Summing non inverting op amp.

Jun 27, 2006 2 Replies

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



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

do you need a virual earth or summing amp?

huh?

Your description of the problem seems to call for something like this. |\ in------------|+`\ | >---+------>

.--|-,/ | | |/ | | | 4V--[110K]-+---[330K]-+ Bye. Jasen

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