Image sensor and operation method of pixel circuit thereof

An operation method of a pixel circuit, comprising:

• selectively operating the pixel circuit in one of a low illumination sensing mode and a high illumination sensing mode, wherein a first transfer transistor of the pixel circuit is coupled between a first photosensitive element of the pixel circuit and a floating diffusion portion of the pixel circuit, a source follower circuit of the pixel circuit is coupled between a corresponding readout line of the pixel circuit and the floating diffusion portion, a first terminal of a dual floating diffusion transistor of the pixel circuit is coupled to the floating diffusion portion, and a first terminal of a first capacitor of the pixel circuit is coupled to a second terminal of the dual floating diffusion transistor;
• performing a precharge operation on the pixel circuit to reset the first photosensitive element, the floating diffusion portion, and the first capacitor;
• in response to the pixel circuit operating in the low illumination sensing mode, applying a control voltage with a first level to a control terminal of the first transfer transistor during an integration period after the precharge operation to turn off the first transfer transistor;
• and
• in response to the pixel circuit operating in the high illumination sensing mode, applying the control voltage with a second level higher than the first level to the control terminal of the first transfer transistor during the integration period to turn off the first transfer transistor.