| 摘要 |
PURPOSE:To reduce an input offset voltage by providing an amplifying circuit on the respective input ends of a differential amplifying circuit, in a voltage comparator for further amplifying the output of the differential amplifying circuit in which one end of a switch is connected to the input end. CONSTITUTION:First of all, switches (SW)1a, SW2a, SW1, SW2 and SWA are closed and an input voltage V1 is applied to amplifying circuits 5, 6, and input and output ends of a differential amplifier 2 are brought to self-bias. Subsequently, the SW1 and the SW2 are opened and a noise charge flows into input ends of the circuits 5, 6. Therefore, input voltages of the circuits 5, 6 are varied, and this variation is absorbed by capacitors 3, 4. Next, the SWA is opened, the SW2b and the SW2 are closed, and an input voltage V2 is applied. Also, the SW2 is opened and the noise charge flows into the input end of the circuit 6, and the input voltage of the circuit 6 is varied. A voltage difference after this variation is amplified and outputted by differential amplifiers 1, 2. In such a way, an input offset voltage can be reduced.
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