## 3 Overview  
### Advantages and Disadvantages of the Typical Electroporator Concepts  
The presented concepts of pulse generators demonstrate the diversity of techniques used for high-voltage pulse generation suitable for electroporation applications. All the techniques are summarized in the Figure 13.  
Figure 11: The circuit of a diode opening switch generator. Figure 12: The conceptual circuit of a transformers-based pulse generator. Based on the energy storage, the pulse generators can be divided into three main groups: direct capacitor discharge, transmission line discharge and inductive storage discharge. Each has advantages and disadvantages, which are summarized in the Table 1.  
Further, the in-house built nsPEF generators were analyzed and classified based on the switching type. The review focused only on nsPEF pulse generators, which were reported specifically for the application in the field of electroporation. We have included only the references where the reported duration of the pulse is in the sub-microsecond range (below 1 \(\upmu\)s). In total 63 nsPEF generators for electroporation matched the requirements and are listed in Table 2. The devices are grouped based on the pulse forming circuit with the following parameters reported: pulse form, pulse duration, maximum pulse amplitude, pulse repetition frequency, switch type, switch model and additional remarks on the pulse form and topology in case the divergence from the usual performance is noticed. Figure 13: The diversity of pulse generators topologies for electroporation applications. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Concept** & & **Advantage** & **Disadvantage** \\ \hline \multirow{8}{*}{Direct Capacizer} & \multirow{8}{*}{**Unipolar**} & \multirow{8}{*}{**Bipolar**} & Simple and inexpensive construction for systems up to 1 kV: \\  & & Very flexible pulse shape control in the & High opacity opacity obtains are required for rectangular \\  & & sub-microscopic— millisecond range: \\  & & Can operate in a high frequency range. & wave delivery into high loads \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\ \hline \multirow{8}{*}{Transmission line} & \multirow{8}{*}{**Bianlein**} & Simple design, & \multirow{8}{*}{Lapsed under machine requirements} \\  & & Commonly used for short pulse generation (sub-100 ns), & & \\  & & High-volongs and currents: & & \\  & & Can be used for bipolar pulses & & \\  & & & \\  & & & \\  & & & \\  & & & & \\  & & & \\ \hline \multirow{8}{*}{Inductive Storage} & \multirow{8}{*}{**Disolate Opening Switch**} & High energy density: & \multirow{8}{*}{Lapsed under machine requirements} \\  & & Accessible electrical components: & Low output power: \\  & & Variable load impedance: & & \\  & & Commonly used for short pulse generation (sub-100 ns), & Complex control system: \\  & & Fast repetition frequency: & & \\ \hline \multirow{8}{*}{**Transformer based**} & \multirow{8}{*}{**Transformer based**} & High pulse amplitude: & \multirow{8}{*}{Lapsed under machine requirements} \\  & & Applicable with low voltage switches; & & \\  & & Flexible pulse amplitude. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The comparison between the topologies of pulse generators used for electroporation.