An image sensor (100, 200, 300), comprising: a pixel (101, 201, 301) coupled to a floating diffusion region; a reset select transistor coupled between the floating diffusion region and a first supply voltage; characterized in that the image sensor (100, 200, 300) further comprises: an n-type source follower transistor coupled between the first supply voltage and a second supply voltage, the n-type source follower being operable to receive electrical signal from the floating diffusion region; an n-type row select transistor coupled between the first supply voltage and the n-type source follower transistor, wherein a drain of the reset select transistor is directly connected to a drain of the n-type row select transistor; a first sample-and-hold capacitor coupled between a third supply voltage (VRST) and the second supply voltage, wherein a capacitance of the first sample-and-hold capacitor is adjustable and is configured according to a light level of incident light of the pixel (101, 201, 301); a first switch coupled between the n-type row select transistor and the first sample-and-hold capacitor; and a second switch coupled between the third supply voltage (VRST) and the first sample-and-hold capacitor. a pixel (101, 201, 301) coupled to a floating diffusion region; a reset select transistor coupled between the floating diffusion region and a first supply voltage; characterized in that the image sensor (100, 200, 300) further comprises: an n-type source follower transistor coupled between the first supply voltage and a second supply voltage, the n-type source follower being operable to receive electrical signal from the floating diffusion region; an n-type row select transistor coupled between the first supply voltage and the n-type source follower transistor, wherein a drain of the reset select transistor is directly connected to a drain of the n-type row select transistor; a first sample-and-hold capacitor coupled between a third supply voltage (VRST) and the second supply voltage, wherein a capacitance of the first sample-and-hold capacitor is adjustable and is configured according to a light level of incident light of the pixel (101, 201, 301); a first switch coupled between the n-type row select transistor and the first sample-and-hold capacitor; and a second switch coupled between the third supply voltage (VRST) and the first sample-and-hold capacitor. an n-type source follower transistor coupled between the first supply voltage and a second supply voltage, the n-type source follower being operable to receive electrical signal from the floating diffusion region; an n-type row select transistor coupled between the first supply voltage and the n-type source follower transistor, wherein a drain of the reset select transistor is directly connected to a drain of the n-type row select transistor; a first sample-and-hold capacitor coupled between a third supply voltage (VRST) and the second supply voltage, wherein a capacitance of the first sample-and-hold capacitor is adjustable and is configured according to a light level of incident light of the pixel (101, 201, 301); a first switch coupled between the n-type row select transistor and the first sample-and-hold capacitor; and a second switch coupled between the third supply voltage (VRST) and the first sample-and-hold capacitor.