[Tex/LaTex] Aligned circle around letter – tikz

Question

I am using the following tikz-based command to create a circle around a letter.

\newcommand*\circled[1]{\tikz[baseline=(char.base)]{
        \node[shape=circle,draw,minimum size=4mm, inner sep=0pt] (char)
        {#1};}}

It works fine, but whenever I use multiple letters in the same line, they are not aligned.

I guess it has something to do with the baseline, like the circle is created in reference to the center of mass. Notice that b and d are a bit higher than a and c. How could I fix that?

UPDATE

Following the advice I got from the comments (thank you all), I got the circles aligned to each other (which is what I wanted), but unfortunately not to the text:

I saw the other post proposing this propnode (the pink a), and I tried to shift it all over the place using the first argument, but it had no effect.

\pgfmathsetmacro{\nodebasesize}{1} % A node with a value of one will have this diameter
\pgfmathsetmacro{\nodeinnersep}{0.05}
\newcommand{\propnode}[5]{% position, name, options, value, label
\begin{tikzpicture}
    \pgfmathsetmacro{\minimalwidth}{sqrt(#4*\nodebasesize)}
    \node[#3,minimum width=\minimalwidth*1cm,inner sep=\nodeinnersep*1cm,circle,draw] (#2) at (#1) {#5};
    \end{tikzpicture}
}

In fact, propnode is a bit too high and circled is a bit too low. This is the code which calls everything:

(\circled{b},\circled{a},\circled{c},\circled{d},\propnode{0,4}{n05}{fill=pink,text=black}{0.15}{a}). 

Answer 1

Here's an example using a strut:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\newcommand*\circled[1]{\tikz[baseline=(char.base)]{
        \node[shape=circle,draw,minimum size=4mm, inner sep=0pt] (char)
        {\rule[-3pt]{0pt}{\dimexpr2ex+2pt}#1};}}


\begin{document}

\foreach \myn [count=\myc] in {a,b,c,d,e,p,q}
{%%
  \circled{\myn}\ifnum\myc<7\relax,\fi
}%%

\end{document}