Hello everyone. I have been able to get back to my project again the last week. I have been struggling with the same problem for many days and I have finally run out of things to try.
I am trying to feed my Op-Amp Voltage Inverter with a Potential divider but with no accuracy.
The Potential Divider. - With a supply of 5 volts Point A gives me a ratio of 1:4 and correctly gives me 1.25volts.
The Op-Amp Inverter - If I supply say + 2 volts directly at point X from a power supply rail point Z correctly gives me - 2 volts. This is due to the fact that
Z (volts out) = - R4 / R3 x X (volts in)
so the real numbers are
- 1 / 1 x 2 = - 2
So far so good.
If I connect point A to Point X I do not see - 1.25v at point Z. I see -0.63 volts
If I remove R3 and replace R4 with a 3.9k resistor so that the Op-Amp maths looks correct I still do not see 1.25v at point Z. I see -5.02 volts
I have come back to this several times but I am stuck. I know that I am obviously missing fundamental knowledge here. Any and all help is very welcome.
Thanks kindly Paul.
I am trying to feed my Op-Amp Voltage Inverter with a Potential divider but with no accuracy.
The Potential Divider. - With a supply of 5 volts Point A gives me a ratio of 1:4 and correctly gives me 1.25volts.
The Op-Amp Inverter - If I supply say + 2 volts directly at point X from a power supply rail point Z correctly gives me - 2 volts. This is due to the fact that
Z (volts out) = - R4 / R3 x X (volts in)
so the real numbers are
- 1 / 1 x 2 = - 2
So far so good.
If I connect point A to Point X I do not see - 1.25v at point Z. I see -0.63 volts
If I remove R3 and replace R4 with a 3.9k resistor so that the Op-Amp maths looks correct I still do not see 1.25v at point Z. I see -5.02 volts
I have come back to this several times but I am stuck. I know that I am obviously missing fundamental knowledge here. Any and all help is very welcome.
Thanks kindly Paul.