Multi-beta pixel circuit and image sensor circuit using same

Patent metadata

Field	Value
Publication number	US-2021368113-A1
Application number	US-202016879655-A
Country	US
Kind code	A1
Filing date	May 20, 2020
Priority date	May 20, 2020
Publication date	Nov 25, 2021
Grant date	—

Abstract

An image sensor uses a pixel circuit which includes a BJT phototransistor having multiple selectable beta values. The BJT is one semiconductor device includes: a substrate having a first conductivity type; a first well having the first conductivity type; a collector electrode having the first conductivity type in the first well; a second well having a first concentration of a second conductivity type; a first emitter electrode having the first conductivity type in the second well; a base electrode having the second conductivity type in the second well; a third well having a second concentration of the second conductivity type, wherein the second concentration is different from the first concentration; and a second emitter electrode having the first conductivity type in the third well.

First claim

What is claimed is:

1 . A pixel circuit for use in an image sensor, comprising:
a bipolar junction transistor (BJT) having a base, a collector, and a plurality of emitters, wherein the BJT is a phototransistor whose current generates a pixel signal for the pixel circuit; a shutter control stage configured to operably control an exposure of the BJT; a readout stage configured to operably read out the pixel signal; and one or more switches configured to respectively control corresponding one or more of the plurality of emitters; whereby the BJT has multiple selectable beta values by controlling the one or more switches.

2 . The pixel circuit of claim 1 , further including a storage device for storing the pixel signal.

3 . The pixel circuit of claim 1 , wherein a total number of the switches corresponds to a total number of the emitters.

4 . The pixel circuit of claim 1 , wherein a total number of the switches corresponds to a total number of the emitters minus one.

5 . The pixel circuit of claim 1 , wherein the BJT is one semiconductor device including:
a substrate having a first conductivity type; a first well having the first conductivity type; a collector electrode having the first conductivity type in the first well; a second well having a first concentration of a second conductivity type; a first emitter electrode having the first conductivity type in the second well; a base electrode having the second conductivity type in the second well; a third well having a second concentration of the second conductivity type, wherein the second concentration is different from the first concentration; and a second emitter electrode having the first conductivity type in the third well.

6 . An image sensor, comprising:
a plurality of pixel circuits configured to operably sense an intensity of light to generate pixel signals; and column and row selectors to select the pixel circuits to output the pixel signals as an image output signal; wherein each of the pixel circuits includes: a bipolar junction transistor (BJT) having a base, a collector, and a plurality of emitters, wherein the BJT is a phototransistor whose current generates the pixel signal for the corresponding pixel circuit; a shutter control stage configured to operably control an exposure of the BJT; a readout stage configured to operably read out the pixel signal; and one or more switches configured to respectively control corresponding one or more of the plurality of emitters; whereby the BJT has multiple selectable beta values by controlling the one or more switches.

7 . The image sensor of claim 6 , wherein each of the pixel circuits further includes a storage device for storing the pixel signal.

8 . The image sensor of claim 6 , wherein a total number of the switches corresponds to a total number of the emitters.

9 . The image sensor of claim 6 , wherein a total number of the switches corresponds to a total number of the emitters minus one.

10 . The image sensor of claim 6 , wherein the BJT is one semiconductor device including:
a substrate having a first conductivity type; a first well having the first conductivity type; a collector electrode having the first conductivity type in the first well; a second well having a first concentration of a second conductivity type; a first emitter electrode having the first conductivity type in the second well; a base electrode having the second conductivity type in the second well; a third well having a second concentration of the second conductivity type, wherein the second concentration is different from the first concentration; and a second emitter electrode having the first conductivity type in the third well.

Assignees

• Pixart Imaging Inc

Inventors

• Lim Wooi-Kip
• Tan Shan-Chong

Classifications

• H04N25/57 Primary

  Control of the dynamic range · CPC title

• H04N25/70 Primary

  SSIS architectures; Circuits associated therewith · CPC title

• H04N25/77

  Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components · CPC title

• H10F39/197 Primary

  Bipolar transistor image sensors · CPC title

• H04N25/76

  Addressed sensors, e.g. MOS or CMOS sensors · CPC title