| 摘要 |
PURPOSE:To extend the service life of a nonvolatile memory by rewriting the nonvolatile memory so as to reduce number of times of the rewrite remarkably only when the variable resistor value optimized by the user is set. CONSTITUTION:In varying the variable resistor normally, it is not stored in the nonvolatile memory 20 and only the value of the variable resistor desired to be set at application of power is stored in the memory 20 by using a storage switch 21. The count output of an up/down counter 19 is supplied to a switch control circuit 6 through a counter output line 17, a switch of a switch array 3 is controlled via the circuit 6 to change over the switch array 3 connected to a resistance circuit network 2 so as to decrease or increase the value or the input resistance of the amplifier 4. Thus, the amplification factor of the amplifier 4 is increased or decreased and the result is fed to a signal output 5. In applying power, a power monitor circuit 15 detects the leading of the power supply and the content of the memory 20 is read by the counter 19 as a preset value. The setting value is stored in the memory 20 in this way and the variable resistor value is set in applying power.
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