| 摘要 |
PURPOSE:To obtain the larger maximum output of speech reception as the distance of a telephone circuit is smaller by connecting a load resistance of a differential amplification stage via a current mirror circuit in order to increase the output amplitude at a differential stage. CONSTITUTION:At a differential amplification stage DA', a terminal at one side of a constant current source I1 is connected to a line terminal L1. The output of the source I1 is connected to the emitters of pnp transistors (TR) Q5 and Q6 respectively, and TRQ11 and Q12 are connected to the input stage of the stage DA'. The collectors of TRQ11 and Q12 are connected to the terminal L1 with the emitters connected to the outputs of constant current sources I4 and I5 as well as to the bases of the TRQ5 and Q6. The TRQ7 and Q8 (TRQ9 and Q10) from a current mirror circuit, and the collector of the diode-connected TRQ7 (Q9) is connected to the collector of the TRQ5 (Q6) of a differential stage. A resistance R1 (R2) and the base of a TRQ3 (Q4) are connected to the collector of a current leading TRQ8 (Q10). |
