Image sensor with analog sample and hold circuit control for analog neural networks

A system comprising:

• a cross-point synapse array comprising:
• a plurality of row wires;
• a plurality of column wires;
• a plurality of cross-point devices, a cross-point device at each intersection of the row wires and the column wires stores a weight value;
• and
• a plurality of pixel unit circuits, each pixel unit circuit is coupled with a predetermined set of cross-point devices, wherein the pixel unit circuit generates a voltage output based on an input light, the voltage output being sent to the set of cross-point devices for conversion to corresponding current signals, wherein the cross-point synapse array converts the voltage output of each pixel unit circuit to a corresponding current value using the weight value stored at each cross-point device;
• and
• a pixel unit controller coupled with the cross-point synapse array, the pixel unit controller adjusts an exposure time of the pixel unit circuits based on a plurality of voltage outputs from the plurality of pixel unit circuits respectively.

A computer-implemented method for operating a neural network system, the computer-implemented method comprising:

• receiving, by a plurality of pixel unit circuits in an image sensor array, a reset signal from a pixel unit controller, each pixel unit circuit is connected to a corresponding row wire of a cross-point synapse array, the cross-point synapse array comprising a plurality of row wires, a plurality of column wires, and a plurality of cross-point devices, wherein a cross-point device at each intersection of the row wires and the column wires stores a weight value;
• receiving, by the plurality of pixel unit circuits in the image sensor array, a sample-and-hold signal from the pixel unit controller, each pixel unit circuit generating a voltage output based on an input light for an exposure time duration of a sample phase of the sample-and-hold signal;
• sending the voltage output from the plurality of pixel unit circuits in the image sensor array to corresponding cross-point devices in a cross-point synapse array for conversion to corresponding current signals during a hold phase of the sample-and-hold signal, wherein the cross-point synapse array converts the voltage output of each pixel unit circuit to a current value using the weight value stored at each cross-point device;
• and
• adjusting, by the pixel unit controller, the exposure time of the pixel unit circuits based on the voltage outputs from the plurality of pixel unit circuits respectively.