# Can't balance differential amplifier circuit

I'm trying to build a circuit which involves an Op Amp in differential amplifier configuration. However I've been having difficulty balancing my output. My understanding of the differential amplifier is that if configured such that R1 = R2 = Rf = Rg then Vout should be about 0 volts except I'm always getting about 0.5-0.8 volts.

I've currently set it up so that there are 5 volts going directly into R1 and R2 with all my resistors equal to 10K ohms and still I'm getting about 0.63 volts. These are diagrams of my circuit I made:

Please also ignore the dashed lines.

This is what I was trying to build:

Edit: Original Circuit

• I suspect you're seeing inaccuracies in your resistor values. EDIT: never mind, that wouldn't be this significant. @stowoda has the right idea. Oct 30, 2018 at 11:01
• The Opamp will not go to 0 V if you have an unsymmetrical supply. Keep that in mind. There is also some offset error in an ideal Opamp. Oct 30, 2018 at 11:02
• I've checked and re-checked the resistor values using a bridge (same voltage drops) and I'm not sure what you mean by unsymmetrical supply (R1 and R2 receive 5V each) Oct 30, 2018 at 11:04
• You are supplying the Opamp with +5 V. This is unsymmetrical. If you would supply it with -5 V to + 5 V that would be called symmetrical. Another hint to what I have stated above: Figure 11 (Output Characteristics Current Sinking). Have a look for that in the Opamp's datasheet (I guess yours is LM358) Oct 30, 2018 at 11:10
• Should I invert one of the inputs via another Op Amp configuration? Oct 30, 2018 at 11:18