| 摘要 |
<p>PURPOSE:To decrease the cost by eliminating a circuit element with high dielectric strength required hitherto for a conventional loop current supply circuit. CONSTITUTION:An output of current mirror circuits 43, 44 is connected as a current source current of differential aplifier amplifiers 45, 46 constituted respectively by transistors (TRs) 1-4 and an input current of the current mirror circuits 43, 44 flows to a power source V through the input side of the current mirror circuit 44, ground, a resistor R11 and the input side of the current mirror circuit 43. The output current of TR3 of the differential amplifier 46 goes to an input current of the current mirror circuit 41 placed at the power source V side and a collector output current of the TR1 of the differential amplifier 45 goes to the input current of the current mirror circuit 42. Moreover, the current mirror circuits 41, 42 have an amplification factor K1 and supply a DC loop current to the subscriber line side.</p> |
