Systems and methods to provide reference voltage or current

1. A current mirroring circuit comprising:

a first portion having a first resistor and a first transistor, the first transistor having a control terminal coupled to a control terminal of a first diode-connected transistor; and

a second portion having a second resistor and a second transistor, the second transistor having a control terminal coupled to a control terminal of a second diode-connected transistor, the first portion being in electrical communication with a first power level and the second portion being in electrical communication with a second power level, the first portion being coupled to the second portion, wherein the first diode-connected transistor is included in a first diode-connected pair of transistors including an NMOS transistor and a PMOS transistor, further wherein the second diode-connected transistor is included in a second diode-connected pair of transistors including an NMOS transistor and a PMOS transistor.

2. The current mirroring circuit of claim 1 , further including a reference voltage terminal disposed between the first portion and the second diode-connected pair of transistors.

3. The current mirroring circuit of claim 1 , wherein a ratio of a drive strength of the first transistor to a drive strength of the first diode-connected transistor is 1/X, further wherein a ratio of a drive strength of the second transistor to a drive strength of the second diode-connected transistor is 1/X.

4. The current mirroring circuit of claim 1 , wherein the first power level corresponds to VDD, and wherein the second power level corresponds to ground or VSS.

5. The current mirroring circuit of claim 1 , wherein the current mirroring circuit is disposed on a same semiconductor chip with a digitally controlled oscillator and a power supply of the digitally controlled oscillator, wherein the power supply is configured to generate a power supply voltage corresponding to a reference voltage from the current mirroring circuit, and further wherein the digitally controlled oscillator is configured to receive the power supply voltage.

6. The current mirroring circuit of claim 1 , wherein the first resistor and the first transistor are coupled in series with the second diode-connected transistor, further wherein the second resistor and the second transistor are coupled in series with the first diode-connected transistor.

7. The current mirroring circuit of claim 1 , wherein the first portion and the second portion are arranged having point reflection symmetry.

8. The current mirroring circuit of claim 1 , further comprising a startup circuit having a third transistor, the third transistor having a first terminal coupled with the first power level, a second terminal coupled with the first transistor and the second diode-connected transistor, and a control terminal coupled with a voltage divider.

9. A method comprising:

mirroring a first current and a second current, wherein a path of the first current between a power source and ground includes a first resistor, a first transistor, and a first diode-connected NMOS and PMOS pair, further wherein a path of the second current between the power source and ground includes a second resistor, a second transistor, and a second diode-connected NMOS and PMOS pair, wherein mirroring includes:

maintaining a gate of the first transistor and gates of the second diode-connected NMOS and PMOS pair at a same voltage;

maintaining a gate of the second transistor and the first diode-connected NMOS and PMOS pair at a same voltage; and

outputting a reference voltage from a node disposed between the first transistor and the first diode-connected NMOS and PMOS pair.

10. The method of claim 9 , wherein the reference voltage is equal to a sum of gate-source voltages of the first diode-connected NMOS and PMOS pair.

11. The method of claim 9 , further comprising:

receiving the reference voltage at a power supply; and

generating a power supply voltage corresponding to a level of the reference voltage.

12. The method of claim 11 , further comprising:

receiving the power supply voltage at a digitally controlled oscillator, wherein the reference voltage comprises a compensation voltage level corresponding to a process or temperature variation affecting devices within the digitally controlled oscillator; and

outputting a clock signal from the digitally controlled oscillator.

13. The method of claim 9 , further comprising biasing a node disposed between the first transistor and the first diode-connected NMOS and PMOS pair at a voltage corresponding to an operating point of a current mirroring circuit.

14. A semiconductor device comprising:

a first current path between a power source and ground, wherein the first current path includes in series: a first resistor, a first transistor, and a first diode-connected NMOS and PMOS pair;

a second current path between the power source and ground, wherein the second current path includes in series: a second resistor, a second transistor, and a second diode-connected NMOS and PMOS pair, wherein a control terminal of the first transistor and a control terminal of the second diode-connected NMOS and PMOS pair are coupled and wherein a control terminal of the second transistor is coupled to a control terminal of the first diode-connected NMOS and PMOS pair; and

a reference voltage output terminal in communication with the first current path and disposed between the first transistor and the first diode-connected NMOS and PMOS pair.

