Electronic inductor with transmit signal telephone line driver

A signal driving stage for use in a telephone line interface circuit, the signal driving stage comprising:

• an amplifier;
• a voltage divider coupled with the amplifier, the voltage divider configured to provide a DC reference to the amplifier;
• and
• an inductor transistor coupled with the amplifier such that the amplifier and the inductor transistor form a voltage-controlled current source,
• the signal driving stage configured to:
• drive a linearly varying signal directly onto a telephone line;
• set a DC loop current;
• block distortion generated in the signal driving stage from effecting the linearly varying signal;
• and
• provide an on-hook resistance that is large enough to allow the telephone line interface circuit to be connected to the telephone line even when on-hook.

A signal driving stage for use in a telephone line interface circuit, the signal driving stage comprising:

• an amplifier;
• a voltage divider coupled with the amplifier, the voltage divider configured to provide a DC reference to the amplifier;
• an inductor transistor coupled with the amplifier such that the amplifier and the inductor transistor form a voltage-controlled current source;
• and
• an emitter resistor coupled between the inductor transistor and a ground,
• the signal driving stage configured to:
• drive a linearly varying signal onto a telephone line;
• set a DC loop current;
• block distortion generated in the signal driving stage from effecting the linearly varying signal;
• and
• cause a current in the telephone line to vary linearly in response to a transmit voltage signal, and wherein the current is inversely proportional to a resistance of the emitter resistor.

A signal driving stage for use in a telephone line interface circuit, the signal driving stage comprising:

• an amplifier;
• a voltage divider coupled with the amplifier, the voltage divider configured to provide a DC reference to the amplifier;
• an inductor transistor coupled with the amplifier such that the amplifier and the inductor transistor form a voltage-controlled current source;
• a Darlington transistor coupled with the inductor transistor;
• and
• a plurality of selectable feedback paths configured to provide feedback from the combination of the inductor transistor and the Darlington transistor at different feedback points to the amplifier,
• the signal driving stage configured to:
• drive a linearly varying signal onto a telephone line;
• set a DC loop current;
• block distortion generated in the signal driving stage from effecting the linearly varying signal;
• and
• provide intelligent control of the DC operating point and the linearly varying signal through selection of the appropriate feedback path.

A modem comprising a telephone line interface circuit, the modem configured to communicate signals over a telephone line, the telephone line interface circuit comprising:

• an impedance matching circuit configured to match an impedance of the telephone line interface circuit to an impedance of the telephone line;
• and
• a signal driving stage comprising an amplifier, the signal driving stage configured to:
• drive the communication signals directly onto the telephone line;
• set a DC operating voltage without effecting an AC response of the signal driving stage relative to a transmit voltage signal, and
• provide an on-hook resistance that is large enough to allow the line interface circuit to be connected to the telephone line even when on-hook.

A modem comprising a telephone line interface circuit, the modem configured to communicate signals over a telephone line, the telephone line interface circuit comprising:

• an impedance matching circuit configured to match an impedance of the telephone line interface circuit to an impedance of the telephone line;
• and
• a signal driving stage comprising an amplifier, the signal driving stage configured to:
• set a DC operating voltage without effecting an AC response of the signal driving stage relative to a transmit voltage signal,
• provide an on-hook resistance that is large enough to allow the line interface circuit to be connected to the telephone line even when on-hook, and
• provide intelligent control of the DC operating voltage.