| 摘要 |
<p>PURPOSE:To attenuate a power source noise sufficiently, by connecting a capacitor in a parallel to a bias resistance between a power source and the base of a transistor for current supply. CONSTITUTION:Capacitors 14 and 15 are connected in parallel to bias resistances 9 and 10 between bases of transistors 3 and 4 for current supply and positive and negative terminals of a power source 12. Impedances of capacitors 14 and 15 are set to a value sufficiently smaller than resistances 9 and 16 and resistances 10 and 17 respectively. When a noise is superposed to the power source 12, this noise is flowed through a path of the power source 12-the capacitor 14-the resistance 14-the capacitor 11-the resistance 17-the capacitor 15-the power source, but a voltage due to this noise is almost applied to resistances 16 and 17. Consequently, the voltage between bases and emitters of transistors 3 and 4 is not affected, and therefore the noise is not leaked to the side of a telephone set 13. Thus, the power source noise is attenuated sufficiently.</p> |
