1.  Field of the Invention
The present invention relates to analog-to-digital converters, and in particular relates to circuit mismatch problems of analog-to-digital converters using delta-sigma modulation. 
2.  Description of the Related Art
Delta-sigma modulation is generally used in analog-to-digital converters.  The differential pair architecture of the delta-sigma modulation design helps to suppress power supply noise and reduce circuit nonlinearity. 
In the differential pair architecture, a matching circuit design is especially important.  The way to cope with circuit mismatch problems of the differential pair architecture is an important issue in the circuit design field.