| 摘要 |
PURPOSE:To improve the accuracy of comparison with simple constitution by providing an amplifier circuit whose amplification gain is selectable, a comparison voltage setting circuit whose comparison voltage is selected corresponding to the gain selection and a comparator comparing the set comparison voltage with the output voltage of the amplifier circuit. CONSTITUTION:The amplifier circuit 20 is provided with a logarithmic amplifier 4, a bias voltage VB is fed to transistors (TRs) 26, 28 via a switch circuit 30 to switch the gain of the amplifier circuit 20. Output voltage Va0, Vb0 of the amplifier circuit 20 are fed to comparators 341-346 by the selection of the amplification gain and compared with comparison voltages Va1-Va6 or Vb1-Vb6 set by a comparison voltage setting circuit 36. The circuit 36 is provided with a voltage division circuit composing of two sets of series circuits and a switch circuit 24 to set the comparison voltages. Then switch circuits 30, 42 are switched in response to an input voltage VIN. Since the voltage level to be compared and the comparison voltage level are changed relatively, a comparison output with high accuracy is obtained over a wide range of the input voltage.
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