| 摘要 |
PURPOSE:To eliminate deterioration in noise characteristics by connecting s signal-ground side balanced circuits between two balanced circuits connected in series between one of balanced reception outputs and the signal ground so that a voltage division output which is divided to 1:k is obtained at a differential transmitting amplifier with gains which are -k and (1+k) times. CONSTITUTION:In a two-wire and four-wire converting circuit which has balanced reception outputs and differential transmission inputs, the balanced reception outputs are connected to the terminals of a two-wire side circuit through terminating resistances R/2 which have a value a half as large as a terminal value R respectively, and two balanced circuits Z1 and Z2 are connected in series between one of the balanced reception outputs and the signal ground. In this case, Z2/Z1=Z/R holds as balancing condition and when the gain of the transmitting amplifier 1 needs to be (k) times, the gain l of the amplifier 2 is set to k/(1+k); and then the output voltage V0 zero is V and there is no detouring, thereby obtaining a hybrid balanced state. Further, the amplifier 3 is omitted when some elements of the balance constant of the signal-ground side balance circuit Z2 are divided to 1:k. Then, constants r1 and kr1 can be set up to about 60 kOMEGA and deterioration in noise characteristics is eliminated.
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