Patent ID: 6265724
Filing Date: 2001-07-24
Classification: G08C

Abstract:
A galvanic isolation coupling of a current loop comprising an oprational amplifier as a part of the current loop and an optoisolator comprising two receivers, wherein the isolation coupling also comprises a first resistance that is connected in series as a part of the current loop together with an operational amplifier and a transmitting LED of an optoisolator such that a second pole of the resistance is coupled to a positive voltage feed point of the operational amplifier and the anode of the transmitting LED is coupled to a negative voltage feed point of the operational amplifier, whereby the current loop is closed via the cathode of the transmitting LED, the coupling additionally comprisinga parallel coupling of a zener diode and a capacitor arranged between the positive and the negative voltage feed points of the operational amplifier such that the cathode of the zener diode is coupled to the operational amplifier's positive voltage feed point which is further coupled to the positive input of the operational amplifier,a photodiode whose anode is coupled to the operational amplifier output and cathode to the cathode of the transmitting LED,a second resistance whose second pole is coupled to a first pole of the first resistance and a second pole is coupled to a negative input of the operational amplifier, whereby the cathode of a first receiving PIN diode of the optoisolator is coupled to a negative input of the operational amplifier and the anode is coupled to the cathode of the transmitting LED, anda circuit which is galvanically isolated from the current loop and which comprises a second receiving PIN diode of the optoisolator.