Integrated cct. quartz oscillator - external crystal RC tuning cct. resistor laser trimmed for high precision

摘要

The quartz oscillator consists of an integrated circuit as oscillator and an external quartz crystal coupled to an external tuning circuit. The tuning circuit consists of a capacitor (C3) connecting one side of the crystal to OV and a variable resistor (R) shunting the crystal (Q). The capacitor value is chosen to give a coarse setting to the frequency, and the resistor is then adjusted for the fine setting. The variable resistor is trimmed using a laser or by similar precise method. The advantage lies in the RC trimmer circuit giving better precision than the more usual trimming methods usign solely capacitors. It also lends itself well to mass production techniques.