Invention Grant
- Patent Title: Photocurrent sensing circuit converting an illumination of visible light into an electric signal as well as photosensor and electronic device with the photocurrent sensing circuit
- Patent Title (中): 光电流检测电路将可见光的照明转换成电信号,以及光电传感器和电子器件与光电流检测电路
-
Application No.: US11907597Application Date: 2007-10-15
-
Publication No.: US07683955B2Publication Date: 2010-03-23
- Inventor: Takayuki Shimizu
- Applicant: Takayuki Shimizu
- Applicant Address: JP Osaka
- Assignee: Sharp Kabushiki Kaisha
- Current Assignee: Sharp Kabushiki Kaisha
- Current Assignee Address: JP Osaka
- Agency: Birch, Stewart, Kolasch & Birch LLP
- Priority: JP2006-303062 20061108
- Main IPC: H04N3/14
- IPC: H04N3/14

Abstract:
A photocurrent sensing circuit includes a logarithmic compression circuit; a cancellation circuit logarithmically compressing a current substantially equal in temperature coefficient of the photocurrent to convert the same into a voltage, and performing an addition or a subtraction on the converted voltage and a voltage converted from a photocurrent by logarithmically compression; a logarithmic operation circuit logarithmically compressing the voltage received from the cancellation circuit to produce a first voltage, logarithmically compressing a voltage proportional to a thermal voltage of the photocurrent to produce a second voltage, logarithmically compressing a current having thermal dependence of nearly zero to produce a third voltage and performing an addition or a subtraction of each of the second and third voltages with respect to the first voltage to produce a fourth voltage; and an inverse logarithmic transformation circuit performing inverse logarithmic transformation on the fourth voltage to output a current.
Public/Granted literature
Information query