Patent ID: 8330631

Claim:
A method for calibrating a fixed gain amplifier configured as a front-end amplification stage of an analog-to-digital converter, 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 at the fixed gain amplifier; sampling the calibration voltage to generate a first input sample at a first sampling interval with the fixed gain amplifier bypassed; reversing the polarity of the calibration voltage; sampling the inversed polarity calibration voltage to generate a second input sample at a second sampling interval with the fixed gain amplifier bypassed; generating a first offset corrected digital output code being half of the difference of the digital output codes associated with the first and second input samples; sampling the calibration voltage to generate a third input sample at a third sampling interval through the fixed gain amplifier; reversing the polarity of the calibration voltage; sampling the inversed polarity calibration voltage to generate a fourth input sample at a fourth sampling interval through the fixed gain amplifier; generating a second offset corrected digital output code being half of the difference of the digital output codes associated with the third and fourth input samples; computing an actual gain value of the fixed gain amplifier from the ratio of the second offset corrected digital output code to the first offset corrected digital output code; and generating a gain correction value for the fixed gain amplifier being the ratio of an ideal gain to the actual gain value of the fixed gain amplifier.