输入偏置电流消除电阻—您真的需要它们吗？

输入偏置电流消除电阻—您真的需要它们吗？


Input Bias Current Cancelation Resistors—do you really need them?
Bruce Trump
Do you add a resistor to match the DC resistance at the inputs of your op
amp circuits?  Check the circuits in figure 1 below. Many of us were
instructed to add Rb as “good practice,” making its value equal to the
parallel combination of R1 and R2. Let’s look at the reason for this
resistor and consider when it’s appropriate and when not.
[pic]
The purpose of Rb is to reduce the voltage offset caused by input bias
current. If both inputs have the same input bias current, equal current
flowing through equal resistances will create equal and opposite offset
voltages. Thus, input bias current will not contribute to the offset
voltage of the circuit. The basic idea is