Diode is 1N4148

Resistor Value is 33Kohms

And the results in lab and simulating don't match the results using the following formula:

Vin= 6v

Vdd+=15v

Vdd-=-15v

Vt= 0.026 v

Is (Saturation Current = Reverse current) = 25 nA (I took from diode datasheet)

Even simulating results and lab results don't match.

Vin Simulating (Using multisim) ____Lab _____Formula

6v=> -0.552 _________________-0.523____ -0.231

5v=> -0.547 _________________ -0.516 ___ -0.226

4v=> -0.541 _________________-0.505_____-0.221

I don't know if I'm applying correctly the formula or if this is the formula I have to use.

Thank you very much in advance,