| 摘要 |
PURPOSE:To obtain a stable and good narrow band characteristic dependent upon two frequencies by connecting two series circuitts, which consist of crystal vibrators different in resonance frequency and resistance, to a differential amplifier circuit in an opposite phase relation and eliminating the parallel capacity peculiar to the rystal vibrator. CONSTITUTION:A series circuit consisting of crystal bivrator 12 and resistance 14 and a series circuit consisting of crystal vibrator 13 and resistance 15 are connected between the input end of signal generator 11 and the in-phase input end of differential amplifier circuit 18 and between the input end of generator 11 and the anti-phase input end of circuit 18 respectively. Then, resistance values of resistances 14 and 15 and resistance values of resistances 16 and 17 are set to be equal to each other respectively. Since crystal vibratiors 12 and 13 are different in resonance frequency and have the same production method, namely, the same crystal piece supporting method and the same shield case, parallel capacities peculiar to crystal vibrators are cancelled by each other. As a resul, a stable and good narrow band characteristic dependent upon two frequencies can be obtained. |
