A low power reset circuit includes a bias generator for receiving an operating voltage generated by a power supply and generating a bias voltage in response to the received operating voltage. The operation speed of a shaper for generating a shaped signal for indicating the operating voltage and the operation speed of a comparator for comparing a threshold reference voltage with the shaped signal are both controlled in response to the generated bias voltage. The comparator also generates a comparison signal for indicating a result of the comparison. In response to the comparison signal, a reset signal generator generates a reset signal for resetting protected circuitry powered by the operating voltage generated by the power supply.