| 摘要 |
PURPOSE:To set freely the polarity of an output current and potential by separating an output current having a current value proportional to an input voltage from a voltage/current converting section to which the input voltage is inputted by an electrooptic converting circuit. CONSTITUTION:An emitter of a transistor (TR)Q1 for converting voltage into current is fed back to an inverting input of an operational amplifier circuit A and its potential is nearly equal to an input voltage VIN. Thus, a collector current of the TRQ1 is VIN/R when an offset voltage of the operational amplifier A is 0 and proportional to the input voltage VIN. This current flows to the electrooptic converting element LD as a current having the identical value to the current of a TRQp in a photocoupler in the ideal case. Thus, the photoelectric converting circuit being an output system is separated electrically from the pre- stage so as to set optionally the potential of the output system.
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