# Drawing a logical gate diagram with the circuitikz package

My goal is to have a diagram which looks like this:

I would like to accomplish this with the circuitikz-package. So far I have already written this piece of code:

\begin{circuitikz} \draw
(0,2) node[and port] (and) {}
(0,0) node[xor port] (xor) {}
(and.in 1) node[above left=.5cm](a) {$a_0$}
(and.in 2) node[below left = .5cm](b) {$b_0$}
(and.out) node[below](s) {$s_1$}
(xor.out) node[below](s) {$s_0$}
(a) -| (and.in 1)
(b) -| (and.in 2)
(a) -| (xor.in 1)
(b) -| (xor.in 2);
\end{circuitikz}


I would be more than happy, if you could help me to get the second image look more like the first one. Many thanks!

Edit: I just managed to get an image which is a bit better, by changing the position in the third line from (0,0) to (2,2)

Since this is just a dirty hack which dosn't scale to more complex diagrams, I would still appreciate help for a more general solution!

The main change is to have separate x coordinates for the vertical lines, changing e.g.

(a) -| (and.in 1)
(a) -| (xor.in 1)


to

(a) -- +(0.5,0) |- (and.in 1)
(a) -- +(0.5,0) |- (xor.in 1)


To make the circuit look even more like the sample circuit, one might want to move a_0 down.

\documentclass{article}
\usepackage{circuitikz}
\begin{document}
\begin{circuitikz} \draw
(0,2) node[and port] (and) {}
(0,0) node[xor port] (xor) {}
(and.in 1) node[below left=.5cm](a) {$a_0$}
(and.in 2) node[below left = .5cm](b) {$b_0$}
(and.out) node[below](s) {$s_1$}
(xor.out) node[below](s) {$s_0$}
(a) -- +(0.5,0) |- (and.in 1)
(b) -| (and.in 2)
(a) -- +(0.5,0) |- (xor.in 1)
(b) -| (xor.in 2);
\end{circuitikz}
\end{document}