I have a circuit which has a varying input. The circuit produces an output voltage proportional to the input. The output voltage varies from 0.4vdc to 8.6vdc. I need to add between 0.1vdc and 0.5vdc to the output voltage. I think an op-amp based summer can do the job, but I am not sure. The available supply voltage 13.2vdc to 14.5vdc. Any thoughts on how to build a analog summer? Also, any thoughts on how to generate the 0.1vdc to 0.5vdc signal from the supply voltage?

Thanks
GregQ

 

Look at the AD633 - www.analog.com/static/imported-files/Data_Sheets/AD633.pdf

Your low voltage can come from a resistive divider, but you will need to stabilize the supply voltage. Something like an LT1004 would do nicely - http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1002,C1223,P1209

 

A simple op amp wired as a summing amplifier can do the job.

To obtain a voltage between 0.1V and 0.5V use a pot with two resistors in series with it (one between it and ground and the other between it and Vcc) as to set the limits. You can put a capacitor between ground and the wiper to smooth out any noise voltage from the supply.