Background calibration method for fixed gain amplifiers

A method for calibrating an analog-to-digital converter including a fixed gain amplifier configured as a front-end amplification stage and a modulator, the analog-to-digital converter receiving an analog input signal and generating digital output codes indicative of the analog input signal, the method comprising:

• generating an offset correction value and a modulator gain correction value;
• wherein generating the offset correction value comprises:
• sampling the analog input signal at a plurality of sampling intervals at an input of the fixed gain amplifier to generate an input sample for each sampling interval;
• reversing the polarity of at least one input sample;
• generating digital output codes indicative of the input samples at an output of the modulator;
• averaging the digital output codes associated with a first pair of input samples, the first pair of input samples having opposite polarities;
• generating the offset correction value being the average of the digital output codes associated with the first pair of input samples, the offset correction value correcting for at least offset errors in the fixed gain amplifier and in the modulator;
• and wherein generating the modulator gain correction value comprises:
• calibrating the modulator using a plurality of input samples including input samples with unmodified magnitude and input samples with modified magnitude;
• and
• computing an actual gain value of the modulator using the digital output codes associated with an input sample with unmodified magnitude and another input sample with modified magnitude;
• and
• generating the modulator gain correction value being the ratio of an ideal gain of the modulator to the actual gain of the modulator.

A method for calibrating an analog-to-digital converter including a fixed gain amplifier configured as a front-end amplification stage and a modulator, the analog-to digital converter receiving an analog input signal and generating digital output codes indicative of the analog input signal, the method comprising:

• generating a calibration voltage;
• sampling the calibration voltage at a plurality of sampling intervals at an input of the fixed gain amplifier to generate an input sample for each sampling interval;
• reversing the polarity of at least one input sample;
• generating digital output codes indicative of the input samples at an output of the modulator;
• averaging the digital output codes associated with a first pair of input samples, the first pair of input samples having opposite polarities;
• and
• generating an offset correction value being the average of the digital output codes associated with the first pair of input samples, the offset correction value correcting for at least offset errors in the fixed gain amplifier and in the modulator.