15. The semiconductor device of claim 14 , further comprising:

a voltage regulator configured to receive a reference voltage from the reference voltage output terminal and configured to provide an output voltage corresponding to a level of the reference voltage; and

a digitally controlled oscillator configured to receive the output voltage as a power supply.

16. The semiconductor device of claim 14 , wherein a ratio of a drive strength of the first transistor to a drive strength of a PMOS transistor of the first diode-connected NMOS and PMOS pair is 1/X, further wherein a ratio of a drive strength of the second transistor to a drive strength of an NMOS transistor of the second diode-connected NMOS and PMOS pair is 1/X.

17. The semiconductor device of claim 16 , wherein the first transistor includes a PMOS transistor, and wherein the second transistor includes an NMOS transistor.

18. The semiconductor device of claim 14 , wherein the first transistor and the second transistor comprise bipolar transistors.

19. The semiconductor device of claim 14 , further comprising a startup circuit having a third transistor, the third transistor having a first terminal coupled with the power source, a second terminal coupled to the first transistor and the first diode-connected NMOS and PMOS pair, and a control terminal coupled with a voltage divider.

20. The semiconductor device of claim 14 , wherein the first current path and the second current path have point reflection symmetry.

21. The semiconductor device of claim 14 , wherein the reference voltage output terminal is configured to provide a reference voltage equal to a voltage drop across the first diode-connected NMOS and PMOS pair.

22. A semiconductor device comprising:

a first portion having first means for providing a nonlinear voltage drop, the first means for providing a nonlinear voltage drop including a first resistor and having a control terminal coupled to a gate terminal of second means for providing a nonlinear voltage drop, the second means for providing a nonlinear voltage drop including a first non-linear device; and

a second portion having third means for providing a nonlinear voltage drop, the third means for providing a nonlinear voltage drop including a second resistor and having a control terminal coupled to a gate terminal of fourth means for providing a nonlinear voltage drop, the fourth means for providing a nonlinear voltage drop including a second non-linear device, the first portion being in electrical communication with a power supply and the second portion being in electrical communication with ground, the first portion being coupled to the second portion, wherein the first means for providing a nonlinear voltage drop includes a first transistor in series with the first resistor, wherein the first resistor is disposed between the first transistor and the power supply, and wherein the first non-linear device includes a first diode-connected NMOS and PMOS pair.

23. The semiconductor device of claim 22 , wherein the third means for providing a nonlinear voltage drop includes a second transistor in series with the second resistor, wherein the second resistor is disposed between the second transistor and ground;

wherein the second non-linear device includes a second diode-connected NMOS and PMOS pair disposed between the first means for providing a nonlinear voltage drop and ground.

24. The semiconductor device of claim 23 , wherein a ratio of a drive strength of the first transistor to a drive strength of a PMOS transistor of the first diode-connected NMOS and PMOS pair is 1/X, further wherein a ratio of a drive strength of the second transistor to a drive strength of an NMOS transistor of the second diode-connected NMOS and PMOS pair is 1/X.

25. The semiconductor device of claim 22 , further including a reference voltage terminal disposed between the first portion and the fourth means for providing a nonlinear voltage drop.

26. The semiconductor device of claim 25 , wherein the first portion and the second portion are disposed on a same chip with means for producing a clock signal and means for providing an input voltage to the clock signal producing means, wherein the input voltage providing means includes means for generating a power supply voltage corresponding to a reference voltage from the reference voltage terminal.

27. The semiconductor device of claim 22 , wherein the first portion and the second portion are arranged having point reflection symmetry.

28. The semiconductor device of claim 22 , further comprising startup means for bringing the first portion to an operating point of a current mirroring circuit.