A CMOS cubic voltage generator for a temperature compensated crystal oscillator (TCXO)

A cubic function generator is an essential component in TCXOs to compensate for the frequency variation of quartz resonators during temperature change. The authors present a fully analog CMOS cubic function generator circuit. It is composed of analog variable gain amplifiers and a voltage adder. The circuit generates an exact cubic function that represents a quartz resonator’s frequency versus temperature characteristic. Adjusting the parameters of the cubic wave and adding the higher order terms for more precise control can be done easily in this design. The design is implemented and fabricated in TSMC 0.35 μm technology.