Apparatus and a method for low noise sensing
The invention provides a method and apparatus. The apparatus includes a pixels ( 10 ) adapted to receive light and to output a current representative of the received light; a feedback circuitry ( 20 ), connected to the pixel ( 10 ), adapted to receive said current and to receive a reference current (Iref) and to provide a feedback signal to the pixel ( 10 ) at least during at least a reset stage of the pixel ( 10 ). The method includes: (i) receiving light, by a pixel 10 ), and providing a pixel output signal representative of the received light; (ii) receiving, by a feedback circuitry, the pixel output signal; and (iii) providing multiple feedback signals to the pixel at least during a reset stage of the pixel ( 10 ).
1. An apparatus comprising: a pixel adapted to receive light and to output a pixel output signal representative of the received light; and feedback circuitry, coupled to the pixel, adapted to receive said pixel output signal and to provide multiple feedback signals to the pixel at least during a reset stage of the pixel; wherein the multiple feedback signals comprise a feedback voltage signal V 0 ; wherein the pixel substantially consists of a light sensitive element, a reset transistor, an amplifying transistor and a read transistor; wherein a readout output of the pixel is arranged to receive a current Io that equals Kt*(V 0 -Vt) 2 ; wherein Kt is a gain coefficient representative of characteristics of the reset transistor; V 0 is provided to a drain of the reset transistor; and Vt is a threshold voltage of the reset transistor.
2. The apparatus of claim 1 whereas the multiple feedback signals further comprise a second feedback voltage signal.
3. The apparatus of claim 2 wherein the first feedback voltage signal affects a reset voltage provided to the pixel.
4. The apparatus of claim 2 wherein the second feedback voltage signal contributes to a reduction of a capacitance that contributes to a thermal noise of the pixel.