Analog calculations with IC

[Poptart]

Hi,

I've been having a bit of trouble finding a summer IC that can perform the following calculation:

V0 = V1 + V2 - (V3 + V4)

I found the LM324 which includes that calculation in its documentation, but it requires V1 + V2 > V3 + V4 since it's only got V+ and GND inputs. This requirement is a deal-breaker since my possible V0 can be either positive or negative.

In my circuit, V1-4 all can range from 0 to 100 mV. Does anyone know of a specific IC that would be able to meet these criteria?

Thanks for the help,
-Ben

[schip666!]

You can bias everything up by a known amount, or use pretty much any opamp made for dual supply operation. The good old 741, or any of the TL08x series come to mind.

[Bob S]

You will get the best results if you sum only on the inverting inputs. U3 in the thumbnail is a standard differential amplifier configuration.

Bob S