US 6,275,078 B1 · Self-adjustable impendance line driver

Abstract

A pair of equivalent controlled impedance buffers are connected in a push-pull configuration to a transformer primary coil. A pair of equivalent pre-drivers are connected to the pair of buffers. Each pre-driver receives a driver input signal and outputs a buffer input signal and a proportional flyback compensation signal. Each buffer receives the buffer input signal generated from one of the pre-drivers for buffered output as a line driver signal to the primary coil which induces a flyback voltage effect in each buffer. Each buffer further receives the flyback compensation signal generated from the other one of the pre-drivers, with the buffer operating to cancel the flyback voltage effect induced in that buffer using the flyback compensation signal received from the other one of the pre-drivers. An adjustment circuit further outputs an adjustment signal for application to an adjustable current source. By manipulating the adjustable current source with the adjustment signal, the output impedance of the buffer can be made to match the characteristic impedance of a transmission line connected to the transformer secondary coil.

Claims33

Dependent claims

A line driver circuit, comprising:

a buffer including an adjustable current source and having a signal input and a signal output that provides a line driver output signal buffered from the signal input, the buffer further including a tuning input connected to the adjustable current source;
and
a tuning circuit, comprising:
a first current source producing a first current;
a second current source producing a second current;
a current mirror having a fixed branch connected to receive the first current and an adjustable branch connected to receive the second current, the current mirror further having a control input connected to the adjustable branch and having an output;
and
a comparison circuit receiving the current mirror output for comparison to predetermined output voltage limits, the comparison circuit generating a control signal for application to the control input to maintain a voltage of the current mirror output within the predetermined output voltage limits and generating a tuning signal for application to the tuning input of the buffer to adjust operation of the adjustable current source to control an output impedance of the buffer.

5 more elements

A line driver circuit for connection to a transformer having a primary coil, comprising:

a pair of equivalent buffers for connection to a first and second terminals of the primary coil, each buffer receiving a buffer input signal for buffered output as a line driver signal to the primary coil, each buffer further including an impedance circuit that sets an output impedance of the buffer, the impedance circuit having a tuning input connected to an adjustable current source whose operation controls impedance circuit setting of the buffer output impedance;
and
a tuning circuit that generates a tuning signal that is connected to the tuning input of each buffer to adjust operation of the adjustable current source to set the buffer output impedance to substantially match a characteristic impedance of a transmission line connected to the transformer.

A line driver circuit for connection to a transformer having a primary coil, comprising:

a pair of equivalent controlled impedance buffers for connection a first and second terminals of the primary coil, each buffer receiving a buffer input signal for buffered output as a line driver signal to the primary coil, each buffer further including a tuning input connected to an adjustable current source whose operation effectuates control over buffer output impedance;
and
a tuning circuit that generates a tuning signal that is connected to the tuning input of each buffer to adjust operation of the adjustable current source to control the buffer output impedance, wherein the tuning circuit comprises:
a first current source producing a first current;
a second current source producing a second current;
a current mirror having a fixed branch connected to receive the first current and an adjustable branch connected to receive the second current, the current mirror further having a control input to the adjustable branch and having an output;
and
a comparison circuit receiving the current mirror output for comparison to predetermined output voltage limits, the comparison circuit generating a control signal for application to the control input of the adjustable branch to maintain the control mirror output within the predetermined output voltage limits and generating the tuning signal for application to the tuning input of the buffer to adjust operation of the adjustable current source to control the output impedance of the buffer.

5 more elements

Dependencies are inferred from the claim text.

Self-adjustable impendance line driver

Life of this patent

Self-adjustable impendance line driver

Life of this patent

Abstract

Claims33