I am attempting to build a circuit that excites a sensor which requires an AC current of ±1mA and 20kHz frequency. For this, I used voltage to current converter integrated circuit XTR110, which is controlled by a sine wave generator. However, this IC can only produce a positive current, so the output is AC current with DC offset. To ensure that the sensor is excited only by ±1mA current, I added an inductor of 39mH between the output terminals of IC and a capacitor of 100nF in series with the sensor to completely remove the DC offset as shown in the schema.
The sensor is represented by the R_Loud in the schema. I got an AC current with no DC offset flowing through the R_Loud. However, the peak to peak of the AC current is affected by the resistance of the R_Loud. In other words, when the resistance of the R_Loud increases, the AC current reduces.
is there another way to remove the DC offset and ensure a stable AC current?!
Or, is there another integrated circuit that can provide a negative current as well?!
Note: I'm not an electrical engineering specialist
Best Answer
It seems the inductor is creating a parallel load with your resistor + capacitor. This means that the current will be split between the two.
You can remove the inductor and use a big capacitor to couple the AC component only.
You’re also shorting the dc component to ground with an inductor, which is a bad idea