Multi-mode amplifier

1. An amplifier capable of operating in multiple modes, the amplifier comprising:

first and second voltage inputs; and

first and second bi-directional current outputs, wherein the first bi-directional current output and the second bi-directional current output have substantially the same amplitude and substantially the same polarity,

wherein the amplifier operates in a first mode when the first bi-directional current output and the second bi-directional current output are coupled together, and

wherein the amplifier operates in a second mode when one of the first bi-directional current output and the second bi-directional current output is coupled to the second voltage input.

2. The amplifier of claim 1 , wherein the amplifier functions as an operational amplifier while in the first mode.

3. The amplifier of claim 1 , wherein the amplifier functions as a type-2 current conveyor while in the second mode.

4. The amplifier of claim 1 , wherein the amplifier also operates in the first mode when one of the first bi-directional current output and the second bi-directional current output is floating.

5. The amplifier claim 1 , wherein the first voltage input and the second voltage input each have a high impedance.

6. The amplifier of claim 1 , wherein the first bi-directional current output and the second bi-directional current output each have a high impedance.

7. The amplifier of claim 1 , wherein the first voltage input comprises a noninverting voltage input and the second voltage input comprises an inverting voltage input.

8. The amplifier of claim 1 , wherein the first bi-directional current output and the second bi-directional current output each comprise an amplified version of a difference between the first voltage input and the second voltage input.

9. The amplifier of claim 1 , wherein the amplifier comprises a differential amplifier comprising an input stage that accepts the first and second voltage inputs, a first output stage that provides the first bi-directional current output, and a second output stage that provides the second bi-directional current output.

10. The amplifier of claim 1 , wherein amplifier further comprises:

a first output stage comprising a first transistor and a second transistor, the first transistor having a source coupled to a first voltage supply and a drain coupled to a drain of the second transistor, the second transistor having a source coupled to a second voltage supply, the drain of the first transistor and the drain of the second transistor acting as the first bi-directional current output; and

a second output stage comprising a third transistor and a fourth transistor, the third transistor having a source coupled to the first voltage supply and a drain coupled to a drain of the fourth transistor, the fourth transistor having a source coupled to the second voltage supply, the drain of the third transistor and the drain of the fourth transistor acting as the second bi-directional current output.

11. The amplifier of claim 10 , wherein the amplifier further comprises

a differential input stage comprising a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, and a current source,

wherein the fifth transistor has a source coupled to the first voltage supply via the current source, a drain coupled to a drain of the seventh transistor, and a gate that acts as the first voltage input of the amplifier,

wherein the sixth transistor has a source coupled to the first voltage supply via the current source, a drain coupled to a drain of the eighth transistor, and a gate that acts as the second voltage input of the amplifier,

wherein the seventh transistor has a source coupled to the second voltage supply, and a gate coupled to the drain of the seventh transistor, the drain of the seventh transistor acting as a first output of the differential input stage,

wherein the eighth transistor has a source coupled to the second voltage supply, and a gate coupled to the drain of the eighth transistor, the drain of the eighth transistor acting as a second output of the differential input stage,

wherein the first differential output stage further comprises a ninth transistor and a tenth transistor,

wherein the ninth transistor has a source coupled to the second voltage supply, a drain coupled to a drain of the tenth transistor, and a gate coupled to the first output of the differential input stage,

wherein the tenth transistor has a source coupled to the first voltage supply, and a gate coupled to the drain of the tenth transistor,

wherein a gate of the second transistor and a gate of the fourth transistor are both coupled to the second output of the differential input stage, and

wherein a gate of the first transistor and a gate of the third transistor are both coupled to the gate of the tenth transistor.

12. The amplifier of claim 1 ,

wherein the first voltage input is coupled to ground via a first diode and a first resistor,

wherein the first diode is coupled in parallel with the first resistor,

wherein the first voltage input is coupled to the first bi-directional current output via a second resistor;

wherein the second voltage input is coupled to ground via a third resistor, a fourth resistor, and a second diode,

wherein the fourth resistor is coupled in series with the second diode,

wherein the third resistor is coupled in parallel with the fourth resistor and the second diode;

wherein the second voltage input is coupled to the first bi-directional current output via a fifth resistor,

wherein the second bi-directional current output is coupled to ground via a sixth resistor, and

wherein a voltage across the sixth resistor comprises a voltage reference.

13. The amplifier of claim 12 , wherein the first bi-directional current output and the second bi-directional current output provide a constant bandgap current.

14. An amplifier capable of operating in multiple modes, the amplifier comprising:

first and second voltage inputs;

first and second bi-directional current outputs, wherein the first bi-directional current output and the second bi-directional current output have substantially the same amplitude and substantially the same polarity; and

a third bi-directional current output, wherein the third bi-directional current output has an amplitude that is substantially the same as the amplitudes of the first and second bi-directional current outputs, and wherein the third bi-directional current output has a polarity that is substantially opposite to the polarities of the first and second bi-directional current outputs.

15. The amplifier of claim 14 , wherein the amplifier functions as a four-terminal floating nullor when one of the first bi-directional current output and the second bi-directional current output is floating.

16. An amplifier capable of operating in multiple modes, the amplifier comprising:

first and second voltage inputs; and

first and second bi-directional current outputs, wherein the first bi-directional current output and the second bi-directional current output have substantially the same amplitude and substantially the same polarity,

wherein the differential amplifier operates in a first mode when the first bi-directional current output and the second bi-directional current output are coupled together, and

wherein the differential amplifier operates in a second mode when one of the first bi-directional current output and the second bi-directional current output is coupled to the second voltage input.

17. The amplifier of claim 16 , wherein the differential amplifier functions as an operational amplifier while in the first mode.

18. The amplifier of claim 16 , wherein the differential amplifier functions as a type-2 current conveyor while in the second mode.

19. The amplifier of claim 16 , wherein the first bi-directional current output and the second bi-directional current output each comprise an amplified version of a difference between the first voltage input and the second voltage input.