An image sensor , comprising: a pixel coupled to a floating diffusion region (FD); a reset select transistor coupled between the floating diffusion region and a first supply voltage (VDD); characterized in that the image sensor further comprises: an n-type source follower transistor coupled between the first supply voltage (VDD) and a second supply voltage (GND), the n-type source follower being operable to receive electrical signal from the floating diffusion region (FD); an n-type row select transistor coupled between the first supply voltage (VDD) 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 (GND), 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 ; 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 coupled to a floating diffusion region (FD); a reset select transistor coupled between the floating diffusion region and a first supply voltage (VDD); characterized in that the image sensor further comprises: an n-type source follower transistor coupled between the first supply voltage (VDD) and a second supply voltage (GND), the n-type source follower being operable to receive electrical signal from the floating diffusion region (FD); an n-type row select transistor coupled between the first supply voltage (VDD) 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 (GND), 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 ; 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 (VDD) and a second supply voltage (GND), the n-type source follower being operable to receive electrical signal from the floating diffusion region (FD); an n-type row select transistor coupled between the first supply voltage (VDD) 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 (GND), 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 ; 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 . <EOS>