This invention provides a relaxation oscillator, including a first comparator, a second comparator, an SR latch, and a capacitor control module. Input ends of the two comparators are coupled with the capacitor control module and an external reference threshold voltage, and two output ends are coupled with the input ends of the SR latch; output ends of the SR latch are coupled with input ends of the capacitor control module; According to the external reference threshold voltage, a first comparison signal generated by the first comparator and a second comparison signal generated by the second comparator are inputted into the SR latch to generate a control signal. According to a bias current of the external bias current source and the control signal outputted by the SR latch, periodic charging and discharging of a first capacitor and a second capacitor are controlled to generate oscillating signals.
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