Amplifier, filter, communication apparatus and network node

1. A differential amplifier, comprising:

a first differential circuitry structure including a first part comprising at least one branch of transistors and a second part comprising at least one branch of transistors; and

a second circuitry structure comprising:

a first non-linear device connected between a signal point of a branch of the first part having a first differential input terminal of the differential amplifier and a common center node of the second circuitry structure; and

a second non-linear device connected between a signal point of a branch of the second part having a second differential input terminal of the differential amplifier and the common center node;

wherein the first non-linear device comprises a transistor having a control node connected to a first differential output terminal of the differential amplifier, wherein the first differential output terminal provides an inverted output in relation to the first differential input terminal; and

wherein the second non-linear device comprises a transistor having a control node connected to a second differential output terminal of the differential amplifier, wherein the second differential output terminal provides an inverted output in relation to the second differential input terminal; and

wherein the common center node is connected to a control node of one of the transistors of the branch of the first part having one of the differential output terminals, and connected to a control node of one of the transistors of the branch of the second part having the other differential output terminal.

2. The differential amplifier of claim 1 :

wherein the first non-linear device comprises a first MOS transistor;

wherein the connection of the first non-linear device to the signal point of the branch of the first part having the first differential input terminal is a connection of a first node of the first MOS transistor, wherein the connection of the first non-linear device to the common center node is a connection of a second node of the first MOS transistor, and

wherein the transistor of the first non-linear device having the control node is the first MOS transistor having its gate connected to one of the differential output terminals; and

the second non-linear device comprises a second MOS transistor;

wherein the connection of the second non-linear device to the signal point of the branch of the second part having the second differential input terminal is a connection of a first node of the second MOS transistor, wherein the connection of the second non-linear device to the common center node is a connection of a second node of the second MOS transistor; and

wherein the transistor of the second non-linear device having the control node is the second MOS transistor having its gate connected to the other differential output terminal.

3. The differential amplifier of claim 2 , wherein the first and second MOS transistors are operated in a triode region.

4. The differential amplifier of claim 1 :

wherein the first part comprises a branch with a cascoded first transistor, and second transistor and biasing circuitry;

wherein the second part comprises a branch of a cascoded third transistor, and fourth transistor and biasing circuitry,

wherein the first and second differential input terminals are provided at control nodes of the first and third transistors, respectively; and

wherein the common center node is connected to control nodes of the second and fourth transistors.

5. The differential amplifier of claim 1 , wherein the differential amplifier is configured as a balanced operational transconductance amplifier.

6. The differential amplifier of claim 5 :

wherein the first part comprises:

a branch comprising an input transistor arrangement for the first differential input terminal and a further transistor; wherein the first non-linear device is connected to the signal point at a point between the input transistor arrangement and the further transistor of that branch; and

another branch comprising a first transistor and a second transistor, wherein the first differential output terminal is provided between the first and second transistors;

wherein the second part comprises:

a branch comprising an input transistor arrangement for the second differential input terminal and a further transistor; wherein the second non-linear device is connected to the signal point at a point between the input transistor arrangement and the further transistor of that branch; and

another branch comprising a first transistor and a second transistor, wherein the second differential output terminal is provided between the first and second transistors; and

wherein the control nodes of the transistors to which the common center node is connected are control nodes of the first transistors of the another branches of the first and second parts.

7. The amplifier of claim 1 , wherein a branch is a series connection of elements between a supply voltage node and a reference voltage node.

8. The amplifier of claim 7 , wherein the reference voltage node is a ground node.

9. A low-noise amplifier, comprising:

a differential amplifier configured as a complementary amplifier, the differential amplifier comprising:

a first differential circuitry structure including a first part comprising at least one branch of transistors and a second part comprising at least one branch of transistors; and

a second circuitry structure comprising:

a first non-linear device connected between a signal point of a branch of the first part having a first differential input terminal of the differential amplifier and a common center node of the second circuitry structure; and

a second non-linear device connected between a signal point of a branch of the second part having a second differential input terminal of the differential amplifier and the common center node;

wherein the first non-linear device comprises a transistor having a control node connected to a first differential output terminal of the differential amplifier, wherein the first differential output terminal provides an inverted output in relation to the first differential input terminal; and

wherein the second non-linear device comprises a transistor having a control node connected to a second differential output terminal of the differential amplifier, wherein the second differential output terminal provides an inverted output in relation to the second differential input terminal; and

wherein the common center node is connected to a control node of one of the transistors of the branch of the first part having one of the differential output terminals, and connected to a control node of one of the transistors of the branch of the second part having the other differential output terminal;

a feedback network connected between inputs and outputs of the differential amplifier.

