2. DC errors and superposition
Figure 1. Op amp internal DC model
Connect Figure 1 in a non-inverting amplifier (AN-7 names this “Follower with gain (electrometer amplifier)”).
\[v_{OUT} = v_{in}\underbrace{\left(\frac{A_{v0}}{1 + A_{v0} \dfrac{R_1}{R_1 + R_2}}\right)}_\text{gain} + \underbrace{\biggl(V_{OS} + I_{B+} R_{eq+} - I_{B-} R_{eq-}\biggr)\left(\frac{A_{v0}}{1 + A_{v0} \dfrac{R_1}{R_1 + R_2}}\right)}_\text{offset}
\label{dcout}\]