Current Mode Image Sensor With Two Transistors per Pixel

A linear current mode active pixel sensor for low fixed-pattern noise imaging is presented. The photo pixel is composed of a photodiode, a reset transistor, and a transconductance amplifier transistor. The address switch transistor is placed outside the pixel. The increased linearity of the pixel current coupled with current mode difference double sampling greatly reduces spatial variations across the image sensor array. The fabricated image sensor is composed of an array of 50 × 128 pixels and consumes 5 mW at 30 fps. Column fixed pattern noise of 0.1% from the saturated current and signal to noise ratio of 43.3 dB is achieved.