LM358 strange output

[usbspy]

Hi guys,

I am simulating a simple differential amp with gain of 10.

The Vin- is 0.5v Vin+ is 0v

Output is 315mV.

From the equation output should be 0v.

Vo = A*(Vin+  - Vin-)

Positive supply is 12V and negative is 0v. (Single supply).

I cant figure out why the o/p is 315mV.

Multiim file attached.

[supsup]

Vo = A*(Vin+ - Vin-) = 10*(0 - 0.5) = -5V

For negative size of output voltage it is necessary a bipolar source for power supply.

[usbspy]

supsup, I understand the output should be -5v. The LM358 is a single supply opamp. output should be 0v.

My inputs are within the specified input range (even for single supply).

[supsup]

LM358 is not rail-to-rail amplifier. At single supply voltage output will be never equal to zero.

Use, for example, AD8571 ( single supply = 5V). Thus you receive voltage output approximately 1 mV.

[usbspy]

Well, the datasheet says Vout can goto ground.

In the specs, Vout is 20mV when V+ is 5V

I will try with AD8571 and see what happens.

[supsup]

Datasheet and model - different things. The model can be insufficiently precisely created. In the program there are some models LM358. If, for example, to use LM358M voltage output equal-4,98V, and it at power supply 12V cannot be.

[supsup]

If to use in your circuit model STMicroelectronics/LM358, voltage output will be equal 4mV.

[usbspy]

Well, you are right. I get -4.97v, 4mv and 56mV when I pick different variants of LM358.

How do I pick the correct model?

The one on the bread board is LM358P by TI. I do get 330mV when Vin- is higher than Vin+

In sim, when I use LM358P(by ST micro), I get an output of 56mV. The P version is not available from TI in simulation.

When I use the National/LM158_4, I get an output of 4mV.

[supsup]

I think that the correct model can be chosen only on the basis of practice. However, absolutely correct model, most likely, to find it will not turn out. You can try to create it, using model maker.