Analog Functions Implemented on Digital CMOS Gate Arrays---Merits and Problems

Standard digital CMOS gate arrays, originally developed for digital circuits only, also allow the implementation of analog functions on the chip. Knowing the problems and limitations, the designer can achieve a very compact solution. At first, the basic analog elements, like current mirror and difference amplifier, will be introduced. With these elements, more complex circuits can be built. Possible problems are discussed. Simulation of the circuit will demonstrate how it is an extremely useful design tool. The results of simulation and measured values are compared with a standard operational CMOS amplifier. Several industrial applications demonstrate that analog and digital functions can be combined.