How do you add dc voltage to ac signal. I know how to get rid of it just use a capacitor. For example you have a 2.5 sin(400000*pi*t) input signal then i want to add a 2.5 volts to it using an op amp. the vcc and vee is 5 volts for the op amp i need a circuit to do this. thanks

 

Run the AC signal into the inverting input through a resistor. Have the feedback resistor the same size for 1:1 operation - something like 20K is a reasonable value. Use a trim pot to add the offset to the non-inverting pin. The output will have the AC signal running on the DC offset.

 

what is a trim pot?

 

my out put really shrink. i dont know y

 

A trim pot (actually potentiometer) is a small variable resistor. Also called a "trimmer".

 

You could also use a capacitor and an inductor. The AC input will be through the cap and the DC input will be through the inductor.

It is an easy trick to use in a lab environment. Look up 'Bias Tee.'

 

i dont know y the signal became .002sin(400000*pi*t)+4.882

 

What does your op-amp circuit look like? A schematic would be nice. Looks like your are pegging one of the rails.