DescriptionR2r-ladder.png	English: n bits R2R Lader
Date	10 April 2010
Source	Own work
Author	Lsibilla
Permission (Reusing this file)	This file is licensed under the Creative Commons Attribution-Share Alike 2.0 Belgium licence. You are free: to share – to copy, distribute and transmit the work to remix – to adapt the work Under the following conditions: attribution – You must give appropriate credit, provide a link to the licence, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible licence as the original. https://creativecommons.org/licenses/by-sa/2.0/be/deed.enCC BY-SA 2.0 beCreative Commons Attribution-Share Alike 2.0 betruetrue
Other versions	English .png English .png Russian .svg English .png

\begin{circuitikz}[scale=0.9]
    \def\n{2}

    \node (ground) at (-2, 0) {};
    \node (Vcc) at (0, 3) {};

    \foreach \contact in {0,...,\n}
    {
        % Define contacts for each bits
        \node (up contact \contact)    at ($({2*\contact}, 2)$) {};
        \node (down contact \contact)  at ($({2*\contact}, 0)$) {};

        % Draw R resistors and manage the a_{n-0} case
        \ifnum \contact>0

            \node (up contact -\contact)   at ($({2+4*\n-2*\contact}, 2)$) {};
            \node (down contact -\contact) at ($({2+4*\n-2*\contact}, 0)$) {};

            \draw (down contact \contact) to [R=R, *-*] ($(down contact \contact)-(2, 0)$);
            \draw (up contact -\contact) node[anchor=south] {$a_{n-\contact}$};
            \draw (down contact -\contact)   to [R=2R, *-o]  (up contact -\contact);
        \fi
        \ifnum \contact>1
            \draw ($(down contact -\contact)+(2, 0)$) to [R=R, *-*] (down contact -\contact);
        \fi

        % Draw 2R resistors
        \draw (down contact \contact)    to [R=2R, *-o]  (up contact \contact)
                                         node[anchor=south] {$a_{\contact}$};
    }
    
    % Draw ground and Vout
    \draw (down contact 0)  to [R=2R, *-*] (ground) node[ground] {}
          (down contact -1) to [short, *-o] ($(down contact -1)+(1,0)$)
                            node[anchor=west]  {$V_{out}$};

    % Draw ldots
    \draw[fill=black,decorate,decoration={shape backgrounds,shape=circle,shape size=1mm}]
                    ($0.67*(down contact \n)+0.33*(down contact -\n)$) -- ($0.33*(down contact \n)+0.67*(down contact -\n)$);
    \draw[fill=black,decorate,decoration={shape backgrounds,shape=circle,shape size=1mm}]
                    ($0.67*(up contact \n)+0.33*(up contact -\n)$) -- ($0.33*(up contact \n)+0.67*(up contact -\n)$);
\end{circuitikz}

Without the added declaration, pgf complained about shape size in the \draw statements.

\usepackage[symbols]{circuitikz}
\usetikzlibrary{decorations.shapes}