Circuit for performing voltage regulation
View Patent ↗A circuit ( 10, 100 ) is used to perform voltage regulation. In one embodiment, a voltage regulator ( 11 ) is used in conjunction with an output transistor ( 24 ) to form a circuit ( 10 ) which operates to regulate the voltage drop from a first node ( 30 ) to a second node ( 28 ). This second node ( 28 ) may be used to provide power to circuitry ( 27 ). The areas of several transistors ( 20–25 ) in circuit ( 10 ) may be adjusted so that negative and positive temperature coefficients may be balanced such that the circuit ( 10 ) behaves as desired over a range of voltages and temperatures. Note that in one embodiment, circuit ( 10 ) is a 2-terminal device.
1. A circuit having a first output terminal, comprising:
a first current source having an input coupled to a power supply terminal, and an output;
a second current source having an input coupled to the power supply terminal, and an output;
a first transistor having a first current electrode and a control electrode coupled to the output of the first current source, and a second current electrode coupled to the first output terminal;
a second transistor having a first current electrode coupled to the output of the second current source, a control electrode coupled to the control electrode of the first transistor, and a second current electrode;
an impedance having a first terminal coupled to the second current electrode of the second transistor and a second terminal coupled to the first output terminal; and
a third transistor having a first current electrode coupled to the power supply terminal, a control electrode coupled to the first current electrode of the second transistor, and a second current electrode coupled to the first output terminal,
wherein the first output terminal is not connected to a negative rail.
2. The circuit of claim 1 , wherein the first, second, and third transistors are MOS transistors.
3. The circuit of claim 2 , wherein the first, second, and third transistors are N channel transistors.
4. The circuit of claim 1 , wherein the first, second, and third transistors are bipolar transistors.
5. The circuit of claim 4 , wherein the bipolar transistors are NPN transistors.
6. The circuit of claim 1 , wherein the first and second current sources are MOS transistors.
7. The circuit of claim 1 , wherein a voltage provided at the first output terminal can be varied significantly when a voltage provided at the power supply terminal is not varied significantly.
8. The circuit of claim 1 , wherein the first and second current sources are further characterized as responding to a reduction in voltage on the first output terminal by supplying more current.
9. The circuit of claim 1 , wherein the impedance comprises an MOS transistor.
10. The circuit of claim 9 , wherein the MOS transistor has a first current electrode as the first terminal coupled to the second current electrode of the second transistor, a second current electrode as the second terminal coupled to the first output terminal, and a gate coupled to a ground terminal.
11. The circuit of claim 1 , further comprising a capacitive element having a first terminal coupled to the control electrode of the third transistor and a second terminal coupled to the first output terminal.
12. The circuit of claim 1 having a second output terminal further comprising:
a third current source having an input coupled to the first output terminal, and an output;
a fourth current source having an input coupled to the first output terminal, and an output;
a fourth transistor having a first current electrode and a control electrode coupled to the output of the third current source, and a second current electrode coupled to the second output terminal;
a fifth transistor having a first current electrode coupled to the output of the fourth current source, a control electrode coupled to the control electrode of the fourth transistor, and a second current electrode;
a second impedance having a first terminal coupled to the second current electrode of the fifth transistor and a second terminal coupled to the second output terminal; and
a sixth transistor having a first current electrode coupled the first output terminal, a control electrode coupled to the first current electrode of the fourth transistor, and a second cuirent electrode coupled to the second output terminal.
13. A circuit having a first output terminal, comprising:
a regulator circuit coupled between a positive power supply terminal and the first output terminal for providing a reference voltage; and
an output transistor having a first current electrode coupled to the positive power supply terminal, a control electrode for receiving the reference voltage, and a second current electrode coupled to the first output terminal;
wherein a voltage of the first output terminal exceeds a negative rail during operation of the circuit.
14. The circuit of claim 13 , wherein the regulator comprises:
a pair of current sources that each provide equal currents.
15. The circuit of claim 14 , wherein all of the current received by the regulator circuit passes to the first output terminal.
16. The circuit of claim 13 , wherein the regulator increases the reference voltage in response to a decrease in voltage at the first output terminal.
17. The circuit of claim 13 , wherein the regulator comprises:
a first current source having an input coupled to a power supply terminal, and an output;
a second current source having an input coupled to the power supply terminal, and an output;
a first transistor having a first current electrode and a control electrode coupled to the output of the first current source, and a second current electrode coupled to the first output terminal;
a second transistor having a first current electrode coupled to the output of the second current source for providing the reference voltage, a control electrode coupled to the control electrode of the first transistor, and a second current electrode; and
an impedance having a first terminal coupled to the second current electrode of the second transistor and a second terminal coupled to the first output terminal.
18. The circuit of claim 13 having a second output terminal, further comprising:
a second regulator circuit coupled between the first output terminal and the second output terminal for providing a second reference voltage; and
a second output transistor having a first current electrode coupled to the first output terminal, a control electrode for receiving the second reference voltage, and a second current electrode coupled to the second output terminal;
wherein all of the current received by the second regulator circuit passes to the second output terminal.
19. A circuit having a first output terminal, comprising:
a current mirror for establishing a reference current for establishing a reference voltage, wherein the reference current increases in response to a decrease in voltage at the output terminal;
an impedance that carries the reference current and that decreases in magnitude with increases in temperature; and
an output transistor for receiving the reference voltage and providing an output current at the output terminals,
wherein the voltage at the output terminal exceeds a negative rail voltage during operation of the circuit.
20. The circuit of claim 19 , wherein the current mirror comprises:
a first current source having an input coupled to a power supply terminal, and an output;
a second current source having an input coupled to the power supply terminal, and an output;
a first transistor having a first current electrode and a control electrode coupled to the output of the first current source, and a second current electrode coupled to the first output terminal; and
a second transistor having a first current electrode coupled to the output of the second current source for providing the reference voltage, a control electrode coupled to the control electrode of the first transistor, and a second current electrode coupled to the impedance.
21. The circuit of claim 19 having a second output terminal, further comprising:
a second current mirror for establishing a second reference current for establishing a second reference voltage, wherein the second reference current increases in response to a decrease in voltage at the second output terminal;
a second impedance that carries the second reference current and that decreases in magnitude with increases in temperature; and
a second output transistor for receiving the second reference voltage and providing a second output current at the second output terminal.