| 摘要 |
PURPOSE:To obtain a device including a chopper amplifier circuit which cancels an offset voltage and is not affected by a storage capacitor, by storing the offset voltage of an operational amplifier circuit in the capacitor and inverting the offset voltage at the amplification timing to feed back it to the input side. CONSTITUTION:The output terminal of an operational amplifier circuit OP2 is connected to one electrode of a capacitor C9 through a switch phi2 for the purpose of preventing the offset voltage in both operational amplifier circuits OP1 and OP2 from having influences upon the chopper amplifying operation. This electrode of the capacitor C9 is connected to the earth potential point of the circuit through a switch phi4. At the timing when the switch phi4 is turned on, a switch phi24 is turned on. Then, an input signal SR is added to an input signal Sa with a polarity opposite to that of the signal SA, and therefore subtraction is performed. The offset voltage held in the capacitor C9 is supplied with the opposite polarity, and offset components are cancelled by subtraction.
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