Hi,
i need a differential amplifier with a very accurate gain of 2 at a frequency of 50 kHz (1.9999<gain<2). When assuming ideal resistors, my calculation leads to opamps with a GBP greater than 15 MHz. For a test i chose the LM833, even though its minimum GBP is too small. I have attached an Image of the acutal test board along with a simple schematic.
The circuit behaves in a way i did not expect. At 50 kHz the gain is too big. Its round about 2.04 instead of 2.
The resistors are high precision and a measurement with a preciscion impedance analyser results in the correct resistances.
At low frequencies (<10kHz) the gain is much closer to 2.
At frequencies above 50 kHz the gain rises even further and than falls at about 150 khz.
I would expect the frequency response to be much more flat and the amplifier to be much more accurate at 50 kHz.
Any help would be greatly appreciated!
Kind regards,
Markus Schyma