| 摘要 |
PURPOSE:To remove a power supply noise with a small number of elements by connecting between the inverted inputs of two operational amplifiers by a serial circuit consisting of a resistor and a DC interrupting capacitor and mutually using voltages appearing in respective inverted inputs in common. CONSTITUTION:The respective inverted inputs of the operational amplifiers OP1, OP2 are connected by the serial circuit consisting of the resistor R8 and the capacitor C. The voltages V1, V2 appearing the intermediate nodes (a), (b) can be expressed by the formula when the noise voltage is defined as Vn. The voltages V1, V2 appear also in the inverted inputs of the operational amplifiers OP1, OP2 and prevent resistors R4, R5 from the inflow of noise current. To turn the noise current actually to zero, voltages V3, V4 are set to zero and Vn respectively. Thus, efficient power supply can be attained by selecting R6, R7 and R8 so that R1/R2=R6/R8, R3/R2=R7R8, i.e. R1/R6=R2/R8= R5/R7 are formed. |
