Fundamental/Overtone Crystal Oscillator

The schematics show two crystal oscillator circuits constructed using the high-speed LT1394 comparator from Linear Technology (www.linear-tech.com). In each case the crystal is in the positive feedback path, while in the negative feedback path an RC network provides the necessary phase lag.Circuit (a) is designed to use AT-cut crystal oscillating at its fundamental frequency and is suitable for operation over a frequency range from 1 MHz to 10 MHz.