Intrinsically safe opto-coupler circuit having an optimum data transmission rate

A signal processing system that provides signal isolation between input signals and output signals of said system; said system including means for converting electrical input signals to optical signals and further comprising means for converting said optical signals to electrical output signals comprising: a photo-transistor having a base responsive to the receipt of optical signals for, controlling the collector current of said photo-transistor; a first resistor connecting the collector of said photo-transistor to a voltage source; a diode comprising an emitter-base junction of a second transistor connected in parallel with said first resistor; said diode being effective to prevent saturation of said photo-transistor as well as to control the collector current of said second transistor; a second resistor connecting the collector of said second transistor to ground; the voltage developed across said second resistor in response the reception of said optical signals by said base of said photo transistor being said output signals.

A system for providing AC and DC signal isolation between input signals and an output signals of said system comprising: an opto-isolator comprising means for converting electrical input signals received from a source to optical signals and further comprising means for converting said optical signals to electrical signals; said means for converting said optical signals to electrical signals comprising: a photo-transistor having a base responsive to the receipt of optical signals for controlling the collector current of said photo-transistor; a first resistor connecting the collector of said photo-transistor to a voltage source; a diode comprising an emitter-base junction of a second transistor being connected in parallel with said first resistor; said diode being effective to prevent saturation of said photo-transistor as well as to control the collector current of said second transistor; a second resistor connecting the collector of said second transistor to ground; the AC voltage developed across said second resistor in response the reception of said optical signals by said base of said photo-transistor being said output signals of said system.

A method of operating a system providing AC and DC signal isolation between input signals and output signals of said system; said system including means for converting electrical input signals received from a source to optical signals and further comprising means for converting said optical signals to electrical output signals; said method comprising the steps of: applying said optical signals to a base of a photo-transistor; controlling the collector current of said photo-transistor in response to the receipt of said optical signals; connecting a first resistor between the collector of said photo-transistor to a voltage source; connecting a diode comprising an emitter-base junction of a second transistor in parallel with said first resistor; said diode being effective to prevent saturation of said photo-transistor as well as to control the collector current of said second transistor; connecting a second resistor between the collector of said second transistor to ground; the voltage developed across said second resistor in response the reception of said optical signals by said base of said photo transistor being said output signals.