I'm drawing an equivalent circuit of a Triode (Vacuum Tube) using circuitikz. Here is my code:

\ctikzset{tubes/width=2.8, tubes/height=4, tubes/fill=cyan, tubes/thickness=4}
\ctikzset{resistors/scale=1.1, inductors/scale=1.2}
 \draw (0,0) node (start) {}
  to[L=$L_g$,o-] ++(2,0) to[R=$R_g$] ++(4,0)
  node[triode,anchor=control] (Tri) {} ++(2,0)
  (Tri.cathode) to[R=$R_c$,-] (Tri.cathode |- start) to[L=$L_c$,-o] ++(0,-2)
  (Tri.anode) to[R=$R_a$] ++(0,4) to [L=$L_a$,-o] ++(0,2);

Now I'd like to draw parasitic capacitors with "curved/rounded" terminals. e.g. like this: Equivalent circuit vacuum tube - Triode Is it possibile using circuitikz? Any idea?

1 Answer 1


Really there is no provision for elements on curved paths in circuitikz, but you can use the node form of the capacitor and do a bit of manual fiddling. If you add at the end of your snippet:

  \coordinate (a) at ([xshift=-0.5cm]Tri.control);
  \coordinate (b) at ([yshift=0.5cm]Tri.anode);
  \coordinate (c) at ([xshift=.7cm, yshift=-.7cm]a|-b);
  \node [capacitorshape, rotate=45](C1)  at (c){};
  \draw (a) to[out=90, in=225] (C1.left) (C1.right) to[out=45, in=180] (b);
  \path (C1.center) ++(-0.6,0.6) node{$C_\mathit{ga}$};

you'll obtain:

enter image description here

...the rest of the parasite capacitances is left to the reader... ;-)

  • Really useful! [SOLVED]
    – mikilinux
    Feb 12, 2020 at 21:49

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