AC couple amplifier output

[col_implant]

Hi,

I have a sinewave signal which my generator outputs, it ranges between 500Hz and 10kHz. It is about 600mV in amplitude (pk-pk) with an offset of about 1.2V. I want to convert this into an AC coupled signal of 2V pk-pk. So I have use a simple inverting amplifier configuration with a capacitor in series with the input resistor to 'block' the DC offset.

I still see a positive offset in my output signal, so I added a lowpass RC filter. Now I am seeing a negative offset at the output of the RC filter.

If I AC couple my input should my output not automatically be AC coupled???

Also how is the DC bias getting through my output RC filter.

Maybe I'm going about this totally the wrong way, any advice greatly appreciated.

Thanks

C

 

[ericgibbs]

Hi,

I have a sinewave signal which my generator outputs, it ranges between 500Hz and 10kHz. It is about 600mV in amplitude (pk-pk) with an offset of about 1.2V. I want to convert this into an AC coupled signal of 2V pk-pk. So I have use a simple inverting amplifier configuration with a capacitor in series with the input resistor to 'block' the DC offset.

I still see a positive offset in my output signal, so I added a lowpass RC filter. Now I am seeing a negative offset at the output of the RC filter.

If I AC couple my input should my output not automatically be AC coupled???

Also how is the DC bias getting through my output RC filter.

Maybe I'm going about this totally the wrong way, any advice greatly appreciated.

Thanks

C

hi,
I assume you are using dual power supplies to the OPA.?

Post your circuit and we can help sort it.

 

[BrownOut]

Amplifiers often have a built-in output offset. Why not just capacitively couple the output?

 

[electronspeed]

Generally amplifiers have some offset voltage.To prevent this say in 741 we go for compensation resistors.But any way capacitor should block dc signal.Impedance coupling seem to work but strength of your ac signal raises doubts.