8.2.2 Crystal Oscillator

A simple crystal oscillator using the LMV7239-Q1 is shown in Figure 27. Resistors R₁ and R₂ set the bias point at the comparator’s noninverting input. Resistors, R₃ and R₄ and capacitor C₁ set the inverting input node at an appropriate DC average level based on the output. The crystal’s path provides resonant positive feedback and stable oscillation occurs. The output duty cycle for this circuit is roughly 50%, but it is affected by resistor tolerances and to a lesser extent by the comparator

Figure 27. Crystal Oscillator