Image sensor with test circuit

An image sensor comprising:

• a pixel array including a plurality of pixels;
• an analog-to-digital converter configured to use at least one counter to convert an analog signal generated from the plurality of pixels into a digital signal;
• an output buffer configured to correspond to each of a plurality of columns connected to the pixel array, and having a plurality of column memories configured to store counter test result values;
• and
• a test circuit configured to control a test operation for the at least one counter,
• wherein the output buffer receives a column selection signal and outputs a counter test result stored in a column memory corresponding to the column selection signal in response to the column selection signal, and
• the output buffer resets the column memory corresponding to the column selection signal.

An image sensor comprising:

• a plurality of pixels;
• a row decoder configured to generate a row selection signal and a pixel reset signal, and provide the row selection signal and the pixel reset signal to the plurality of pixels;
• a sampler configured to sample a reference signal and an image signal provided to a plurality of column lines that are connected to the plurality of pixels, and to output the reference signal and the image signal as a sampling signal;
• an analog-to-digital converter (ADC) configured to generate image data based on the sampling signal, and including one or more counters;
• an output buffer configured to temporarily store the image data, and output the image data;
• and
• a test circuit configured to receive a test code, and test the one or more counters based on the test code.