LPF (Low Pass Filter) block

Question

I am trying to generate a LPF block with TikZ.

I have found out the option of drawing a LPF with CircuiTikZ:

\documentclass[border=10pt]{standalone}  
\usepackage{tikz}
\usetikzlibrary{shapes,arrows,positioning}
\usetikzlibrary{arrows.meta}
\usepackage{circuitikz}

\tikzset{
block/.style = {draw, fill=white, rectangle, minimum height=3em, minimum width=3em},
tmp/.style  = {coordinate}, 
input/.style = {coordinate},
output/.style= {coordinate},
pinstyle/.style = {pin edge={to-,thin,black}
}
}

\begin{document}  

    \begin{tikzpicture}
        \node [input, name=input] {};
        \node [block, right=20mm of input] (A) {A};
        \node [block, right=20mm of A] (B) {B};
        \draw [-{Latex[length=2mm]}] (A) to[lowpass](B);
    \end{tikzpicture}

\end{document}

This has 2 problems:

1. The line connecting blocks goes through them, and does not start at their edge.
2. There is no arrow pointing towards the LPF

I have unsuccessfully tried to find a workaround to this.

Is there any way I could make it look like this?

(As a last request, is it also possible to make the border of the block have the same thickness as A and B?)

Answer 1

\documentclass[tikz, margin=3mm]{standalone}
\usetikzlibrary{arrows.meta, positioning}
\usepackage{circuitikz}

\begin{document}
\begin{tikzpicture}[box/.style={draw, thick, minimum size=10mm}]
    \node [box] (A) {A};
    \node [box, right=20mm of A] (B) {B};
    \path (A) to [lowpass, name=lpf] (B);
    \draw [-{Latex[length=2mm]}] (A.east) to (lpf.west);
    \draw [-{Latex[length=2mm]}] (lpf.east) to (B.west);
\end{tikzpicture}
\end{document}

edit: if you like change lowpass border thickness, than you only need redefine bipoles thickness:

\ctikzset{bipoles/thickness=1}

and above image you can redraw in:

complete mwe is:

\documentclass[margin=3mm]{standalone}
\usepackage{circuitikz}
\usetikzlibrary{arrows.meta, positioning}

\begin{document}
    \begin{tikzpicture}[
    box/.style = {draw, inner sep=2pt, minimum size=10mm},
     LA/.style = {-{Latex[length=2mm]}},
 node distance = 22mm
                ]
\ctikzset{bipoles/thickness=1}
%
\node [box] (A) {A};
\node [box, right=of A] (B) {B};
\path (A) to [lowpass, name=lpf] (B);
\draw [LA] (A) to (lpf.west);
\draw [LA] (lpf.east) to (B);
    \end{tikzpicture}
\end{document}

Answer 2

It is also possible to not use path objects, but use them as nodes. I found this helpful in mixed graphs that are not pure circuit or block diagrams. Most of the path objects do have corresponding shapes for the node, usually accessible by appending shape to the name.

In the example below this is lowpassshape

MWE:

\documentclass[margin=3mm]{standalone}
\usepackage{circuitikz}
\usetikzlibrary{arrows.meta, positioning}

\begin{document}
  \begin{tikzpicture}[
    box/.style = {draw, inner sep=2pt, minimum size=10mm},
    LA/.style = {-{Latex[length=2mm]}},
    node distance = 22mm
                    ]
    \ctikzset{bipoles/thickness=1}
    %
    \node [box] (A) {A};
    \node [lowpassshape, right=of A] (lpf) {};
    \node [box, right=of lpf] (B) {B};
    \draw [LA] (A) to (lpf.west);
    \draw [LA] (lpf.east) to (B);
  \end{tikzpicture}
\end{document}