Why do the input channels on my TLA float to 2.2 volts?

The  P6410,  P6417, P6418 and P6434 probes have probe loading characteristics of 20kohm to 2.2V*. This is why the signal may be pulled to to 2.2V around the signal transitions. An optional Reduced Bias Voltage lead set (part number 196-3477-00 for 8 channel leadset and 196-3478-00 for single channel leadset)  can reduce the pull-up voltage that the probe delivers to the system under test down to 1.1V. This will also change the DC input resistance from 20kohm to 10kohm. Another option is the TLAHRA which has a 10Mohm input impedance and works with existing P6417, P6418, and P6810 probes.

*The TLA5000  and TLA5000B  series sees a probe loading of 20k to 0V.