Electronic – OrCAD doesn’t yields same result for this difference amplifier

operational-amplifierorcadpspice

The question says:

Design an op amp circuit with inputs \$v_1\$ and \$v_2\$ such that
\$v_o = 3v_2-5v_1\$

One way to realize this circuit is to utilize difference amplifier which satisfies this equation
$$
v_o = \frac{R_2(1+R_1/R_2)}{R_1(1+R_3/R_4)} v_2 – \frac{R_2}{R_1}v_1
$$

for this circuit
enter image description here

Unequivocally, \$\dfrac{R_2}{R_1}=5,\ \ \dfrac{R_2(1+R_1/R_2)}{R_1(1+R_3/R_4)} =3 \implies R_2=5R_1, R_3=R_4\$. If \$ v_1=6, v_2=2 \implies v_o=3v_2-5v_1=3(2)-5(6)=-24\$. Using PSpice to realize this circuit, I'm getting different result

enter image description here

Best Answer

enter image description here

With the input voltages present, the output would need to be -24 volts but, it's likely that the power rails applied in OrCAD are limiting the output to +/- 15 volts hence, you get negative clipping.

Try inputting 0.6 volts and 0.2 volts to get -2.4 volts on the output.