\begin{circuit}1

\at 0 0 \P1
\nl\cc \U1 {$v_1$} - d
\- 2 d \P2
\nl\cc \U2 {$v_2$} - d
\- 2 d \P3

\atpin P1 \shift 0.5 -0.8
\put{$+$}

\atpin P2 \shift 0.5 1.8
\put{$-$}


\atpin P2 \shift 0.5 -0.8
\put{$+$}

\atpin P3 \shift 0.5 1.8
\put{$-$}


\end{circuit}