i. Input offset voltage: When an op-amp is used as a dc amplifier, it is seen that there is some output dc voltage even though the input dc voltage is zero. Input offset voltage is defined as the voltage that must be applied between two i/p terminals of an op-amp to make its output voltage zero.
ii. Differential input resistance is defined as the equivalent resistance that can be measured at either inverting or non-inverting input terminals with the other terminal connected to ground.