A small, low-power bootstrapped boost regulator is introduced that can start up with an input voltage of 240 mV and achieve a maximum efficiency of 97%. The proposed circuit uses two separate control schemes for start-up and steady-state operation. A fixed-frequency oscillator is used to initially start up the circuit and raise the output voltage. Once the output voltage has reached a level adequate to bias the internal circuitry, a constant-on-time-style hysteretic control scheme is used, which helps increase system efficiency compared to using a conventional pulse-width-modulated control scheme. While maintaining high efficiency, the proposed circuit only requires three external components: two capacitors (input and output) and an inductor. The effectiveness of this approach is shown through Spectre® simulation results.