| 摘要 |
PURPOSE:To form the means to achieve the automatic zero correction for the A/D converter in A/D operation with current mode through inversion and conversion of analog input current, by providing the voltage current converter and holding capacitance connected to one input. CONSTITUTION:The output current of the voltage current converter consisting of the differential amplifier 7, FET8 and resistor 6 and to one input of which one end of the holding capacitor 1 is connected, outputs from the drain terminal 9 of FET8 and is fed to the input terminal of the current inversion circuit 10, and the output terminal 12 of the circuit 10 is connected to the first current source 13, reference current source 15 and integrator 20 (consisting of amplifier 22 and integrating capacitor 21). On the other hand, the feedback loop is constituted from the terminal 12 to the common connection of the amplifier 7 and the capacitor 1 via the switch SW6. Thus, the output current of the voltage current conversion is gradually increased with the compensation voltage stored in the capacitor 1, thereby increasing the output current of the circuit 10 and finally making almost in agreement with each other. That is, the error of the differential current is reduced ex ponentially to achieve zero correction. |
