An analog-to-digital converter includes a modulator, a controller, and a digital filter. The modulator generates a modulated signal based on an analog signal. The controller generates a weight control signal. The digital filter includes a weight signal generator and a first integrator. The weight signal generator generates a weight signal based on the weight control signal. The first integrator generates a digital signal corresponding to the analog signal by integrating the weight signal in response to the modulated signal. The weight control signal corresponds to a type and an order of the digital filter.