On-chip series terminated cmos(bi-cmos) driver

Abstract

A terminated driver circuit 10 having a controlled output impedance includes an external impedance 12 connected to a bias generator circuit 20 which is operable to generate a plurality of bias voltages in response to a reference current generated by bias generator circuit 20 wherein the reference current magnitude is a function of external impedance 12. An output driver circuit 30 is connected to bias generator circuit 20. Output driver circuit 30 has a plurality of output devices connected to a transmission line and is operable to receive the plurality of bias voltages from bias generator circuit 20 and multiplex them such that only a single bias voltage is driving a single output device at a time. The plurality of bias voltages causes the plurality of output devices to have specific, controlled impedances when conducting wherein the controlled output impedances match the characteristic impedance of a transmission line 40 being driven by terminated driver circuit 10 thereby reducing waveform reflections.