| 摘要 |
PURPOSE:To give a function of cancelling a DC offset voltage by inserting a capacitor between an amplifier output of D/A converter comprising a capacitor array and a switch array and an inverting input so as to switch the capacitor by the switch. CONSTITUTION:A compensation capacitor C0 is inserted between an output of the amplifier 2 and the inverting input via a switch S5 in the D/A converter comprising a series circuit consisting of plural capacitor arrays 1 and a switch S array 3 and the amplifier 2. Switches S1-S4, S6 are inserted respectively between a non-inverting input of the amplifier 2 and ground, between the S array 3 and ground, between an output of the amplifier 2 and the S array 3, between the output of the amplifier 2 and the inverting input and between the C0 and ground. In closing the S1, S3, S5 and opening the S2, S4 and S6, the charge in the C0 is changed by switch noise, an offset cancellation error voltage VF is generated and stored in the capacitor array 1. In closing the S2, S5 and opening the S1, S3, S4 and S6, the charge in the capacitor array 1 is distributed to a parasitic capacitor Cx, but this value is small and a residual offset voltage is also decreased. |
