Circuitikz schematic scaling issue

Question

I am trying to draw a simple circuit with circuitikz, but in order to better suit my needs I had to modify the size of all components through /tikz/circuitikz/bipoles/length=0.9cm (default length should be 1.4cm). However, when compiling the figure on the left in the mwe below, you see that the shape of the voltage source is not satisfying.

I merged two answers from TeX.SE to try and cope with this, but I obtained the picture on the right, where the shape of the voltage source is indeed ok, but its label is scaled and the starting coordinate of the path is not where I expected it to be! I guess it has to do with the transform shape option, but I do not really know how to circumvent this issue and achieve what I wanted.

\documentclass[a4paper]{book}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage{pgfplots}
\usepgfplotslibrary{external}
\tikzexternalize[prefix=mwe-\overlaynumber-]
\tikzsetexternalprefix{tikzpics/}
\usetikzlibrary{3D, calc, external, positioning, circuits.logic.mux, shapes.gates.logic.US}
\usepackage[americaninductors]{circuitikz}
\begin{document}
\begin{figure}[h]
\centering
\begin{tikzpicture}[auto, node distance=4mm and 4mm, circuit logic,every node/.style={font=\tiny}, >=latex,%
                /tikz/circuitikz/bipoles/length=0.9cm]
    \def\nodedist{4mm}
    \def\complen{9mm}
    \ctikzset{tripoles/mos style/arrows, tripoles/nmos/arrow pos=0.8, tripoles/pmos/arrow pos=0.6,}
\draw (0,0) to [C, name=c] ++(\complen, 0) node[american not port, name=inv1, anchor=in] {};
\node (inv2) [right=of inv1, american not port] {};
\draw ({$(c.east)!.5!(inv1.in)$} |- inv1.in) to [short,*-] ++(0,.7*\complen) to [R] ({$(inv1.out)!.5!(inv2.in)$} |- {$(inv1.out)+(0,.7*\complen)$}) to [short,-*] ({$(inv1.out)!.5!(inv2.in)$} |- inv1.out);
\draw ({$(c.east)!.5!(inv1.in)$} |- inv1.in) to [american voltage source, l=$V_\textup{CM}$] ({$(c.east)!.5!(inv1.in)$} |- {$(inv1.in) + (0,-2*\complen)$});

\draw (inv1.out) -- (inv2.in);

\end{tikzpicture}\hfil
\begin{tikzpicture}[auto, node distance=4mm and 4mm, circuit logic,every node/.style={font=\tiny}, >=latex,%
                /tikz/circuitikz/bipoles/length=0.9cm]
    \def\nodedist{4mm}
    \def\complen{9mm}
    \ctikzset{tripoles/mos style/arrows, tripoles/nmos/arrow pos=0.8, tripoles/pmos/arrow pos=0.6,}
\draw (0,0) to [C, name=c] ++(\complen, 0) node[american not port, name=inv1, anchor=in] {};
\node (inv2) [right=of inv1, american not port] {};
\draw ({$(c.east)!.5!(inv1.in)$} |- inv1.in) to [short,*-] ++(0,.7*\complen) to [R] ({$(inv1.out)!.5!(inv2.in)$} |- {$(inv1.out)+(0,.7*\complen)$}) to [short,-*] ({$(inv1.out)!.5!(inv2.in)$} |- inv1.out);
\draw \pgfextra{\ctikzset{/tikz/circuitikz/bipoles/length=1.4cm, transform shape}} ({$(c.east)!.5!(inv1.in)$} |- inv1.in) to [american voltage source, l=$V_\textup{CM}$, scale=0.6] ({$(c.east)!.5!(inv1.in)$} |- {$(inv1.in) + (0,-2*\complen)$});

\draw (inv1.out) -- (inv2.in);

\end{tikzpicture}
\end{figure}
\end{document}

Answer 1

Well --- first of all, as it is said in the manual at the very start, circuitikz and the internal circuit libraries are basically incompatible. The problem is that there are keys that override each other loading both... let me cite myself:

Anyway, the compatibility code is a best-effort task and only very lightly tested — the authors' advice is to choose one or the other, without mixing them.

I propose a pure circuitikz solution to the circuit --- I really do not know how to do it with the internal library, so I'll let it to somebody else.

Notice that I removed things that are not relevant to the scaling problem (comments in the code). I am not sure of your objective, so I did the second diagram with smaller components by using the class style method, and then changing the size of the "numerical" coordinates with scale (that, without transform shape, it doesn't scale the nodes nor the text).

\documentclass[a4paper]{book}
\usepackage[english]{babel}
\usepackage[T1]{fontenc}% utf8 is standard, T1 not, and you want it
\usepackage{pgfplots}\pgfplotsset{compat=1.18}%never omit the compact key
%\usepgfplotslibrary{external}
%\tikzexternalize[prefix=mwe-\overlaynumber-]% will break outside beamer
%\tikzsetexternalprefix{tikzpics/}
\usetikzlibrary{calc, positioning,}%removed internal circuits libraries
% it seems you want american shapes
\usepackage[americaninductors, american]{circuitikz}
\ctikzset{tripoles/mos style/arrows, tripoles/nmos/arrow pos=0.8, tripoles/pmos/arrow pos=0.6}
\ctikzset{bipoles/length=0.9cm}% This CAN'T BE CHANGED midway a path
% which such a small basic length we have to tweak the font of the generators
\ctikzset{bipoles/vsourceam/inner plus={\tiny $+$}}
\ctikzset{bipoles/vsourceam/inner minus={\tiny $-$}}
\ctikzset{logic ports=ieee}
\begin{document}
\centering
\begin{tikzpicture}[auto, node distance=4mm and 4mm,
                every node/.style={font=\tiny},
                >=latex,
                scale=0.7, % coordinates are 0.7cm apart
                baseline,
    ]
    \draw (0,0) to[C=$C$, -*] ++(1,0) coordinate(c-r)
        to[inline not, -*] ++(2,0) coordinate (not1-r)
        to[inline not] ++(2,0);
    % generator
    \draw (c-r) to[V=$V_{\mathrm{CM}}$] ++(0,-3);
    % feedback
    \draw (c-r) -- ++(0,1) coordinate(tmp)
        to[R] (tmp-|not1-r) -- (not1-r);
\end{tikzpicture}\quad
\ctikzset{resistors/scale=0.6, capacitors/scale=0.7,
    logic ports/scale=0.8, sources/scale=0.8}
\begin{tikzpicture}[auto, node distance=4mm and 4mm,
                every node/.style={font=\tiny},
                >=latex,
                scale=0.5, % coordinates are 0.5cm apart
                baseline,
    ]
    \draw (0,0) to[C=$C$, -*] ++(1,0) coordinate(c-r)
        to[inline not, -*] ++(2,0) coordinate (not1-r)
        to[inline not] ++(2,0);
    % generator
    \draw (c-r) to[V=$V_{\mathrm{CM}}$] ++(0,-3);
    % feedback
    \draw (c-r) -- ++(0,1) coordinate(tmp)
        to[R] (tmp-|not1-r) -- (not1-r);
\end{tikzpicture}
\end{document}

PS next time, please post an MWE that compiles in a standard distribution...