My op amp doesn't work well under AC input

[athrun200]

The type of op amp I am using is Voltage-to-Current Amp.

Under DC voltage input, it works perfectly well, boosting the current of a signal generator (DC mode) up to 250mA with the help of single supply working at 25V.

However, when I turn the signal generator in AC mode, hoping to achieve AC current oscillating between the value of +125mA and -125mA by adjusting the offset, I found that the negative current won't decrease.

By decreasing the offset, the positive value keep decrease (from 250 to 200mA), but the negative one get stuck at -4mA.

When the offset is lowered to a certain value, the positive value suddenly drop to negative.

I have no idea what's going on. It is my first time to play with a op amp, I didn't expect it to be so complicated.

 

[davenn]

hi there

well let's start by you giving us the actual type of Op-Amp ( model #)
then let's get a circuit from you that you are working from
Then a photo or 2 of your actual made up circuit

Then some of us may be able to see if you have made an error either in your circuit or construction etc

cheers
Dave

 

[analogdesign]

Indeed, we don't even know what frequency you are operating at, or if you are slewing.

Analog circuits are a bottomless pit of complexity.

 

[Averagesupernova]

Analog circuits are a bottomless pit of complexity.

Well said!