Patent ID: 6566947
Filing Date: 2003-05-20
Classification: H03H

Abstract:
A line driver, comprising:an amplifier having an inverting input, a non-inverting input and an output; a transformer having a primary winding and a secondary winding with a predetermined ratio of the primary winding to the secondary winding of 1:n, the primary winding having a first terminal connected to the output of the amplifier and having a second terminal, the secondary winding being connectable to a transmission line having a characteristic impedance; a reference impedance having a first terminal connected to the second terminal of the primary winding at a junction node and having a second terminal connected to a ground reference; an input impedance having a first terminal connected to the inverting input of the amplifier and a second terminal connectable to a voltage source; a first feedback impedance having a first terminal connected to the junction node and a second terminal connected to the inverting input of the amplifier; a second feedback impedance having a first terminal connected to the output of the amplifier and having a second terminal connected to the inverting input of the amplifier; wherein the reference impedance has a value equal to n2Kâ€ƒtimes the characteristic impedance of the transmission line and wherein the second feedback impedance has a value equal to (Kâˆ’1) times the value of the first feedback impedance, where K is a real number; and wherein the first feedback impedance is chosen to be much greater than the reference impedance so that the voltage at the output of the amplifier is substantially equal to (K+1) times the voltage at the junction node; whereby the line driver has an output impedance substantially equal to K times the reference impedance and the line driver has a gain substantially equal to half of the negative of the ratio of the value of the second feedback impedance to the value of the input impedance.