Often a circuit requires a power supply that provides negative voltage as well as positive voltage. By reversing the direction of the diode and the capacitor (if it is polarized), the half-wave rectification circuit with low-pass filter provides a negative voltage. Similarly, reversing the direction of the diodes and capacitor in the full-wave rectified supply produces a negative voltage supply. A split power supply is shown in figure 4.9.
Figure 4.9: Split power supplies.