| 摘要 |
PURPOSE: To provide a subscriber line interface circuit which reduces overall heat generation and heat consumption in an integrated circuit. CONSTITUTION: A subscriber line interface circuit 100 includes an output stage 10 having a pair of differential mutual conductance amplifiers 12 and 14 to drive a chip and a ring line of a telephone exchange. The output stage 10 includes a circuit which reduces power consumption in the integrated circuit in the case of a relatively low subscriber loop impedance. An off-chip resistor 102 is connected to a negative voltage rail from the output line of the ring line amplifier 14. When the loop impedance is low, a relatively large voltage drop is established through the resistor 102. Since the resistor 102 given as an off-chip register and the direction flowing to the ring line amplifier 14 is changed in other modes, overall heat consumption in the integrated circuit is reduced. |
