I'm working on a waveform generator for which I'm using the DDS AD9833 chip to generate sine signals and triangular signals. I'm trying to amplify these waves since the AD9833 output is 600mVpp and I need waves up to 10 Vpp. The problem is to amplify these waves without the insertion of harmonics; to do this, I wanted to use the INA129 instrumentation amplifier but, by using a common potentiometer, everything went well, but the gain has to be controlled by a microcontroller, so I wanted to use the TPL0102 digital potentiometer.
The potentiometer works well on its own, but when I connect it as the resistance gain of the INA129, the output is always saturated, even when I set the minimum gain, which is 1.
- INA129 powered with +/- 11V
- INA 129 V- input connected to AGND
- AD9833's output connected to high pass filter to remoce DC voltage, then, it is connected to the V+ pin of the INA129
- TPL0102 Vss pin connected to DGND
- AGND and DGND connected through a 1MΩ resistor
- TPL0102 controlled through I2C with Atmega 328 microcontroller
How can I correct this problem?