Ground alignment in my circuit

I would draw the circuit in the following way, writing it left-to-right as I feel it's more natural. So, I'll start with

draw (0,0)  node[above]{D11} to[R=SI{15}{kohm}, o-] ++(3,0) coordinate(corner-in)
        to [R=SI{10}{kohm}] ++(0,-3) % this -3 will fix the gnd line
        node[tlground](GND){};

Now let's position the opamp and connect it to GND:

draw (corner-in) -- ++(1,0) node[en amp, anchor=+](opamp){texttt{LM358}}
        (opamp.down) -- (opamp.down|-GND) node[tlground]{};

Now, I feel that the standard position of the inputs in en amps is a bit cramped. A quick glance at the manual tells me that the solution is ctikzset{tripoles/en amp/input height=0.45}; I'll put that in the preamble (full code later).

The next step is to close the buffer feedback loop and to add the power supply. I advise against using the crossing thing, but if you want to, a solution could be:

     draw (opamp.up) to[crossing, name=X] ++(0,1) node[vcc]{SI{5}{V}};
     draw (opamp.-) |- (X.center) -| (opamp.out);

Notice how I give a name to the crossing and then use the X.center anchor to draw the line --- so now I can change the ++(0,1) over there and anything will fall back in place. |- and -| are very handy TikZ shortcuts.

Let's finish now the circuit with the load resistance and the indication of the output voltage. At this point I decided to change the tlground for ground to have the little tail, and to move the ground level higher --- notice that this is just a change in one number and a search-and-replace for tlground to ground. The final code is

documentclass[border=2mm]{standalone}
usepackage[european, RPvoltages, siunitx, straightvoltages]{circuitikz}
ctikzset{tripoles/en amp/input height=0.45}
begin{document}
    begin{circuitikz}
        draw (0,0)  node[above]{D11} to[R=SI{15}{kohm}, o-] ++(3,0) coordinate(corner-in)
        to [R=SI{10}{kohm}] ++(0,-2) % this -2 will fix the gnd line
        node[ground](GND){};
        draw (corner-in) -- ++(1,0) node[en amp, anchor=+](opamp){texttt{LM358}}
        (opamp.down) -- (opamp.down|-GND) node[ground]{};
        draw (opamp.up) to[crossing, name=X] ++(0,1) node[vcc]{SI{5}{V}};
        draw (opamp.-) |- (X.center) -| (opamp.out);
        draw (opamp.out) -- ++(0.5,0) coordinate(rload)
        to[short, -o] ++(1.5,0) coordinate(out) node[above]{A1};
        draw (rload) to[R=SI{1}{kohm}] (rload|-GND) node[ground]{};
        draw (out) to[open, v^=$V_s$] (out|-GND) node[ground]{};
    end{circuitikz}
end{document}

Notice that the last screenshot is done with evince, and the previous ones with okular, which has a strange idea of antialiasinging lines...

And finally, what really got me started with circuitikz, is that now, with a trivial change (just change en amp to op amp, raise a bit the vcc — just one number change again! — and add ctikzsetstyle{romano} somewhere after loading the package) and you have

And a final note: the only absolute coordinate is the (0,0) at the start. Move this and the circuit will follow; this is great to create duplicates, for example, or to create basic blocks that you can reuse around (I normally create macros for them).