Amplifier and line driver for broadband communications

A line matching network for a line driver coupling a data transceiver to a transmission line via a transformer, said line driver including an amplifier circuit for amplifying an input signal voltage from said data transceiver, said amplifier circuit having a first output stage, a second output stage, and a feedback path from said first output stage to an input of said amplifier circuit, said line matching network comprising:

• a first terminal adapted to being coupled to said first output stage;
• a second terminal adapted to being coupled to said second output stage;
• and
• a plurality of matching circuits coupled in parallel between said first terminal and second terminal, each of said matching circuits having a different filter characteristic corresponding to a different type of the transmission line.

An amplifier circuit for amplifying an input signal voltage, used for a line driver coupling a signal from a data transceiver to a transmission line having a load impedance via a transformer with a turns ratio of 1:n, said amplifier circuit comprising:

• an output node for outputting an output signal voltage from said amplifier circuit;
• a first output stage;
• a second output stage coupled to said output node;
• and
• a line matching network coupled between said first output stage and said second output stage, for compensating variations in said load impedance, so that a synthesized output impedance of said line driver substantially matches an actual load impedance Z of the transmission line.

A line driver for coupling a data transceiver to a transmission line having a load impedance via a transformer with a turns ratio of 1:n, said line driver comprising:

• an input port for receiving an input signal voltage from said data transceiver, said input port including a first input terminal and a second input terminal;
• an output port for supplying an output signal voltage to said transformer, said output port including a first output terminal and a second output terminal;
• a first-stage amplifier coupled to said input port, said first-stage amplifier having a first input coupled with said first input terminal, a second input coupled with said second input terminal, a first output, and a second output;
• a first second-stage amplifier coupled to said first output, said first second-stage amplifier including a first output stage coupled to a first node, and a second output stage coupled to a second node, said second node being coupled to said first output terminal;
• a second second-stage amplifier coupled to said second output, said second second-stage amplifier including a first output stage coupled to a third node, and a second output stage coupled to a fourth node, said fourth node being coupled to said second output terminal;
• a first feedback path from said first node to said first input;
• a second feedback path from said third node to said second input;
• an output resistor coupled between said first node and said third node;
• and
• a first line matching network coupled between said first node and said second node, and a second line matching network coupled between said third node and said fourth node, for compensating variations in said load impedance, so that a synthesized output impedance of said line driver substantially matches an actual load impedance Z of the transmission line.

A line driver for coupling a data transceiver to a transmission line having a load impedance via a transformer with a turns ratio of 1:n, said line driver comprising:

• an input port for receiving an input signal voltage from said data transceiver, said input port including a first input terminal and a second input terminal;
• an output port for supplying an output signal voltage to said transformer, said output port including a first output terminal and a second output terminal;
• a first-stage amplifier coupled to said input port, said first-stage amplifier having a first input coupled with said first input terminal, a second input coupled with said second input terminal, a first output, and a second output;
• a first second-stage amplifier coupled to said first output, said first second-stage amplifier including a first output stage coupled to a first node, and a second output stage coupled to a second node, said second node being coupled to said first output terminal;
• a second second-stage amplifier coupled to said second output, said second second-stage amplifier including a first output stage coupled to a third node, and a second output stage coupled to a fourth node, said fourth node being coupled to said second output terminal;
• a first feedback path from said first node to said first input;
• a second feedback path from said third node to said second input;
• a first output resistor coupled between said first node and said second node;
• a second output resistor coupled between said third node and said fourth node;
• and
• a line matching network coupled between said first node and said third node, for compensating variations in said load impedance, so that a synthesized output impedance of said line driver substantially matches an actual load impedance Z of the transmission line.