An apparatus and system are provided to adjust an output voltage of an integrated circuit (IC) die. For instance, the apparatus can include an on-chip source termination and a bias generator. The bias generator can be configured to provide a source current to the on-chip source termination to adjust the output voltage. In particular, when adjusting the output voltage of the IC die, the bias generator can adjust the source current using a first current with a first adjustable current gain and a second current source with a second adjustable current gain.