Diodes
$$ % Diode \begin{circuitikz}[scale = 1] \draw (0,0) todiode, i^>=$i_D$, v_<=$v_{AK}$ ; \end{circuitikz} $$
Common Cathode Diodes If two or more diodes are connected with a common cathode, the closed diode is the one with the most positive anode voltage. The rest of the diodes are open.
$$ % Common Cathode Diodes, by Diego Trapero \begin{circuitikz} \draw (0,0) tobattery1 (0,1) todiode (1,0) tobattery1 (1,1) todiode (2,0) toR (0,0) -- (2,0) (0,2) -- (2,2) ; \end{circuitikz} $$
Common Anode Diodes If two or more diodes are connected with a common anode, the closed diode is the one with the most negative anode voltage. The rest of the diodes are open.
$$ % Common Anode Diodes, by Diego Trapero \begin{circuitikz} \draw (0,0) todiode (0,1) tobattery1 (1,0) todiode (1,1) tobattery1 (2,0) toR (0,0) -- (2,0) (0,2) -- (2,2) ; \end{circuitikz} $$
\tabulinesep=1mm \begin{longtabu} to\linewidth{X[1,m,c]X[1,m,c]X[1,m,c]}
\hline
Configuration & Circuit diagram & Conducting Diode \\
\hline
Common Cathode
&
$$ % Common Cathode Diodes, by Diego Trapero
\begin{circuitikz}
\draw
(0,0) to[battery1](0,1)
(0,1) to[diode](0,2)
(1,0) to[battery1](1,1)
(1,1) to[diode](1,2)
(2,0) to[R](2,2)
(0,0) -- (2,0)
(0,2) -- (2,2)
;
\end{circuitikz}
$$
&
The diode with the most positive anode voltage
\\
\hline
Common Anode
&
$$ % Common Anode Diodes, by Diego Trapero
\begin{circuitikz}
\draw
(0,0) to[diode](0,1)
(0,1) to[battery1](0,2)
(1,0) to[diode](1,1)
(1,1) to[battery1](1,2)
(2,0) to[R](2,2)
(0,0) -- (2,0)
(0,2) -- (2,2)
;
\end{circuitikz}
$$
&
The diode with the most negative cathode voltage
\\
\hline
\end{longtabu}
General rule: The most polarized diode is the one conducting. The one with the biggest