This brief presents an analog multiplier based controller for a noninverting buck-boost (NIBB) converter, in which the controller can work for both buck and boost modes of the NIBB converter, thus simplifying the design and saving the power and area for the controller. Moreover, it can obtain good line regulation and load regulation performances. The analog multiplier based controller can automatically change over between the buck and boost modes according to the input and output voltages. This work, fabricated in 65-nm CMOS process, exhibits a core area of 1.67 × 0.64mm2 It outputs a stable 0.9 V when the input voltage changes from 0.7-1.4 V, with a maximum output load current of 200 mA.