# Transistors inconsistent anchors

The nmos and pmos transistors have different placements for their source and drain anchors (for nmos, drain is on top and source on bottom; for pmos, source is on top and drain is on bottom). Why is this?

\begin{circuitikz}
\draw (0,0) node[nmos](n){}
(n.gate) node[anchor=east]{G}
(n.drain) node[anchor=south]{D}
(n.source) node[anchor=north]{S}
%
(3,0) node[pmos](p){}
(p.gate) node[anchor=east]{G}
(p.drain) node[anchor=north]{D}
(p.source) node[anchor=south]{S};
\end{circuitikz}


• From Device Physics the function of Source and Drain are interchangeable. However, protection diodes may be applied asymmetrically, and are not shown, which make S and D less interchangeable. // From an electric perspective the hidden message is where to put plus and minus poles from the battery ... which depends on the MOS-transistor type used. From this perspective it's a conclusive definition. Jan 21 at 6:52