| 摘要 |
PURPOSE:To switch a loopback gate independently of ununiformed base-emitter voltage VBE of a differential pair transistor(TR) and the dispersion in a resistor deciding a reference voltage by turning ON/OFF a current of a constant current source of a CML differential amplifier section. CONSTITUTION:In case of applying loopback in an optical repeater, a low level loopback control signal is inputted to a control section 3 via an input terminal 10. The control section 3 sets the current of the constant current source 2 of a CML(Current Mode Logic) differential amplifier section 1 by the signal to operate the CML differential amplifier section 1. Then loopback signals 1, 0 at the input terminal 14 are ON/OFF with respect to a reference voltage V and outputted from the output terminal 17. Since the CML differential amplifier circuit is used and the constant current source is subjected to ON/OFF by the constant current source of the CML differential amplifier circuit and a loopback control signal sent from a terminal station in this way, sure gate switching in the optical repeater is attained. |
