**4.2 Power supply**

Basically, agarose gel electrophoresis is achieved in around 100 volts [19]. In laboratories of molecular biology and biochemistry, power supply for SDS-PAGE is very popular equipment. This supply gives fine and direct current, promising proteins to migrate correctly. Of course, this power supply is also available for use in agarose gel electrophoresis. But actually, such a high-quality direct current is not needed in agarose gel electrophoresis.

Generally, the household electric power is supplied as alternating current (**Figure 11(a)**). This alternating current is not usable as electrophoresis. The current is passed through a diode, and an odd part of the current is picked up (half-wave rectification (**Figure 11(b)**)). A combination of diode enables to make all the alternating current as one direction (full-wave rectification (**Figure 11(c)**)). Half-wave rectified current and full-wave rectified current are a kind of pulsating current, which is not a true direct current (**Figure 11(d)**). It is known that such halfwave or full-wave rectified current is enough for agarose gel electrophoresis [20].
