CMOS PLL

As PLL (phase-locked loop) ICs are still somewhat expensive it seems reasonable to look around for a cheaper alternative, par- ticularly for non-critical applications that do not require such high specifications. Using two CMOS NANO gates it is possible to construct a CCO (current controlled oscillator) as described elsewhere in this issue. If a 4011 quad two-input NAND gate IC is used this leaves one gate to act as a phase comparator and another as an input amplifier.