PURPOSE: To perform the fine adjustment of frequency in a wide range without using a trimmer capacitor by putting a parallel circuit consisting of a variable resistor and a capacitor between the input terminal of an inverter and the capacitor.
CONSTITUTION: The subject oscillating circuit consists of a feedback resistor 3 connected in parallel between the input terminals of a CMOS inverter 2, a piezoelectric vibrator 1, a stabilizing resistor 4 connected between the vibrator 1 and the inverter 2, and the oscillating capacitors 5 and 7 which are connected between the earth and the vibrator 1. The inverter 2 and the resistor 3 serve as an amplifier, and the capacitors 5 and 7 and the vibrator 1 form a feedback circuit which prescribes the oscillation frequency. Then a capacitor 8 and a variable resistor 9 which are connected between the capacitor 7 and the input terminal of the inverter 2 function as a frequency fine adjusting element respectively. The capacity varies between the input terminal of the inverter 2 and the earth with change of the resistance value of the resistor 9. Then the fine adjustment of the oscillation frequency is attained like a trimmer capacitor.
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OISHI JUNJI
SAKURADA HIROTSUGU
KOYO PRECISION CO LTD