A new version of a very fast impulse current generator based on the use a floating electrode was designed and constructed. The "Roman generator" is an electrostatic generator able to produce lightning-like current derivatives, with amplitude in the order of kA. The design of a new prototype of the Roman generator, called here "fast impulse current generator", took in consideration the advantages of three previously built prototypes. The present prototype increases the electrostatic energy stored on the complex capacitance presented between the floating- and the earth- electrodes. The aim of the present work was to enhance the Roman generator performance by increasing its capacitance and therefore the current amplitude. In the Roman generator, an insulated metallic electrode immersed in a background electrostatic field acquires a net electrical charge different from zero, i.e. an electrostatic energy. By establishing a potential difference between the floating- and an earth- electrodes, a current impulse could bridge the interelectrodical gap distance. The obtained current impulse has a rise time in the nanoseconds range and a peak current value of some thousands of amperes. These pulses are almost constant in frequency and shape. The obtained pulses' bandwidth was close to 1 GHz, so the current and voltage measuring systems and the shielding systems were critical during the design and construction stages.