In this work, the theoretical and experimental study of the electric circuit is carried out for the electrostatic microgenerators based on the Bennet doubler with a power source in a variable capacitor branch. It is established that the circuit is able to operate at different capacitance modulation depth values. For the circuit with one variable capacitor, when the maximal-to-minimal capacitance ratio is less than 2, one can observe a saturation of the storage capacitor voltage (voltage autostabilization process). The equation for the saturation voltage evaluation is derived. As it is revealed for a maximal-to-minimal capacitance ratio more than 1.5, the saturation voltage is higher than power source voltage V0. When the maximal-to-minimal capacitance ratio is greater than 2, one can observe a continuous growth of the capacitor voltages as for the basic Bennet doubler conditioning circuit. A similar change of the regimes in the same circuit, but with two variable capacitors, takes place when a maximal-to-minimal capacitance ratio is about 1.618. The employment of the considered Bennet doubler conditioning circuit enables solving two main problems: operation only for a capacitance modulation depth above 2 (1.618) and the uncontrolled capacitors voltages growth. The circuit under study can be also used for electret microgenerators and for microgenerators based on using electrodes with materials having different work functions.