OUTPUT BUFFER FOR DRIVING A SYMMETRICAL TRANSMISSION LINE

摘要

An output buffer circuit for differentially driving a symmetrical transmission line comprises a bridge driver circuit (1) having a power supply input (11, 12) and outputs (X, Y) for connection with a transmission line (TL). A power supply circuit (2) provides an upper power supply potential (Vu) and a lower power supply potential (V1) to the bridge driver circuit. The power supply circuit (2) constitutes a voltage source with a source impedance (Rs). The sum of the source impedance (Rs) and the ON-impedance (Ru, R1) of a bridge diagonal of the bridge driver circuit is matched to the characteristic impedance of the transmission line. A voltage generator circuit (22) biases the lower voltage source potential to have a predetermined level. The output buffer circuit according to the invention allows matching the transmission line at the transmitter side both with regard to the differential characteristic impedance and with regard to the common mode characteristic impedance.