\begin{circuit}2

% Amplificador
\ov1 {} - {} {} {}

% entrada de v1 y v2
\atpin ov1+
\- 2 l \.3

% Conector de v1
\- 3 u \- 2 l
\nl \spring1 {$R_1$} l
\connection1 {$v_1$} c l

% Conector de v2
\atpin .3
\- 3 d \- 2 l
\nl \spring2 {$R_2$} l
\connection2 {$v_2$} c l

% Conector de salida
\atpin ov1O \.1
\connection3 {$v_o$} c r

% resistor 3
\atpin ov1-
\- 3 d \.2
\- 4 r

\nl \spring3 {$R_3$} r
\htopin ov1O
\vtopin .1

% Cables al otro resistor
\atpin .2
\- 1 d

% resistor 4
\cc\nl \spring4 {$R_4$} d

% Tierra
\gnd1

\end{circuit}