Figure 1 shows a block diagram of the 4046, which has been implemented on a single monolithic integrated circuit. The PLL structure consists of a low-power, linear VCO and two different phase comparators, having a common signal-input amplifier and a common comparator input. A 5.2-V Zener diode is provided for supply regulation, if necessary. The VCO can be connected either directly or through frequency dividers to the comparator input of the phase comparators. The LPF is implemented through external parts because of the radical configuration changes from application to application and because some of the components cannot be integrated. The 4046 is available in 16-lead ceramic dual-in-line packages (D and F suffixes), 16-lead dual-in-line plastic packages (E suffix), 16-lead small outline package (NSR suffix) and in chip form (H suffix).