Imaging device and electronic device

Abstract

A highly sensitive imaging device that can perform imaging even under a low illuminance condition is provided. One electrode of a photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of a first transistor and one of a source electrode and a drain electrode of a third transistor. The other of the source electrode and the drain electrode of the first transistor is electrically connected to a gate electrode of the second transistor. The other electrode of the photoelectric conversion element is electrically connected to a first wiring. A gate electrode of the first transistor is electrically connected to a second wiring. When a potential supplied to the first wiring is HVDD, the highest value of a potential supplied to the second wiring is lower than HVDD.

What is claimed is: 
     
         1 . An imaging device comprising:
 a first transistor;   a second transistor;   a third transistor;   a fourth transistor; and   a photoelectric conversion element,   wherein one electrode of the photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of the first transistor,   wherein the one electrode of the photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of the third transistor,   wherein the other of the source electrode and the drain electrode of the first transistor is electrically connected to a gate electrode of the second transistor,   wherein one of a source electrode and a drain electrode of the second transistor is electrically connected to one of a source electrode and a drain electrode of the fourth transistor,   wherein the other electrode of the photoelectric conversion element is electrically connected to a first wiring,   wherein a gate electrode of the first transistor is electrically connected to a second wiring, and   wherein when a potential supplied to the first wiring is HVDD, the highest value of a potential supplied to the second wiring is lower than HVDD.   
     
     
         2 . The imaging device according to  claim 1 ,
 wherein the other of the source electrode and the drain electrode of the second transistor is electrically connected to a third wiring, and   wherein when the potential supplied to the first wiring is HVDD, a potential supplied to the third wiring is VDD, and HVDD is higher than VDD, the highest value of the potential supplied to the second wiring is VDD.   
     
     
         3 . The imaging device according to  claim 1 ,
 wherein the first transistor and the third transistor each include an oxide semiconductor in an active layer,   wherein the oxide semiconductor includes In, Zn, and M, and   wherein M is Al, Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf.   
     
     
         4 . The imaging device according to  claim 1 ,
 wherein the second transistor and the fourth transistor each include silicon in an active layer or an active region.   
     
     
         5 . An electronic device comprising:
 the imaging device according to  claim 1 ; and   a display device.   
     
     
         6 . An imaging device comprising:
 a first transistor;   a second transistor;   a third transistor;   a fourth transistor; and   a photoelectric conversion element,   wherein one electrode of the photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of the first transistor,   wherein the one electrode of the photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of the third transistor,   wherein the other of the source electrode and the drain electrode of the first transistor is electrically connected to a gate electrode of the second transistor,   wherein one of a source electrode and a drain electrode of the second transistor is electrically connected to one of a source electrode and a drain electrode of the fourth transistor,   wherein the other electrode of the photoelectric conversion element is electrically connected to a first wiring,   wherein a gate electrode of the first transistor is electrically connected to a second wiring,   wherein when a potential supplied to the first wiring is HVDD, the highest value of a potential supplied to the second wiring is lower than HVDD, and   wherein the first transistor and the third transistor are provided over the second transistor and the fourth transistor.   
     
     
         7 . The imaging device according to  claim 6 ,
 wherein the other of the source electrode and the drain electrode of the second transistor is electrically connected to a third wiring, and   wherein when the potential supplied to the first wiring is HVDD, a potential supplied to the third wiring is VDD, and HVDD is higher than VDD, the highest value of the potential supplied to the second wiring is VDD.   
     
     
         8 . The imaging device according to  claim 6 ,
 wherein the first transistor and the third transistor each include an oxide semiconductor in an active layer,   wherein the oxide semiconductor includes In, Zn, and M, and   wherein M is Al, Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf.   
     
     
         9 . The imaging device according to  claim 6 ,
 wherein the second transistor and the fourth transistor each include silicon in an active layer or an active region.   
     
     
         10 . An electronic device comprising:
 the imaging device according to  claim 6 ; and   a display device.   
     
     
         11 . An imaging device comprising:
 a first transistor;   a second transistor;   a third transistor;   a fourth transistor; and   a photoelectric conversion element,   wherein one electrode of the photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of the first transistor,   wherein the one electrode of the photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of the third transistor,   wherein the other of the source electrode and the drain electrode of the first transistor is electrically connected to a gate electrode of the second transistor,   wherein one of a source electrode and a drain electrode of the second transistor is electrically connected to one of a source electrode and a drain electrode of the fourth transistor,   wherein the other electrode of the photoelectric conversion element is electrically connected to a first wiring,   wherein a gate electrode of the first transistor is electrically connected to a second wiring,   wherein when a potential supplied to the first wiring is HVDD, the highest value of a potential supplied to the second wiring is lower than HVDD,   wherein the first transistor and the third transistor are provided over the second transistor and the fourth transistor, and   wherein the photoelectric conversion element is provided over the first transistor and the third transistor.   
     
     
         12 . The imaging device according to  claim 11 ,
 wherein the other of the source electrode and the drain electrode of the second transistor is electrically connected to a third wiring, and   wherein when the potential supplied to the first wiring is HVDD, a potential supplied to the third wiring is VDD, and HVDD is higher than VDD, the highest value of the potential supplied to the second wiring is VDD.   
     
     
         13 . The imaging device according to  claim 11 ,
 wherein the first transistor and the third transistor each include an oxide semiconductor in an active layer,   wherein the oxide semiconductor includes In, Zn, and M, and   wherein M is Al, Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf.   
     
     
         14 . The imaging device according to  claim 11 ,
 wherein the second transistor and the fourth transistor each include silicon in an active layer or an active region.   
     
     
         15 . An electronic device comprising:
 the imaging device according to  claim 11 ; and   a display device.