| 摘要 |
PURPOSE:To miniaturize and economize a feeding part by properly determining a ratio of the resistance value of a fourth resistance to that of a fifth resistance or a ratio of the resistance value of a nineth resistance to that of a tenth resistance. CONSTITUTION:When ground-fault or cross contact occurs in a subscriber's line, the power consumed by the output part of an operational amplifier 16 exceeds the allowable power consumption of one transistor TR. Therefore, a ratio of the resistance value of a fourth resistance 14a to that of a fifth resistance 14b or a ratio of the resistance value of a nineth resistance 24a to that of a tenth resistance 24b is properly determined. Consequently, the power consumption in the output part of the first operational amplifier 16 or a second operational amplifier 26 is reduced to the allowable power consumption of one TR or lower, and it is unnecessary to use plural TRs together. Thus, miniaturization and economization of the feeding part are promoted. |
