| 摘要 |
PURPOSE:To prevent parasitic oscillation by inserting a resistor in series with a positive feedback capacitance and increasing comparatively the ratio of the feedback quantity at the fundamental resonance frequency of a resonator to the feedback quantity in the parasitic resonance frequency. CONSTITUTION:A resistor R and a positive feedback capacitor C are connected in series as a feedback circuit 11 between the collector of the 2nd transistor (TR) Q2 and the base of the 1st TR Q1. The feedback capacitor C is realized as a value of nearly 5pF and in selecting the resistor R as about 15kOMEGA, the series impedance (R+1/jomegac) comprising the resistor R and the capacitor C of the feedback circuit is nearly 71.6kOMEGA at the fundamental frequency and nearly 16.6kOMEGA at the parasitic resonance frequency. Thus, the feedback quantity of the fundamental resonance frequency is nearly unchanged by adding the resistor R but the feedback quantity at the parasitic resonance frequency is decreased by >= nearly 6dB (attenuated), then the parasitic oscillation is prevented. |
