Low dropout regulator using gate modulated diode

• US 6,956,429 B1
• Filed: 02/09/2004
• Issued: 10/18/2005
• Est. Priority Date: 02/09/2004
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Elbanhawy, Alaa
• Primary Examiner(s): Zweizig, Jeffrey
• Application Number:
  US10/774,581
• Time in Patent Office: 617 Days
• Field of Search: 327/530, 327/534, 327/535, 327/537, 327/538, 327/540, 327/541, 327/543
• US Class Current: 327/541
• CPC Class Codes: G05F 1/575 characterised by the feedback circuit

Abstract

A voltage regulator includes an input terminal at which an input voltage is applied and an output terminal at which an output voltage is provided to a load. The load defines a load current. A gate modulated diode is connected between the input terminal and the output terminal. The gate modulated diode has a forward voltage drop that is controllable by a voltage signal applied to a gate of the gate modulated diode. A first operational amplifier, capable of operating with a low supply voltage, is operable to apply the voltage signal at the gate of the gate modulated diode to control the forward voltage drop. The output voltage is regulated to a predetermined low voltage when the load current is within an operational range for the voltage regulator.

Claims

1. A voltage regulator comprising:

an input terminal at which an input voltage is applied;

an output terminal at which an output voltage is provided to a load, wherein the load defines a load current;

a gate modulated diode connected between the input terminal and the output terminal, the gate modulated diode having a forward voltage drop that is controllable by a voltage signal applied to a gate of the gate modulated diode, wherein the gate modulated diode comprises a transistor operating at below gate threshold voltage;

a first operational amplifier capable of operating with a low supply voltage, the first operational amplifier operable to apply the voltage signal at the gate of the gate modulated diode to control the forward voltage drop;

wherein the output voltage is regulated to a predetermined low voltage when the load current is within an operational range for the voltage regulator.

2. The voltage regulator of claim 1 wherein the supply voltage has a value of not more than 1.2V.

3. The voltage regulator of claim 1 wherein the gate modulated diode comprises a MOSFET.

4. The voltage regulator of claim 1 wherein the supply voltage is the same as the input voltage.

5. The voltage regulator of claim 1 wherein the output voltage has a value of not more than 1.0V.

6. The voltage regulator of claim 1 comprising a second operational amplifier operable to provide a reference voltage to the first operational amplifier.

7. The voltage regulator of claim 1 comprising a resistor coupled between the input terminal and an output node of the first operational amplifier, the resistor operable to pull-up the output node of the first operational amplifier.

8. The voltage regulator of claim 1 comprising a capacitor connected to the output terminal, the capacitor operable to stabilize the output voltage.

9. A voltage regulator comprising:

an input terminal to which a low source voltage can be applied;

an output terminal at which a low output voltage is provided;

a transistor operating at below gate threshold voltage and connected between the input terminal and the output terminal, the transistor having a forward voltage drop which can be changed in response to a voltage applied to a gate of the transistor; and

means connected to the gate of the transistor for controlling the forward voltage drop of the transistor so that the low voltage output is maintained at a substantially constant value, the means for controlling capable of operating with the low source voltage.

10. The voltage regulator of claim 9 wherein the low source voltage has a value of not more than 1.2V.

11. The voltage regulator of claim 9 wherein the transistor implements a gate modulated diode.

12. The voltage regulator of claim 9 wherein the transistor comprises a MOSFET.

13. The voltage regulator of claim 9 wherein the output voltage has a value of not more than 1.0V.

14. The voltage regulator of claim 9 wherein the means for controlling comprises an operational amplifier.

15. The voltage regulator of claim 9 comprising a capacitor connected to the output terminal, the capacitor operable to stabilize the output voltage.