| 摘要 |
<p>PURPOSE:To eliminate the noise of a power supply and to extend the range of distance of a subscriber line, by providing a constant current source which flows a constant current compensating a voltage drop of a current mirror circuit and a power supply noise rejection circuit superimposingly on the current mirror circuit. CONSTITUTION:In a subscriber circuit supplying a current IL to a load ZL including a subscriber telephone circuit connected between lines A and B, a constant current source CNI which flows a constant current I0 compensating a voltage drop due to current mirror circuits A-C, A'-C' and a power supply noise rejection circuit consisting of filters R1, R2, C1 superimposingly on the current mirror circuit, is provided, allowing to compensate the voltage drop even if a subscriber circuit consists of a plurality of current mirror circuits and to obtain the similar feeding characteristics as the direct feeding to the load ZL with a power supply voltage VBB. Further, the constant current source CNI, the current mirror circuit and transistors Q1, Q2 are made coincident with the temperature characteristics, allowing to constitute the integrated circuit on the same silicon chip.</p> |
