A p–n–p–n diode consists of four layers of silicon and these layers are doped alternately with p- and n-type impurities, as shown in Fig. 16.23(a). This can be redrawn as shown in Fig. 16.23(b). The p–n–p–n diode is represented schematically as shown in Fig. 16.23(c).
FIGURE 16.23(a) A p–n–p–n diode
FIGURE 16.23(b) The redrawn circuit of Fig. 16.23(a)
FIGURE 16.23(c) The schematic representation of p–n–p–n