Semiconductor optical position sensing device

• US 5,130,529 A
• Filed: 02/05/1991
• Issued: 07/14/1992
• Est. Priority Date: 02/20/1990
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Muro, Hideo
• Primary Examiner(s): Fields, Carolyn E.
• Assistant Examiner(s): Dunn, Drew A.
• Application Number:
  US07/649,836
• Time in Patent Office: 525 Days
• Field of Search: 250/214 L, 250/208.1, 250/201.2, 250/206.1, 356/223
• US Class Current: 250/214.00L
• CPC Class Codes: G01D 5/26 characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
• CPC Class Codes: H01L 31/02024 Position sensitive and lateral effect photodetectors; Quadrant photodiodes

Abstract

The semiconductor optical position sensing device comprises an optical position sensing element having two electrodes for generating two photoelectric currents changeable according to an optical position between the two electrodes, two current mirror circuits for converting the two photoelectric currents into two currents respectively; two transistors for converting the two currents into two voltages, respectively; two source followers; and a differential circuit connected between the two transistors via the two source followers, respectively, for differentially generating an optical position current signal on the basis of the two converted voltages. Further, the two source followers are composed of four parallel connected JFETs diagonally arranged close to each other in mutual intersectional positional relationship with respect to each other. Additionally, the two constant current sources are composed of four similarly-arranged JFETs. It is therefore, possible to minimize an offset error in the differential circuit. Further, since no divider is required, all the composing elements can be integrated into a single chip.

Claims

1. A semiconductor optical position sensing device, comprising:

(a) optical position sensing means having first and second electrodes for generating first and second photoelectric currents, respectively, so as to be relatively changed according to the optical position between the first and second electrodes;

(b) first current converting means connected to the first electrode of said sensing means, for converting the first photoelectric current into a first current;

(c) second current converting means connected to the second electrode of said sensing means, for converting the second photoelectric current into a second current;

(d) first logarithmic converting means connected to said first current converting means, for logarithmically converting the first current into a first voltage;

(e) second logarithmic converting means connected to said second current converting means, for logarithmically converting the second current into a second voltage;

(f) first source follower means connected to said first logarithmic converting means, for isolating said first logarithmic converting means from the succeeding stage, said first source follower means including;

(1) a pair of first parallel connected source follower field effect transistors diagonally arranged close to each other on a semiconductor substrate; and

(2) a pair of first parallel connected constant current source field effect transistors diagonally arranged close to each other on the semiconductor substrate, and connected to sources of a pair of said first parallel connected source follower field effect transistors, and

(g) second source follower means connected to said second logarithmic converting means, for isolating said second logarithmic converting means from the succeeding stage, said second source follower means including;

(1) a pair of second parallel connected source follower field effect transistors diagonally arranged close to each other in intersectional positional relationship with respect to the first source follower field effect transistors on the semiconductor substrate; and

(2) a pair of second parallel connected constant current source field effect transistors diagonally arranged close to each other in intersectional positional relationship with respect to the first constant current source field effect transistors on the semiconductor substrate, and connected to sources of a pair of said second parallel connected source follower field effect transistors, and

(h) differential means connected between said first and second logarithmic converting means via said first and second source follower means, respectively, for differentially generating an optical position current signal on the basis of the first and second voltages.

2. The semiconductor optical position sensing device of claim 1, wherein said first source follower means comprises:

(a) a pair of first parallel connected source follower field effect transistors diagonally arranged adjacent to each other on a semiconductor substrate; and

(b) ak pair of first parallel connected constant current source field effect transistors diagonally arranged adjacent to each other on the semiconductor substrate, and connected to sources of a pair of said first parallel connected source follower field effect transistors, and wherein said second source follower means comprises;

(c) a pair of second parallel connected source follower field effect transistors diagonally arranged adjacent to each other in intersectional positional relationship with respect to the first source follower field effect transistors on the semiconductor substrate; and

(d) a pair of second parallel connected constant current source field effect transistors diagonally arranged adjacent to each other in intersectional positional relationship with respect to the first constant current source field effect transistors on the semiconductor substrate, and connected to sources of a pair of said second parallel connected source follower field effect transistors.