adding offset with an op-amp

[wizzo]

adding offset op

Need help:

i'm adding DC (4V) to an AC signal. Someone told me that operational amplifiers work well for that; i've been searching for the circuit but i can't find it. Can someone post the circuit, please? Any other suggestions for the same case will be welcomed as well.

 

[glenjoy]

op adding offset

Why add a signal (DC) on your AC, your signal will do nothing but ride on your DC signal.

 

[wizzo]

opamp add offset -low

to use an ADC next. Since my ADC do not accept negative inputs and the AC signal is +4 to -4 V, i add +4V to make it a +8 to 0 AC signal.

 

[AndrzejM]

add offset to ac signal

There are two inputs in operational amplifier.
If you apply your measured AC on "+" input of op. ampl.
You can add offset voltage to "-" input.
( Of course "+" voltage applied to "-" input shifts op. amp. output "negative".)
You should also take into accoout the amplifier gain.
(add 1 V offset if op ampl. gain = 4)
You insert this voltage not directly to "-" input of op. ampl. but between the GND and fedback resistor.