A bi-directional interface circuit includes a transmitter portion, a receiver portion, a current source bias circuit, and a switch. When the interface circuit is transmitting data, the switch steers the bias current generated by the current source bias circuit to the transmitter portion of the interface. When the interface is receiving data, the switch steers the bias current to the receiver portion of the interface. Thus, the current-source bias circuit is kept on regardless of whether the interface is transmitting or receiving data. Because the current-source bias circuit is not turned on and off, the switching noise generated when the interface transitions between transmitting and receiving operations is eliminated or reduced. Consequently, any dead time inserted for such a transition can be minimized, and the effective bandwidth of the interface is increased.