Overtone crystal oscillator automatic calibration system

An overtone crystal oscillator automatic calibration system including an overtone crystal oscillator with multiple programmable resistors and multiple amplifiers with supply voltage inputs and a calibration system. The calibration system adjusts the programmable resistors and the supply voltage inputs and detects oscillation of the overtone crystal oscillator. The calibration system adjusts the programmable resistors and the supply voltage input for each of multiple sequential steps to adjust the frequency bandwidth, such as from a higher bandwidth and lower gain to a lower bandwidth at higher gain. For example, each resistance level is tested for each of multiple supply voltage levels. The range of resistances and voltages is designed to ensure oscillation at a selected overtone frequency while avoiding oscillation at a fundamental frequency of the oscillator crystal. Oscillation may be detected by a counter which counts to a predetermined count value indicating successful oscillation.