Patent ID: 7400170

Claim:
A differential current mode serial-bus driver circuit for the IEEE 1394 standard, comprising: a transmit driver for driving differential signals forming a differential signal pair in current loop signaling, the transmit driver comprising a pair of current steering switches operatively connected to a pair of current mirrors, further comprising, a first current mirror providing a positive current for said transmit driver to produce a positive differential voltage signal for the differential signal pair; and, a second current mirror providing a negative current for said transmit driver to produce a negative differential voltage signal for the differential signal pair, and a plurality of gate-biasing MOS transistors connected to bias the gates of the pair of current-steering switches, said first current steering switch comprising a pair of MOS transistors, and said second current steering switch comprising a pair of MOS transistors; voltage signals applied to the source of said current-steering switch MOS transistors; andwherein the voltages produced by said gate-biasing MOS transistors and said source voltage signals bias said first and second current steering switches into saturation mode; a first output for said positive differential voltage signal for the differential signal pair; a second output for said negative differential voltage signal for the differential signal pair; a pair of differential data inputs, having differential data input signals CP and CM, and a three-state control signal VTRI for DC signaling; a make-before-break circuit connection operatively connected to said current steering switches for allowing current from said first and second current mirrors to be switched between said first and second output in response to differential data input signals CP and CM; said transmit driver drives the differential signals in response to synchronized input waveforms, and, said pair of current steering switches comprises a first current steering switch comprised of transistors and a second current steering switch comprised of transistors; said transmit driver is supplied by supply voltages VDDA and VSSA, wherein said transistors of said first current steering and said second current steering switch are biased by voltages having a value lying between the value of said supply voltages VDDA and VSSA.