Analog pre-processor with improved input common mode range

A digital imaging device comprising:

• a light sensor including an optical input and an analog electrical output;
• an analog pre-processor including an analog input and an analog output, the analog input coupled to the analog electrical output of the light sensor, the analog pre-processor including an amplifier;
• an analog-to-digital converter including an analog input and a digital output, the analog input of the analog-to-digital converter coupled to the analog output of the analog pre-processor;
• and
• a digital processing circuit including a digital input coupled to the digital output of the analog-to-digital converter,
• wherein the amplifier includes a positive input node, a negative input node, a positive output node and a negative output node, the analog pre-processor further comprising:
• a first variable capacitor coupled between the negative input node and the analog electrical output of the imaging device;
• a second variable capacitor coupled between the positive input node and a reference voltage node;
• a third variable capacitor coupled between the positive input node and the negative output node;
• a fourth variable capacitor coupled between the negative input node and the positive output node;
• a first switch coupled in series with the third variable capacitor and between the negative input node and the positive output node;
• a second switch coupled in series with the fourth variable capacitor and between the negative input node and the positive output node;
• an inverter having an output and having an input coupled to the analog electrical output of the imaging device;
• a first common mode capacitor coupled between the output of the inverter and the negative input node;
• and
• a second common mode capacitor coupled between the output of the inverter and the positive input node.