Apparatus and methods for analog-to-digital converters are provided. In an example, a sigma-delta analog-to-digital converter (ADC) can include a modulator configured to receive an analog signal and a decimation filter configured to provide a digital representation of the analog signal using an output of the modulator. In certain examples, the modulator can includes an integrator and a comparator od quantizer coupled to an output of the integrator. The comparator, in certain examples, can be configured to receive a second signal from the output of the integrator and to receive a plurality of dither signals, the dither signals can be configured to prevent limit cycles of the sigma-delta ADC.