Add labels on circuits using tikz

Question

1. Can I add a label on the top line with the name "vdd"?
2. A value for the current source?
3. The name of the transistor on the emitter line and add a number of devices where "Q_1" is?

.

\begin{figure}[]
    \centering
    \begin{circuitikz}[american,node distance = 30pt]
    \draw (0,0) node[ground]{} to[Tpnp,name=Q1,l=$Q1$]
       ++(0,2) to[short]
       ++(0,2) node(v1){} to[I,invert,l^=$i_0$]
       ++(0,2)node[tground]{};    
    \draw (Q1.B) |- (0,0);
    \draw (v1) to[short] ++(1,0)node[below]{$v_D$} to[open,o-o]; 
    \end{circuitikz}
 \caption{The CTAT}
 \label{fig:CTAT}
 \end{figure}

Answer 1

You have a couple of problems here (and an error in the last line; you need a coordinate after a to and you have none).

The labels on BJT, as explained on the manual, are quite pesky (I do not change them for backward compatibility) and it's better to put them by hand.

I suppose you want something like this:

\documentclass[border=10pt]{standalone}
\usepackage[siunitx, RPvoltages]{circuitikz}
\begin{document}
\begin{circuitikz}[american,node distance = 30pt]
    \draw (0,0) node[ground]{} to[Tpnp,name=Q1]
       ++(0,2) to[short]
       ++(0,2) node(v1){} to[I,invert,l^=$i_0$]
       ++(0,2)node[tground](T){};
    \draw (Q1.B) |- (0,0);
    \draw (v1) to[short, -o] ++(1,0) node[below]{$v_D$};
    \path (Q1.east) node[right]{$Q_1$}; 
    \path (T.north) node[above]{$V_{dd}$}; 
    \end{circuitikz}
\end{document}