Amplification circuit having optimization of power

1. Power amplifier circuit comprising an input, an output comprising:

means for sensing an input voltage;

a set of n cascode circuits, each comprising a first transistor having a gate, a source and a drain terminal and further comprising a second transistor having gate, source and drain terminal; the source and gate of the first transistor of said cascode circuits being respectively connected to a first reference voltage and to receive the input signal, the drain of said first transistor being connected to the source of said second transistor, the drain of which being coupled to said output; and

a control circuit receiving the input voltage sensed by said sensing means for generating a set of control signals which are transmitted to the gates of the second transistors of said n cascode circuits;

wherein the means for sensing the input voltage comprises:

an additional cascode circuit in communication with the first reference voltage and the input signal; and

a passive circuit in communication with the additional cascode circuit and a second reference voltage;

so as to activate or deactivate some of said n cascode circuits and adapt the size of the transistors to the output power to issue to a load.

2. Power amplifier circuit according to claim 1 wherein each of said second transistor is biased, when activated by said control circuit, in class AB showing a quiescent current Iq.

3. Power amplifier circuit according to claim 1 wherein:

the additional cascode circuit comprises a first transistor having a gate, a source and a drain terminal and a second transistor having gate, source and drain terminal; the source and gate of the first transistor of said cascode circuits being respectively connected to the first reference voltage and to receive the input signal, the drain of said first transistor being coupled to the source of said second transistor, and

the passive circuit is coupled between the second reference voltage and the drain of said second transistor of said additional cascode circuit, said passive circuit comprising two resistors mounted as a voltage divider and, in parallel, one capacitor for averaging the RF signal sensed by said sensing means.

4. Power amplifier circuit according to claim 3 wherein the voltage across one of said resistors is transmitted to one input of said control circuit so as to determine the magnitude of the input signal to be amplified and, therefore, the number of cascode elements to activate/deactivate.

5. Power amplifier circuit according to claim 1 wherein it is used for embodying a Radio Frequency amplifier.

6. Power amplification circuit according to claim 1 wherein it is used in a mobile telephone.

7. Power amplification circuit comprising

a first MOS transistor biased in class AB amplification, having a gate, source and drain terminal, the source being connected to the ground and the gate being coupled to receive an input signal; and

a second MOS transistor biased in class A, having a gate, source and drain terminals, the source being connected to the ground and the gate being coupled to receive the input signal;

wherein said first and said second MOS transistors are coupled together by drains and sources to generate the output current to drive the load of said power amplification circuit; and

the first MOS transistor comprises a higher area than the second MOS transistor and a lower biasing point than the second MOS transistor; and

whereby when the input signal increases the Class AB contribution increases while Vout from Class A decreases (compression), thus smoothing the total gain of said power amplification circuit.

8. Power amplification circuit according to claim 7 wherein it further comprises a third transistor mounted as a cascode transistor on the top of both first and second transistors, said cascode transistor having its source connected to the drains of said first and second transistors and a drain coupled to the output of said amplifier.

9. Power amplification circuit according to claim 7 wherein it is used for embodying a RF amplification for wireless mobile telecommunications.

10. Mobile equipment comprising one amplification circuits as defined in claim 1 .

11. Power amplifier circuit comprising an input, an output comprising:

means for sensing an input voltage;

a set of n cascode circuits, each comprising a first transistor having a gate, a source and a drain terminal and further comprising a second transistor having gate, source and drain terminal; the source and gate of the first transistor of said cascode circuits being respectively connected to a first reference voltage and to receive the input signal, the drain of said first transistor being connected to the source of said second transistor, the drain of which being coupled to said output; and

a control circuit receiving the input voltage sensed by said sensing means for generating a set of control signals which are transmitted to the gates of the second transistors of said n cascode circuits;

wherein the sensing means comprises:

an additional cascode circuit comprising a first transistor having a gate, a source and a drain terminal and a second transistor having gate, source and drain terminal; the source and gate of the first transistor of said cascode circuits being respectively connected to the first reference voltage and to receive the input signal, the drain of said first transistor being coupled to the source of said second transistor, and

a passive circuit coupled between a second reference voltage and the drain of said second transistor of said additional cascode circuit, said passive circuit comprising two resistors mounted as a voltage divider and, in parallel, one capacitor for averaging the RF signal sensed by said sensing means;

so as to activate or deactivate some of said n cascode circuits and adapt the size of the transistors to the output power to issue to a load.

12. Power amplifier circuit comprising an input, an output comprising:

means for sensing an input voltage;

a set of n cascode circuits, each comprising a first transistor having a gate, a source and a drain terminal and further comprising a second transistor having gate, source and drain terminal; the source and gate of the first transistor of said cascode circuits being respectively connected to a first reference voltage and to receive the input signal, the drain of said first transistor being connected to the source of said second transistor, the drain of which being coupled to said output; and

a control circuit receiving the input voltage sensed by said sensing means for generating a set of control signals which are transmitted to the gates of the second transistors of said n cascode circuits;

wherein the sensing means comprises:

an additional cascode circuit comprising a first transistor having a gate, a source and a drain terminal and a second transistor having gate, source and drain terminal; the source and gate of the first transistor of said cascode circuits being respectively connected to the first reference voltage and to receive the input signal, the drain of said first transistor being coupled to the source of said second transistor, and

a passive circuit coupled between a second reference voltage and the drain of said second transistor of said additional cascode circuit, said passive circuit comprising two resistors mounted as a voltage divider and, in parallel, one capacitor for averaging the RF signal sensed by said sensing means; and

the voltage across one of said resistors is transmitted to one input of said control circuit so as to determine the magnitude of the input signal to be amplified and, therefore, the number of cascode elements to activate/deactivate;

so as to activate or deactivate some of said n cascode circuits and adapt the size of the transistors to the output power to issue to a load.