| 摘要 |
<p>In a current level sensing circuit employing a gyrator to control an opto-isolator, a coupling circuit having an input impedance of a magnitude sufficiently higher than the output impedance of the gyrator that it does not substantially load the gyrator is employed to couple the gyrator output to the opto-isolator. In one embodiment, a differential amplifier receives the gyrator output at a first input which is associated with an output that is coupled to the isolator and a predetermined reference voltage supply is applied to a second input of the differential amplifier. A current sink is connected in a common load path portion of the differential amplifier and is otherwise connected to implement differential amplifier current limiting at a level which assures damage-free operation of the isolator as well as insensitivity to low amplitude electrical disturbances applied to the gyrator. Circuitry for unbalancing the amplifier operation can be used to provide an hysteresis effect in the current transfer function of the amplifier. <IMAGE></p> |
