Voltage-mode line driving circuit having adaptive impedance matching

1. A voltage-mode line driving circuit, comprising:

a driving circuit, the driving circuit receiving, as an input signal, a feedback signal and outputting an output signal, the driving circuit comprising:

a front-end amplifier receiving the feedback signal as an amplifier input signal; and

a sampling circuit receiving the output signal from the front-end amplifier as an input, and outputting the feedback signal; and

an adaptive tuning circuit coupled to the driving circuit, the adaptive tuning circuit receiving as input signals the feedback signal and the output signal and adaptively outputting a modifying signal to the driving circuit which modifies the feedback signal by varying a gain of the sampling circuit based on a comparison of the feedback signal and the output signal.

2. The voltage-mode driving circuit of claim 1 , wherein:

the sampling circuit comprises an array of current mirrors coupled to the front-end amplifier; and the driving circuit further comprises:

a common mode feedback circuit coupled to an output of the sampling circuit and an input of the front-end amplifier, and providing the feedback signal to the front-end amplifier; and

at least one shunt circuit coupled between the input of the front-end amplifier and an output of the sampling circuit.

3. The voltage-mode driving circuit of claim 2 , wherein the adaptive tuning circuit comprises:

a comparator circuit, the comparator circuit receiving the feedback signal and the output signal as comparator input signals and outputting a comparison signal based on the comparison of the feedback signal and the output signal;

a counter circuit coupled to the comparator circuit and coupled to the sampling circuit, the counter circuit receiving a clock signal as a counter input signal, receiving the comparison signal output from the comparator circuit as a data input signal.

4. The voltage-mode driving circuit of claim 3 , wherein:

the counter outputs the modifying signal to the sampling circuit, the modifying signal changing depending on the comparison signal.

5. The voltage-mode driving circuit of claim 4 , wherein:

the gain of the sampling circuit is varied such that the sampling circuit increases a magnitude of the feedback signal when the feedback signal is less than the output signal and decreases the magnitude of the feedback signal when the feedback signal is greater than the output signal.

6. The voltage-mode driving circuit of claim 4 , wherein when the feedback signal is equal to the output signal, an input impedance of a load coupled to the voltage-mode driving circuit equals an output impedance of the amplifier.

7. The voltage-mode driving circuit of claim 3 , wherein the adaptive tuning circuit further comprises:

at least one flip-flop coupled between the counter circuit and the comparator circuit;

a first voltage divider coupled between the input current and the comparator; and

a second voltage divider coupled between the output voltage and the comparator.

8. The voltage-mode driving circuit of claim 3 , wherein the counter circuit comprises a digital 6-bit counter.

9. The voltage-mode driving circuit of claim 2 , wherein the output signal is a current driven through a load coupled to the amplifier, and the sampling circuit receives the output signal by sampling the current.

10. A voltage-mode line driving circuit having adaptive impedance matching, comprising:

a voltage driver configured to produce a first voltage to drive a first current through a load resistance;

a current sampling and feedback circuit comprising a current amplifier having a variable gain, the current sampling and feedback circuit configured to sample the first current and output a second current through a first resistance creating a second voltage; and

an adaptive tuning circuit configured to sample the first voltage and the second voltage to provide an amplification signal to the current sampling and feedback circuit, the amplification signal varying the gain of current amplifier being based on a comparison of the first voltage and the second voltage.

11. The voltage-mode line driving circuit of claim 10 , wherein:

the second current is an input of the voltage driver.

12. The voltage-mode line driving circuit of claim 10 , wherein the variable gain of the current amplifier remains constant when the first voltage equals the second voltage.

13. The voltage-mode line driving circuit of claim 10 , wherein:

the amplification signal increases the variable gain of the current amplifier when the first voltage is greater than the second voltage; and

the amplification signal decreases the variable gain of the current amplifier when the first voltage from the voltage amplifier circuit is less than the second voltage.

14. The voltage-mode line driving circuit of claim 11 , wherein:

the second current is increased when the first voltage is greater than the second voltage; and

the second current is decreased when a voltage from the voltage amplifier circuit is less than the voltage of the feedback signal.

15. The voltage-mode line driving circuit of claim 14 , wherein:

the first voltage decreases when the variable gain increases; and

the first voltage increases when the variable gain decreases.

16. The voltage-mode line driving circuit of claim 11 , further comprising:

a second resistance coupled between the output of the voltage amplifier circuit and the input of the voltage amplifier circuit; and

wherein the first resistance is coupled between the output of the current amplifier and the input of the voltage amplifier circuit.

17. The voltage-mode line driving circuit of claim 11 , wherein:

the line driving circuit has an output impedance;

the load has an input impedance; and

when the first voltage equals the second voltage, the output impedance is equal to the input impedance.