--- /dev/null
+function n=DDGOXTelectron_driftdiffusion(mesh,Dsides,nin,pin,V,un,tn,tp,n0,p0,weight)
+
+%%
+% n=DDGelectron_driftdiffusion(mesh,Dsides,nin,pin,V,un,tn,tp,n0,p0,weight)
+%
+% IN:
+% V = electric potential
+% mesh = integration domain
+% nin = electron density in the past + initial guess
+% pin = hole density in the past
+% n0,p0 = equilibrium densities
+% tn,tp = carrier lifetimes
+% weight = BDF weights
+% un = mobility
+%
+% OUT:
+% n = updated electron density
+%
+%%
+
+% This file is part of
+%
+% SECS2D - A 2-D Drift--Diffusion Semiconductor Device Simulator
+% -------------------------------------------------------------------
+% Copyright (C) 2004-2006 Carlo de Falco
+%
+%
+%
+% SECS2D is free software; you can redistribute it and/or modify
+% it under the terms of the GNU General Public License as published by
+% the Free Software Foundation; either version 2 of the License, or
+% (at your option) any later version.
+%
+% SECS2D is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with SECS2D; If not, see <http://www.gnu.org/licenses/>.
+
+
+BDForder = length(weight)-1;
+
+
+
+denom = (tp*(nin(:,end)+sqrt(n0.*p0))+tn*(pin(:,end)+sqrt(n0.*p0)));
+M = weight(1) + pin(:,end)./denom;
+
+u = un;
+
+U = p0.*n0./denom;
+for ii=1:BDForder
+ U += -nin(:,end-ii)*weight(ii+1);
+end
+
+guess = nin(:,end);
+n = Udriftdiffusion(mesh,Dsides,guess,M,U,V,u);
+
+