Place an op amp using the input anchor’s position

Question

I have a circuit that consists of a few components, and would like to know how can I draw an op amp without knowing the center position of the op amp.

Here is the code I currently have

Note: This is extremely simplified, I have many more components in the drawing.

\documentclass{standalone}
\usepackage{circuitikz}

\begin{document}
\begin{circuitikz}[american]
    \draw (0, 0) to[R=$R_s$, *-*] ++ (0, -3) coordinate (vp) ++ (0, -3) to[zzD=$v_Z$, *-] ++ (0, 3);
    % How to initialise the op amp on the RHS of the resistor and Zener diode?
    \node[op amp, yscale=-1] (opamp) {};
    \draw (opamp.+) to[short] (vp);
\end{circuitikz}
\end{document}

Output:

As you can see, the op amp initialises at the origin, and vp does not go to the RHS of the node between the resistor and diode.

Here is what I would like:

As you can see, the "center" anchor of the op amp is unknown, so how can I initialise the op amp using the positive input anchor (which is known)?

Thanks in advance.

Answer 1

You draw the wire and then position the op-amp with the appropriate anchor:

\documentclass{standalone}
\usepackage{circuitikz}

\begin{document}
\begin{circuitikz}[american]
    \draw (0, 0) to[R=$R_s$, *-*] ++ (0, -3) coordinate (vp) ++ (0, -3) to[zzD=$v_Z$, *-] ++ (0, 3);
    % How to initialise the op amp on the RHS of the resistor and Zener diode?
    \draw (vp) -- ++(2,0) node[op amp, yscale=-1, anchor=+] (opamp) {};
\end{circuitikz}
\end{document}

Although is better to use

\draw (vp) -- ++(2,0) node[op amp, noinv input up, anchor=+] (opamp) {};

instead of yscale=-1, for reasons explained in the manual around page 19 (as for the current version):