Techniques are described for error-modulated pixel readout by column-parallel programmable gain amplifiers (PGAs) in a digital image sensor. Each PGA has an amplifier with gain set by a ratio of input and feedback capacitors. Mismatch between these capacitors can manifest as vertical fixed pattern noise (FPN) in the image output. Embodiments use a swap control signal to pseudo-randomly toggle between two or more swap states for each of a sequence of row scan times. Each swap state at least directs coupling of a particular capacitor network in either the input or the feedback path of the amplifier. Pseudo-randomly swapping those couplings of the capacitive networks also pseudo-randomly modulates gain error from capacitive mismatch between the capacitor networks. The FPN effectively becomes spatially modulated noise at a level far below what would be considered as a visible artifact in the image output.
REDUCTION OF FIXED-PATTERN NOISE IN DIGITAL IMAGE SENSORS BY MITIGATING GAIN MISMATCH ERROR