The search for compact autonomous devices has been increasing in the microelectronics industry. These devices have the capacity to generate their own energy in order to be charged. One of the ways of harvesting environmental energy for charging such devices is by using mechanical vibrations through the use of variable capacitor. Taking this principle into account, this work presents a behavioral analysis of a system model of harvesting vibratory energy for low power, made up of a circuit which includes a variable capacitor. An architecture of a circuit which improves the relation concerning the amount of harvested energy/circuit area in relation to conventional architectures is also presented as well as a comparison between the circuit with the proposed architecture and the conventional circuit. In this way, it was verified that, under the same functioning conditions, the conventional circuit harvested a maximum power of 4,5 μW whereas the circuit with the new architecture harvested a 6,25 μW power.