I made a schematic using following code:
\begin{circuitikz}
\draw
(0,0) node[op amp, scale=2] (opamp) {}
(opamp.+) -- (-2.38,-3) node[ground] {}
(opamp.+) node[left, above] {$u_+$}
(opamp.-) node[left, below] {$u_-$}
(opamp.out) to[short, -*](4,0) node[right] {$u_{izl}$}
(opamp.-) to[R, label=$R_1$, i<=$i_1$, *-*] (-8, 1) node[left] {$u_{ul}$}
(opamp.-) to[short] (-2.4,4) {}
(-2.4, 4) to[R, label=$R_2$, i>=$i_2$] (3,4) {}
(3,4) to[short, -*] (3,0)
(opamp.up) to[short, -*] (-0.17,2.5) {}
(opamp.down) to[short, -*] (-0.17,-2.5) {}
(4,0) to[] (4,0) {}
;
\end{circuitikz}
However some of the lines on it aren't straight like these ones:
I tried changing coordinates but I can't get it right. Is there an easier way of doing this?