Driver Circuit and Method for Driving a Signal

Abstract

A driver circuit for driving a transmit signal for a line includes a signal amplifier configured to deliver a transmit signal, present at a signal input of the signal amplifier, amplified with a gain to a signal output, a line interface circuit connected between the signal output of the signal amplifier and the line, and a hybrid circuit connected to the line interface circuit, the hybrid circuit configured to suppress the transmit signal and couple a received signal received via the line to a signal input of the signal amplifier to provide impedance synthesis.

What is claimed is: 
     
         1 . A driver circuit for driving a transmit signal for a line, comprising:
 a signal amplifier configured to deliver a transmit signal, present at a signal input of the signal amplifier, amplified with a gain to a signal output;   a transformer having a secondary winding configured to be coupled to the line and a primary winding having a first terminal connected to the signal output of the signal amplifier and a second terminal connected to a terminating impedance; and   at least one hybrid circuit having a first feedback impedance configured to feed back the first connection of the primary winding to the signal input of the signal amplifier and a second feedback impedance configured to feed back the second connection of the primary winding to the signal input of the signal amplifier.   
     
     
         2 . A driver circuit according to  claim 1 , wherein a received signal received via the line is coupled out by the hybrid circuit. 
     
     
         3 . A driver circuit according to  claim 2 , wherein the received signal coupled out by the hybrid circuit is added to the transmit signal at a summation node for providing impedance synthesis. 
     
     
         4 . A driver circuit according to  claim 3 , wherein the synthesized impedance is adjustable independently of the gain of the signal amplifier. 
     
     
         5 . A driver circuit according to  claim 1 , further comprising a filter between the signal amplifier and the transformer and configured to filter high-frequency signal disturbances of the amplified transmit signal. 
     
     
         6 . A driver circuit according to  claim 5 , wherein a ratio of impedance values of the two feedback impedances contained in the hybrid circuit is such that the gain is independent of a filter transfer function of the filter. 
     
     
         7 . A driver circuit according to  claim 5 , wherein the filter is an out-of-band filter. 
     
     
         8 . A driver circuit according to  claim 1 , wherein the signal amplifier is a class-D signal amplifier configured to deliver a pulse-width-modulated transmit signal. 
     
     
         9 . A driver circuit according to  claim 7 , wherein the filter is an analogue low-pass filter configured to filter a high-frequency switching noise of the pulse-width-modulated amplified transmit signal. 
     
     
         10 . A driver circuit according to  claim 1 , wherein the feedback impedances are formed by resistors. 
     
     
         11 . A driver circuit according to  claim 1 , wherein the driver circuit is of differential construction. 
     
     
         12 . A driver circuit according to  claim 1 , wherein the line is a telephone line. 
     
     
         13 . A driver circuit for driving a transmit signal for a telephone line, comprising:
 a signal amplifier configured to amplify a transmit signal, present at a signal input of the signal amplifier, with a gain and deliver the transmit signal to a signal output;   a filter configured to filter high-frequency signal disturbances of the amplified transmit signal in accordance with a filter transfer function;   a transformer having a secondary winding configured to be coupled to the telephone line and a primary winding having a first terminal connected to the filter and a second terminal connected to a terminating impedance;   a first feedback loop configured to feed back the first connection of the primary winding to the signal input of the signal amplifier via a first feedback resistor;   a second feedback loop configured to feed back the second connection of the primary winding to the signal input of the signal amplifier via a second feedback impedance; and   wherein a ratio of the resistance values of the two feedback impedances is such that the gain is independent of the filter transfer function of the filter.   
     
     
         14 . A driver circuit according to  claim 13 , wherein the signal amplifier is a class-D signal amplifier configured to deliver a pulse-width-modulated transmit signal. 
     
     
         15 . A driver circuit according to  claim 14 , wherein the filter is an analogue low-pass filter configured to filter a high-frequency switching noise of the pulse-width-modulated amplified transmit signal. 
     
     
         16 . A driver circuit according to  claim 13 , wherein the feedback impedances are formed by resistors. 
     
     
         17 . A driver circuit according to  claim 13 , wherein the second feedback loop is configured to generate a synthesized line terminating impedance. 
     
     
         18 . A driver circuit according to  claim 13 , wherein the driver circuit is of differential construction. 
     
     
         19 . A driver circuit for driving a transmit signal for a line, comprising:
 a signal amplifier configured to deliver a transmit signal, present at a signal input of the signal amplifier, amplified with a gain to a signal output;   a line interface circuit connected between the signal output of the signal amplifier and the line; and   a hybrid circuit connected to the line interface circuit, the hybrid circuit configured to suppress the transmit signal and couple a received signal received via the line to a signal input of the signal amplifier to provide impedance synthesis.   
     
     
         20 . A driver circuit according to  claim 19 , wherein the driver circuit is of differential construction.