Output buffer for driving a symmetrical transmission line

An output buffer circuit for differentially driving a symmetrical transmission line (TL), comprising

• output transistors (N3 to N6) each having a controllably conductive path, the conductive paths of said output transistors being connected to constitute a bridge driver circuit;
• said bridge driver circuit having a signal input (Din) for receiving a data signal to be transmitted over said transmission line (TL), a signal output (X, Y) for connection with said transmission line (TL), and a power supply input;
• a power supply circuit for supplying an upper power supply potential (Vu) and a lower power supply potential (V) to said bridge driver circuit;
• said power supply circuit being adapted to constitute a voltage source having a lower voltage source potential and an upper voltage source and a source impedance (Rs);
• a sum of said source impedance (Rs) and of an ON impedance (Ru, R) of a diagonal of said bridge driver circuit being selected to match the characteristic impedance of said transmission line;
• said power supply circuit comprising a voltage generator circuit for biasing the lower voltage source potential at a predetermined level;
• characterized in that
• said power supply circuit comprises a series connection of transistors (N14, N15) connected to constitute a push pull stage;
• the output of said push pull stage being connected with said power supply input of said bridge driver circuit.