PURPOSE: To compensate the variation of an AC output signal by automatically controlling a damping value by applying a DC voltage, to a difference in the current transmission factor of a photocoupler and temperature and aging changes, to an attenuator using FET.
CONSTITUTION: For an AC signal transmission circuit, two photocouplers 4 and 5 are used and their output voltages are applied to attenuation circuit 10 with operational amplifier 13 and FETs F0 and F1, so that an output voltage when photocouplers 4 and 5 are equal in current transfer factor and that including variation when they differ in factor will be outputted as the DC output voltage of operational amplifier 13. The output voltage including this variation is extracted by DC voltage extraction circuit composed of resistances R4 and R5, and capacitor C0 and the output of this circuit 9 is applied to the gate of FETF1; and resistance R4 and R5 are set to fix the ON resistance of FETF1 to a fixed value, and the attenuation value of attenuation circuit 10 is automatically controlled by compensate variation of an AC output signal.
| JPS52151542 | SIGNAL TRANSMISSION UNIT |
| WO/2010/032825 | MAGNETIC COUPLING-TYPE ISOLATOR |
AKIYAMA NOBUYOSHI
EHATA MASAKI
NIPPON TELEGRAPH & TELEPHONE