A sigma-delta analog-to-digital converter may include a sigma-delta modulator and a decimation filter. The sigma-delta modulator may convert a first analog input signal into a first bit stream having a first pattern using sigma-delta modulation and convert a second analog input signal into a second bit stream having a second pattern using the sigma-delta modulation. The decimation filter may integrate the number of bits having a particular value in the first bit stream, output a first digital value, calculate a bitwise complement value of the first digital value, integrate the number of bits having the particular value in the second bit stream with the bitwise complement value of the first digital value as an initial value of a second digital value, and output the second digital value.