Analog Devices,inc.

Ojas M Choksi

Faramarz Sabouri

Alfred R Mangino

Bindu Gupta

A transceiver system is disclosed for use in a telecommunication system. The transceiver system includes a transmission circuit with a differential transmitter input coupled via a transmitter input stage to a differential input of a transmission amplifier in an embodiment. The transmitter input stage includes a trimmable resistor, one end of which is coupled to a positive transmit input signal, and the other end of which is coupled to a negative transmit input signal. The transceiver system also includes a receiver circuit with a differential receiver output coupled to a differential input of a receiver amplifier, and further includes a transmission line interface circuit coupled to a differential output of said transmission amplifier and to a differential input of said receiver amplifier. In accordance with other embodiments, the receiver amplifier includes an input stage that includes a first plurality of capacitors and a feedback circuit that includes a second plurality of capacitors.

Line interface system

A line interface performs echo cancellation without the use of a hybrid filter network and includes a transmit path having a line driver, a single matching network terminating the line, and a single transformer. The transformer uses split windings on both the primary side and the secondary (line) side. Each half of the primary side is tapped to obtain a turns ratio of N:N, while each half of the secondary side of the transformer has N windings. The single matching impedance is coupled in parallel between the first winding and the second winding on each half of the primary side. Either the voltage across the matching impedance or the voltage across the receive terminals is bootstrapped to the receive signal through multiple negative feedbacks. The transfer function of the line driver is shaped as a first-order high-pass filter (HPF) to reject any out-of-band noise and distortion components.

Line interface with analog echo cancellation

A JFET switch select circuit including a first current mirror system including a first high current mirror circuit referenced to high rail voltage and a first low current mirror circuit referenced to a low rail voltage, a second current mirror system including a second high current mirror circuit referenced to the high rail voltage and a second low current mirror circuit referenced to the low rail voltage, and a comparator circuit responsive to an input voltage and a reference voltage for directing current from a current supply circuit to one of the first and second high current mirror circuits and one of the first and second low current mirror circuits for saturating a switching device of one of the first and second high current mirror circuits to set a first output voltage proximate to a high rail voltage and for saturating a switching device of one of the first and second low current mirror circuits to set a second output voltage proximate a low rail voltage.

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Monmouth Junction, NJ, United States of America

Ojas M Choksi