Flicker detection gain control circuit, digital imaging system, and method

A digital imaging system, comprising:

• a sensor array capable of capturing an image under ambient light;
• and
• a flicker detector capable of detecting flicker in the ambient light, the flicker detector comprising a gain control circuit, the gain control circuit comprising:
• a light detector capable of generating an amount of current based on received light, the light detector comprising a plurality of photodiodes;
• a first switch capable of controlling the amount of current from the light detector delivered to a node, wherein the first switch comprises a plurality of transistors;
• a charge storage element capable of providing an amount of capacitance to the node;
• a second switch capable of controlling the amount of capacitance provided to the node;
• and
• an output interface capable of delivering an output signal based on the amount of current and the amount of capacitance at the node, wherein the gain control circuit further comprises a collector coupled to the light detector via the first switch, the collector capable of collecting the amount of current from the light detector and delivering the amount of current to the node, and wherein the collector comprises a cascode transistor.

A method, comprising:

• using a plurality of photodiodes to generate an amount of current based on received light;
• controlling the amount of current delivered to a node using a plurality of first transistors, the first transistors coupling at least some of the photodiodes to a cascode transistor, the cascode transistor coupled to the node;
• providing an amount of capacitance to the node;
• controlling the amount of capacitance provided to the node;
• and
• delivering an output signal based on the amount of current and the amount of capacitance at the node.