| 摘要 |
<p>PURPOSE:To miniaturize and economize a subscriber circuit and to make into LSI and so on by constituting so that when a necessary terminal impedance is ZT, a feed-back impedance comes to be NZT which is N-times of ZT, and constituting similarly so that a balance network impedance ZB comes to be NZB which is N-times of it. CONSTITUTION:A voltage V0 between terminals L1 and L2 on which a subscriber terminal is connected is added to a received voltage VRX. This voltage is amplified to be NZB/(R1+NZT). And VRX is subtracted from the result of the addition of V0 and VRX, and further a difference between said result and the amplified result of NZB/ (R1+NZT) is calculated and a sending voltage VTX is obtained. The above-mentioned summed voltage is potential-devided by a load R1, and this potential difference is amplified to A0times, further, is summed with a reference voltage VF, amplified to A1times, and supplied to loads R2 and R3. In this way. by constituting so that an impedance which is of prescribed number times of the terminal impedance is made to be the feed-back impedance of an amplifier, a capacitor can be realized in the scale of a fraction one by prescribed number times, and so, the subscriber circuit can be easily miniaturized, economized and made into the LSI.</p> |
