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We are interested in the amplification of very low voltages produced by solar cells during sunset or weak sunshine. The study uses a device consisting of a Duffing oscillator, which amplifies and automatically regulates a low-voltage input, an inverter that reverses the negative voltage of one of the outputs of the oscillator, and a summing device to add the voltages of the two oscillator outputs. Experimental and theoretical investigations are conducted, and it is observed from the results that the output voltage can reach to 7.03V for an input voltage of 0.43V, i.e. a gain of 24.3dB. Furthermore, we observe from the amplification factor, and the behavior of the cyclic ratio that the whole system nonlinearly amplifies the input voltage with a large factor for weak inputs. We finally compare the results produced by the proposed system and those produced by a conventional boost converter at very low voltages. It then results that the Duffing oscillator provides large amplification factors for low voltages.