I report the results of the measurement to know how offset voltage of common mode servo changes when the gain is changed.
- Motivation: If discontinuous change of the offset happens when we change the gain, it could cause saturation somewhere and so make the length control down. So, we want to estimate effect of such discontinuous change.
- Method: In 1 (or In 2) was terminated with 50 ohm, and the output voltage at Out 2 was measured with a multimeter (D040180-B).
- Results are shown below. Acquired data are attached in .zip.
The upper shows input equiv. offset. The lower shows offset measured at Out 2.
As for both In1 and In2, strange behaviors can be seen between -17 dB and -16 dB.
This is because 5 amplifiers (or attenuators) are simultaneously enabled/disabled here. Similar situation occurs every change of 8 dB gain.