Circuits for generating a reference voltage

1. A circuit of generation of a reference voltage by a first MOS transistor of a first channel type connected to a first terminal of application of a supply voltage, said first transistor being in series with a second MOS transistor of the same channel type controlled by an input stage of a transconductance amplifier, a junction point of the first and second transistors defining an output terminal providing the reference voltage, comprising:

a first current source of fixed value connecting said first supply terminal to a gate of the first transistor;

a second current source of fixed value connecting the second transistor to a second terminal of application of the supply voltage;

at least one third MOS transistor of a second channel type connecting the first and second current sources; and

a capacitive element directly connecting said output terminal to a conduction terminal of the third transistor to vary the conduction of the third transistor in case of a variation in the output voltage.

2. The circuit of claim 1 , wherein the third transistor directly connects the gate of the first transistor to the second current source, said capacitive element being in parallel with the second transistor.

3. The circuit of claim 1 , wherein a fourth transistor of the second channel type is interposed between the third transistor and the second current source, said capacitive element connecting said output terminal to the junction point of the third and fourth transistors.

4. The circuit of claim 1 , wherein the circuit is formed with at least two types of transistors which differentiate by their respective gate oxide thicknesses, the first and third transistors being formed with a relatively thin gate oxide with respect to the second transistor.

5. The circuit of claim 3 , wherein the fourth transistor comprises a relatively thick gate oxide.

6. The circuit of claim 1 , wherein the first transistor is sized according to the current capable of being sourced or sunk by the circuits connected to the output terminal.

7. The circuit of claim 1 , wherein the second transistor is sized according to the fixed value of the current sources.

8. The circuit of claim 1 , wherein the second current source is formed of a MOS transistor of the second type biased by a fixed signal.

9. The circuit of claim 8 , wherein the first current source comprises a MOS transistor of the first type.

10. The circuit of claim 1 , for generating a voltage closer to that of the first terminal than to that of the second terminal, wherein the first and second channel types are respectively P and N.

11. The circuit of claim 1 , for generating a voltage closer to that of the second terminal than to that of the first terminal, wherein the first and second channel types are respectively N and P.

12. A circuit for generating a reference voltage comprising:

a first MOS transistor of a first channel type connected to a first power supply terminal;

a second MOS transistor of the first channel type controlled by an input stage, wherein the first transistor is in series with the second transistor and a junction point of the first and second transistors defines an output terminal providing the reference voltage;

a first current source connecting the first power supply terminal to a gate of the first transistor;

a second current source connecting the second transistor to a second power supply terminal;

at least one third MOS transistor of a second channel type connecting the first and second current sources; and

a capacitive element connecting the output terminal to a conduction terminal of the third transistor to vary the conduction of the third transistor in response to a variation in the reference voltage.

13. The circuit of claim 12 , wherein the third transistor directly connects the gate of the first transistor to the second current source.

14. The circuit of claim 12 , further including a fourth transistor of the second channel type connected between the third transistor and the second current source, wherein the capacitive element connects the output terminal to a junction point of the third and fourth transistors.