What termination model (Balanced vs. Unbalanced) should I use for my M8000 BERT?

For M8000 (M8041A/51A/61A/62A) BERT data outputs, a Termination Model must be selected in the Amplifier section of the Parameters window, Balanced or Unbalanced. This setting is one factor which determines when the output protection circuits are engaged and the outputs turned off.

Unbalanced means that the DUT's resistor is connected to a termination voltage. In the unbalanced case, the DC voltage depends on the DUT's termination voltage as well as the BERT's output amplifier. One common example of an unbalanced termination model is when connecting the data outputs to the input channels of a scope or DCA. The oscilloscope inputs are terminated with 50 Ohms to 0 V (GND).

Balanced means that the DUT has a 100 Ohm differential termination between normal and complement. This is a floating termination, and the DC voltage on the line is only determined by the BERT's output amplifier.

It is because of the DC voltage difference that the output protection circuits needs to distinguish between the two cases.