## 1 Introduction  
Currently, there is a growing demand for high-voltage pulse generators, with pulses between 1 and 10 kV, with 10 s A, able to deliver high-frequency pulse bursts, in the MHz range. The generators should have high flexibility in order to apply pulses from 100 s ns to 100 s \(\upmu\)s, with capability to adjust the pulse width, polarity and amplitude from pulse-to-pulse. These different pulse shapes, including unipolar and bipolar pulses, are currently the key to the huge evolution in the application of pulsed electric fields to biological tissues for electropermeabilization of cells, in biomedical and biotechnological contexts [1]. The application of high-voltage pulses, in the range of 100 s ns to 100 s \(\upmu\)s, is very important within electroporation-based therapies and technologies in medicine and biotechnology, for example in gene electrotransfer, tissue ablation, extraction of compounds, or electrochemotherapy [2; 3; 4]. These pulses can be applied with different shapes; for example, symmetric unipolar pulses were reported [5] for biophysical tumor treatment and [6] for platelet activation and asymmetric unipolar pulses was reported [7] for tissues ablation and [8] for electroporation of mammal cells. In addition, high-frequency burst of symmetric bipolar microsecond range high-voltage pulses have been recently reported [9] to minimize the effect of muscle contractions during irreversible electroporation, Ref. [8] for electroporation of mammal cells, Ref. [10] for inducing irreversible electroporation in brain tumors and in [11] for inhibition of tumor growth. In addition, the use of bipolar asymmetric pulses was reported [12] for in vivo experimental treating of subcutaneous tumors in mice to evaluate tumor responses [13], for altering membrane permeability parameters in relation to unipolar pulse application [14], for irreversible electroporation in cardiac ablation and by [15], and for decreasing irreversible electroporation thresholds in primary and metastatic brain cancers. Finally, the application of synchronized bipolar pulses has been reported [16] to minimize neuromuscular stimulation in ablation therapies [17] for uniform tumor ablation and stimulation targeting away from electrodes, and [18] to minimize stimulation near pulse delivering electrodes in electrical stimulation. Many of these applications share the decisive advantage that the pulse width, amplitude, and polarity can be changed from pulse-to-pulse operation. While there are several techniques to generate high-voltage pulses, being the direct capacitive discharge [19], the use of transformer [20], pulse forming lines [21], and inductive energy storage [22] methods some of them. The requirement for 100 s ns to 100 s pulse variation narrows the selection to direct capacitive discharge [1]. Considering this technique and the electroporation applications in biomedical and biotechnological contexts, several authors have reported the use of semiconductor-based Marx generators, for positive and bipolar operation [8; 23; 24]. In addition, the use of a single capacitors bank with semiconductor stack has been reported [5]. Alternatively, H-bridge circuits have been used for bipolar generation individually and stacked in order to get a high amplitude voltage [5; 12; 15]. Similarly, multilevel-type generators can be used to produce bipolar pulses [15; 25]. It is worth noting that in most of the reports describing the pulse generators above, there are many details about the circuit's specifications. However, often the circuit protections are not examined, namely the overcurrent protection which is very important for circuit operation. Common to all the circuits presented is the fact that only semiconductor switches can be used, as MHz on-off capability is needed. Hence, the present demand for pulse generator technology has been driven by the evolution of solid state pulse generators, with optimized performance and reliability [26].