feat: add opamp internal diagram

Final.tex

@@ -49,20 +49,37 @@ Please observe the conference page limits.
   \caption{A first-order high-pass filter}
   \begin{circuitikz}[american voltages]
    \draw
-    (0,2) node[above=0.2cm]{$v_{in}$} to [short, o-] [R, l_=$R_1$] (1.5,2) coordinate (IN)
+    (0,2) node[left=0cm]{$v_{in}$} to [short, o-] [R, l_=$R_1$] (1.5,2) coordinate (IN)
     (3,3) to [R, l_=$R_2$] (5.375,3) coordinate (FB)
     (3,2)
     node[op amp, noinv input down, anchor=-](OA) {}
-    (OA.-) to [short, *-] ++(0, 1)
+    (OA.-) to [short, o-] ++(0, 1)
 
     (OA.-) to [C=$\frac{1}{sC}$] (IN)
-    (OA.+) to ++(0,-0.5) node[ground]{}
+    (OA.+) to  [short, o-] ++(0,-0.5) node[ground]{}
     (OA.out) to ++(0, 0) coordinate (OUT) to (FB)
-    (OUT) to [short, *-o] ++(1,0) node [right=0.2cm]{$v_{out}$}
+    (OUT) to [short, *-o] ++(0.5,0) node [right=0.2cm]{$v_{out}$};
+    \node (v_p) [above=0cm] at (OA.+) {$v_p$};
+    \node (v_p) [below=0cm] at (OA.-) {$v_n$};
     ;
 \end{circuitikz}
 \end{figure}
 
+A more accurate representation of the op-amp foregoes the assumption,
+oft made regarding op-amps wired in a feedback configuration, that
+$v_n = v_p$. Avoiding this assumption requires a more precise
+description of the properties of the op-amp itself, describing its
+input resistance $R_i$, output resistance $R_o$, and the relationship
+between the input and output - the open-loop gain $A$. Figure
+\ref{img:opamp_internal} depicts such a model.
+
+\begin{figure}[h]
+  \caption{A more accurate depiction of an op-amp}
+  \label{img:opamp_internal}
+  \centering
+  \includegraphics[width=0.4\textwidth]{opamp_internal}
+\end{figure}
+
 \section{Ease of Use}
 
 \subsection{Maintaining the Integrity of the Specifications}