Current/voltage mode image sensor with switchless active pixels

An image sensor comprising:

• a biasing circuit;
• and
• a pixel array, each pixel in the pixel array comprising a photodiode and a transfer switch transistor and sharing a reset transistor and a readout transistor with a plurality of other pixels in the pixel array,
• wherein the transfer switch transistor controls operation of the photodiode and the gate voltage of the readout transistor,
• wherein the readout transistor is configured to provide an output proportional to a voltage or current output of the photodiode, where the drains of readout transistors in the same row or column are connected directly together and to said biasing circuit or the sources of readout transistors in the same row or column are connected directly together and to said biasing circuit, wherein reference voltages or currents from said biasing circuit are applied to said readout transistor to turn on said readout transistor when an output of the photodiode is to be read out and to turn off said readout transistor when an output of the photodiode is not to be read out whereby an address transistor is not required in each pixel to turn on said readout transistor, and
• wherein the photodiode is connected between ground or a predetermined voltage and the transfer switch transistor and the transfer switch transistor is, in turn, connected to a source or drain of said reset transistor, wherein a drain or source of said reset transistor is connected to a reset voltage and said reset transistor is shared by said plurality of pixels in said pixel array.