| 摘要 |
PURPOSE:To obtain a comparison circuit with high accuracy, stable against the fluctuation of a power supply voltage, by providing a compensating means of an input offset voltage and a sample holding function and compensating a step error due to the switching of a switch at an input terminal. CONSTITUTION:SW1, 14 and 20 are closed at time t0 and a SW2 is opened. Charges of VA1, C1, 1/2e1G1C2, -1/2e1G1C2 are stored respectively in capacitors 4, 22 and 23, where C1, C1, C2, C2 are values of capacitors 4, 21, 22, 23, G1, G2 are voltage gains of differential amplifiers 11, 12, VA1, VA2 are the 1st and 2nd analog input voltages and e1, e2 are input offset voltages. Through the shifting of off-time of each SW, the SW20, 14, 1 are opened respectively as t1, t2 and t3 and the SW2 is turned on at t3, then the potential difference of the input to the amplifier 12 is G1(VA2-VA1) and the voltage e1 is compensated. The output voltage of the amplifier 12 is V0=G1G2(VA2-VA1+e2/G1) and the input offset voltage e2/G1 can be reduced. Further, the step error can be compensated by adding the capacitor 21. |
