Nonlinear contribution to oscillation-frequency sensitivity in RC integrated oscillators

The sensitivity of oscillation frequency of integrated oscillators to varying parameters or elements is usually so high for simple designs that the advantages of integrated circuits are completely offset. Satisfactory performance can be achieved for some applications by the use of low-temperature-coefficient thin-film components; by the use of the temperature tracking of elements in monolithic circuits; and by the use of active compensation circuits. These methods are in general based on a linear model of the oscillator and often require amplifiers with very insensitive gain characteristics or the inclusion of automatic gain control (AGC) circuits. This paper describes a compensation technique can be used in conjunction with linear techniques to reduce second- order contributions to sensitivity of frequency to bias and to gain. An experimental oscillator is described that uses this compensation technique. It has a zero of oscillation-frequency sensitivity to manually set gain changes and an order-of-magnitude decrease in frequency deviation over the described gain range. All the required compensating nonlinear functions are realized by diode-resistor networks.