| 摘要 |
PURPOSE:To correct the offset voltage of an operational amplifier and improve the linearity at a light load level by using two operational amplifiers and one comparator so that the operational amplifiers alternately perform integration and the correction of the offset voltage. CONSTITUTION:When analog switches S1-S8 are ON, and analog switches S11- S18 are OFF, a capacitor C2 is charged with the offset voltage of an operational amplifier A1. On the other hand, an operational amplifier A2 becomes an integrator and integrates an input signal es. When the integral voltage reaches eref, a comparator circuit A3 is inverted, and a flip-flop circuit FF is triggered. Consequently, the analog switches S1-S8 are simultaneously turned OFF, while the analog switches S11-S18 are simultaneously turned ON, so that the operational amplifier A1 integrates the input signal es. Thereby, the operational amplifier can correct its own offset voltage. Accordingly, a stable voltage-frequency conversion can be performed on even a signal of light load level. |
