Signal compensation is a common technique used to fix variations in a signal. One common signal compensation technique is frequency compensation which can be employed to rectify variations in the frequency of an output signal. For example, in amplifiers, frequency compensation is used to control frequency variations due to overshoot, ringing effects, as well as to ensure no positive feedback occurs in designs employing feedback. Other devices such as signal generators also employ frequency tuning mechanisms to generate a desired output signal. Frequency compensation is particularly important for timing and signal generating devices such as oscillators and resonators since the output of such devices can be very sensitive to frequency variations and the precision of a signal can be important for applying and utilizing timing devices.
Frequency variations can occur due to a number of factors depending on the device and/or system being used. In packaged devices, these factors can include thermal variations, package-induced stress, process-induced stress, pressure variations, and drive effect (stress due to bias). Additional factors such as nonlinearity, system noise, gas-induced friction, and material-dependent properties (e.g., stiffness, fatigue and creep) can determine how much a signal's frequency will vary. The effect of these factors can become more dominant as the system size decreases to micron and sub-micron levels, and in particular, if the devices are packaged with a wafer-level packaging approach. Since technology and market demands have driven integration of broadband capabilities into nano-scale devices, frequency compensation techniques have become important for proper operability of devices.
Several frequency compensation techniques currently exist. However, most standard compensation techniques, and in particular those used with quartz oscillators, have shortcomings, for example, in providing adequate compensation over a large spectral range. There is a need to develop improved compensation techniques.