This low cost, crystal-controlled oscillator uses one TTL gate. Two factors ensure oscillator start-up: The connection of NAND gates G1, G2, and G3 into an unstable logic configuration and the high loop gain of the three inverters. Values of R1, R2, C1, and C2 aren`t critical;
select them so the oscillator operates at a frequency 70 to 90% higher than the crystal frequency when the crystal is disconnected. For 1-2 MHz operation, a low-power 54LOO IC is recommended; for a 2-6 MHz, a standard 5400 type; and for 6-20 MHz, a 54HOO or 54SOO.