System and method of DC calibration of amplifiers

A method of transparently calibrating at least one amplifier of an array of amplifiers during operation of a circuit employing the amplifier array, each amplifier having a compensation input, said method comprising:

• providing a pair of redundant amplifiers on either side of the amplifier array;
• providing an interpolative resistive ladder across the outputs of the amplifier array and outputs of the redundant amplifiers;
• removing inputs and outputs of an amplifier of the amplifier array from the circuit;
• shorting the inputs of the removed amplifier to a common mode voltage;
• measuring an output offset of the removed amplifier;
• adjusting a corresponding compensation bias applied at the compensation input of the removed amplifier in an attempt to reduce the measured output offset;
• and
• re-connecting the inputs and outputs of the amplifier to the circuit.

A compensation system for calibrating an amplifier having a compensation input, the compensation system comprising:

• a sigma delta converter that converts an offset voltage to a bit stream indicative of the offset voltage;
• a counter, coupled to receive the bit stream from the sigma delta converter, that stores a sum value indicative of the output offset;
• a memory that stores a digital bias value;
• adjust logic, coupled to the counter and the memory, that determines an adjust value based on the sum value and that is configured to adjust the stored digital bias value based on the adjust value;
• a digital to analog converter (DAC), coupled to the memory, that converts the digital bias value to a differential bias current;
• a pair of compensation capacitors that collectively apply a differential compensation voltage to a differential input of the amplifier;
• and
• a pair of current to voltage converters, coupled to the DAC and to the pair of compensation capacitors of the amplifier, that charges the pair of compensation capacitors using the differential bias current.