| 摘要 |
<p>Resistive circuits (32,22) are provided at the input of an electronic battery feed circuit feedback path for lowering the voltage level of feedback signals to a metallic signal feedback portion and a common mode signal feedback portion so a common mode amplifier (36) can be implemented in a much lower voltage technology than line amplifiers (17,18) of the battery feed circuit. Additional resistive circuits (47,52) at the feedback output apply metallic signals to complementary inputs (+18,-17) of the tip and ring line amplifiers without requiring a phase splitting amplifier, In addition, signals derived from the feedback circuit are used (signal on lead 59; 30) to vary the supply voltage for the line feed circuit elements as a function of feedback signal level and to provide a common mode reference signal (58) which causes the tip and ring amplfiers to be biased symmetrically with respect to ground and the variable negative supply.</p> |
