ELECTRICAL ISOLATORS

摘要

The invention discloses an electrical isolator circuit comprising: an input stage comprising a transmitter of an opto-isolator; and an output stage comprising: a receiver of the opto-isolator; an active circuit in series with the receiver between the receiver and a power rail of the output stage; a first resistor connected to an output of the active circuit, and an input for the application of a predetermined voltage to the active circuit, the output stage being configured such that a varying output voltage is developed across the first resistor in response to input of a high voltage AC signal to the input stage. Ideally the output stage is operable to clamp the voltage across the receiver at the level of the predetermined voltage, thereby allowing for an increase in the load resistor and variable output resistor without increasing the time constant to unacceptably having regards to switching requirements.