CMOS image sensor with noise cancellation

An image sensor, comprising:

• a photodetector;
• a reset transistor having a drain terminal coupled to reset said photodetector;
• an output transistor having a gate coupled to receive a signal from said photodetector;
• a sample circuit coupled to receive an output signal from said output transistor;
• and
• control means for switching said reset transistor into triode region so that said output transistor provides a sampled first reference output signal, for switching said reset transistor into an OFF state so that said output transistor provides a sampled reset output signal that has a voltage different from a voltage of said sampled first reference output signal and for directing said sample circuit to sample and store said sampled first reference output signal when said reset transistor is in said triode region and to sample and store said sampled reset output signal when said reset transistor is in said OFF state.

A method for generating signals from a pixel of an image sensor, the pixel having a reset transistor and an output transistor having a gate coupled to receive a signal from a photodetector, the reset transistor having a source terminal connected to receive a signal from an IN line and a drain terminal coupled to reset the photodetector, the output transistor being coupled to provide a signal to an OUT line, comprising:

• switching the reset transistor into a triode region, providing a reference signal on the IN line so that an output reference signal is provided on the OUT line;
• sampling said output reference signal while the reset transistor is in the triode region;
• switching the reset transistor to an OFF state;
• sampling a reset output signal provided on the OUT line while the reset transistor is in the OFF state, the reset output signal having a voltage different from a voltage of the output reference signal.

An image sensor, comprising:

• a photodetector;
• a reset transistor having a drain terminal coupled to reset said photodetector;
• an output transistor having a gate coupled to receive a signal from said drain terminal of said reset transistor, said output transistor configured to output a sampled first reference output signal when said reset transistor is in a triode region and a sampled reset output signal when said reset transistor is in an OFF state;
• and
• a sample circuit configured to sample and store said sampled first reference output signal when said reset transistor is in said triode region and to sample and store said sampled reset output signal when said reset transistor is in said OFF state.

An image sensor, comprising:

• a photodetector;
• a reset transistor having a drain terminal coupled to reset said photodetector;
• an output transistor having a gate coupled to receive a signal from said drain terminal of said reset transistor, said output transistor outputting a sampled first reference output signal when said reset transistor is in a triode region and a sampled reset output signal when said reset transistor is in an OFF state;
• and
• a sample circuit that samples and stores said sampled first reference output signal when said reset transistor is in said triode region and that samples and stores said sampled reset output signal when said reset transistor is in said OFF state.