| 摘要 |
PURPOSE:To prevent the influence of variance in variable resistance from extending to an operational amplifier input by connecting one resistor to each terminal of a variable resistor, connecting a resistor in parallel to the variable resistor, and setting the resistance value of the variable resistor largest among other three resistance values. CONSTITUTION:The resistance value of the variable resistor 1 is much larger than the resistance value r4 of a resistor 4 connected in parallel to it at room temperature, so the composite resistance is r4. When a voltage V0 is applied to a point C, voltages (r3+r4)V0/(r2+r3+r4) and r3V0/(r2+r3+r4) are developed at points A and B. In the expressions, r2 and r3 are the resistance values of resistors 2 and 3. Consequently, the output of the variable resistor 1, i.e. the voltage at a point D varies between both voltages and almost no influence is exerted upon the resistance value of the variable resistor 1. |
