| 摘要 |
PURPOSE:To decrease the number of windings of a transformer and a coil being a filter element and to attain miniaturization, by connecting an impedance reduction circuit in parallel with a crystal oscilator. CONSTITUTION:An impedance reduction circuit D performing the reduction in an equivalent series impedance is connected in parallel with a crystal oscillator X of a German type crystal filter. This reduction circuit D is formed with an inverting amplifier combined with resistors R1, R2(R1>=R2) and an operational amplifier IC1. Through the provision of the reduction circuit D, the winding ratio of a transformer T'2 for impedance matching is reduced. The number of windings of a coil L'1 is decreased through the provision of the circuit D similarly in the hybrid type crystal filter. Thus, the number of windings of the transformer and the coil being the filter element is decreased and the miniaturization is attained. |
