I have a question that OpAmp looks like Summing but there are Voltage applied to the + input.

note that there are 2 input voltage 150mV and -153mV to the 741 OpAmp, i know the calculation of Summing Amplifier and the value shud be 0.28V, but when connect a 0.5V to the + input, it bcome looks like differential but without Rf and Ri, and the output become 3.188V, can someone show me the formula for getting 3.188V?

 

The gain of the opamp for signals applied to the + input is 5.8. When you mulitply 0.5 times 5.8 you get 2.9V. The balance of the output signal is accounted for by the other two voltage inputs and their associated gains.

In summary, the simulated opamp is operating correctly.

hgmjr

 

If you make the analysis of the circuit you get this equation:

Vo=(-V1+0.5)*R5/R6+(-V2+0.5)*R5/R3+0.5

Plug the numbers in and you get the answer the simulation gave you.

 

If you make the analysis of the circuit you get this equation:

Vo=(-V1+0.5)*R5/R6+(-V2+0.5)*R5/R3+0.5

Plug the numbers in and you get the answer the simulation gave you.

\(V_{O}\,=\,(0.5-V_4)\,*\,{\Large \frac{R5}{R6}}\,+\,(0.5-V_8)\,*\,{\Large \frac{R5}{R3}}\,+\,0.5\)

The above equation is the same as mik3 using the LaTex format.

hgmjr