16: using electric radiation detectors (G01J1/20 takes precedence) - G01J 1/44: Electric circuits {(for command of an exposure part G03B7/02)} - H10F 39/803: {Pixels having integrated switching, control, storage or amplification elements} - H10F 77/957: {for position-sensitive photodetectors, e.g. lateral-effect photodiodes or quadrant photodiodes} - G01J 2001/4247: {for testing lamps or other light sources} - G01J 2001/444: {Compensating; Calibrating, e.g. dark current, temperature drift, noise reduction or baseline correction; Adjusting} - G01J 2001/446: {Photodiode} - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - 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) ## Abstract A photo detector can include: a light emitting device configured to emit light; a driving circuit configured to drive the light emitting device; a photo-electric conversion circuit configured to generate an optical current signal according to an optical signal; an isolation circuit configured to transmit the optical current signal in an isolated manner; an ambient light filter configured to filter a current component of the optical current signal corresponding to an ambient light, and to generate a clean optical current signal; a current amplification circuit configured to amplify the clean optical current signal, and to generate an amplified optical current signal; (vii) an analog-to-digital converter configured to convert the amplified optical current signal to a digital signal; and a control circuit configured to output an optical detection signal according to the digital signal. ## Claims ### Claim 1 A photo detector, comprising: a) a light emitting device configured to emit light; b) a driving circuit configured to drive said light emitting device; c) a photo-electric conversion circuit configured to generate an optical current signal according to an optical signal; d) an isolation circuit configured to transmit said optical current signal in an isolated manner; e) an ambient light filter configured to filter a current component of said optical current signal corresponding to an ambient light, and to generate a clean optical current signal; f) a current amplification circuit configured to amplify said clean optical current signal, and to generate an amplified optical current signal; g) an analog-to-digital converter configured to convert said amplified optical current signal to a digital signal; and h) a control circuit configured to output an optical detection signal according to said digital signal. ### Claim 2 (depends on 1) The photo detector of claim 1, wherein said isolation circuit is a current mirror coupled between said photo-electric conversion circuit and said ambient light filter. ### Claim 3 (depends on 1) The photo detector of claim 1, wherein said driving circuit is configured to drive said light emitting device to emit an optical pulse according to a pulse sequence generated by said control circuit. ### Claim 4 (depends on 3) The photo detector of claim 3, wherein said ambient light filter is configured to sample a current and to obtain said current component corresponding to said ambient light in a first mode, and to filter said current component corresponding to said ambient light from said current in a second mode. ### Claim 5 (depends on 4) The photo detector of claim 4, wherein said control circuit switches said ambient light filter to said second mode at the start of an optical pulse sequence, and switches to said first mode in at least one optical pulse gap of said optical pulse sequence, and switches back to said second mode when a next optical pulse arrives. ### Claim 6 (depends on 1) The photo detector of claim 1, wherein said current amplification circuit comprises: a) a current amplifier configured to amplifier said clean optical current signal, and to generate a first amplification current signal; b) a bias circuit configured to add a bias current to said first amplification current signal, and to generate a second amplification current signal; c) a low-pass filter configured to output an average current signal according to said second amplification current signal; and d) a correction circuit configured to filter said bias current from said average current signal, and to generate said amplified optical current signal. ### Claim 7 (depends on 6) The photo detector of claim 6, wherein: a) said current amplifier comprises a programmable current amplifier; and b) said control circuit is configured to regulate an output power of said driving circuit and a gain of said programmable current amplifier according to said digital signal. ### Claim 8 (depends on 7) The photo detector of claim 7, wherein said programmable current amplifier comprises: a) a first transistor having a drain and a source coupled between a current input terminal and ground, a gate coupled to said drain; b) M current amplification branches coupled a current output terminal and ground, wherein M is a natural number greater than or equal to 2, wherein each said M current amplification branch comprises a second transistor and a control switch coupled in series, wherein gates of said first and second transistors are coupled together. ### Claim 9 (depends on 8) The photo detector of claim 8, wherein a size of said second transistor of an ith current amplification branch is (2i−1) times that of said first transistor, wherein i is a positive integer. ### Claim 10 (depends on 8) The photo detector of claim 8, wherein each of said second transistors has a same size as said first transistor. ### Claim 11 (depends on 1) The photo detector of claim 1, wherein said driving circuit, said photo-electric conversion circuit, said isolation circuit, said ambient light filter, a current amplification device, said analog-to-digital converter, and said control circuit are configured in an integrated circuit. ### Claim 12 (depends on 1) The photo detector of claim 1, configured in a heart rate detector or a distance detector.