Summing non inverting op amp.

[daveatfernie]

Hi,
I've a voltage change 3-4 Volts which I need to change into a 0 to 4
Volt signal.
I have used an inverting op-amp with a virtual ground to give a
cracking result but unfortunately the voltage is going the wrong way
(decreasing instead of increasing.

I have changed to circuit over to be a non inverting amplifier but I'm
worried about the virtual ground. I've been told that summing in a non
inverting op amp can be difficult.
I took the series resistors out of the circuit from my virtual ground
(created from a pot) and from the voltage that I'm amplifying. I have
a 560K feedback and 220K to ground giving me a gain of around 3.5.

Will I have problems with the virtual ground being amplified to or any
other problems?

Many thanks in advance.

David

 

[daveatfernie]

If I was to conect my ground resistor to my virtual ground would this
be a better circuit. I'm now worried that my offset voltage from the
virtual ground will also be amplified by the op amp.

Cheers again

David