10. A filter, comprising:

a plurality of differential amplifiers, each of the differential amplifiers comprising:

a first differential circuitry structure including a first part comprising at least one branch of transistors and a second part comprising at least one branch of transistors; and

a second circuitry structure comprising:

a first non-linear device connected between a signal point of a branch of the first part having a first differential input terminal of the differential amplifier and a common center node of the second circuitry structure; and

a second non-linear device connected between a signal point of a branch of the second part having a second differential input terminal of the differential amplifier and the common center node;

wherein the first non-linear device comprises a transistor having a control node connected to a first differential output terminal of the differential amplifier, wherein the first differential output terminal provides an inverted output in relation to the first differential input terminal; and

wherein the second non-linear device comprises a transistor having a control node connected to a second differential output terminal of the differential amplifier, wherein the second differential output terminal provides an inverted output in relation to the second differential input terminal; and

wherein the common center node is connected to a control node of one of the transistors of the branch of the first part having one of the differential output terminals, and connected to a control node of one of the transistors of the branch of the second part having the other differential output terminal.

11. The filter of claim 10 :

wherein the differential amplifiers are configured as operational transconductance amplifiers; and

wherein the filter further comprises one or more biquad structures employing the operational transconductance amplifiers.

12. A power amplifier, comprising:

a driver stage;

wherein the driver stage comprises a differential amplifier, the differential amplifier comprising:

a first differential circuitry structure including a first part comprising at least one branch of transistors and a second part comprising at least one branch of transistors; and

a second circuitry structure comprising:

a first non-linear device connected between a signal point of a branch of the first part having a first differential input terminal of the differential amplifier and a common center node of the second circuitry structure; and

a second non-linear device connected between a signal point of a branch of the second part having a second differential input terminal of the differential amplifier and the common center node;

wherein the first non-linear device comprises a transistor having a control node connected to a first differential output terminal of the differential amplifier, wherein the first differential output terminal provides an inverted output in relation to the first differential input terminal; and

wherein the second non-linear device comprises a transistor having a control node connected to a second differential output terminal of the differential amplifier, wherein the second differential output terminal provides an inverted output in relation to the second differential input terminal; and

wherein the common center node is connected to a control node of one of the transistors of the branch of the first part having one of the differential output terminals, and connected to a control node of one of the transistors of the branch of the second part having the other differential output terminal.

13. A communication apparatus configured to operate in a cellular communication system, the communication apparatus comprising:

radio circuitry;

wherein the radio circuitry comprises a differential amplifier, the differential amplifier comprising:

a first differential circuitry structure including a first part comprising at least one branch of transistors and a second part comprising at least one branch of transistors; and

a second circuitry structure comprising:

a first non-linear device connected between a signal point of a branch of the first part having a first differential input terminal of the differential amplifier and a common center node of the second circuitry structure; and

a second non-linear device connected between a signal point of a branch of the second part having a second differential input terminal of the differential amplifier and the common center node;

wherein the first non-linear device comprises a transistor having a control node connected to a first differential output terminal of the differential amplifier, wherein the first differential output terminal provides an inverted output in relation to the first differential input terminal; and

wherein the second non-linear device comprises a transistor having a control node connected to a second differential output terminal of the differential amplifier, wherein the second differential output terminal provides an inverted output in relation to the second differential input terminal; and

wherein the common center node is connected to a control node of one of the transistors of the branch of the first part having one of the differential output terminals, and connected to a control node of one of the transistors of the branch of the second part having the other differential output terminal.

14. A network node configured to operate in a cellular communication system, the network node comprising:

radio circuitry;

wherein the radio circuitry comprises a differential amplifier, the differential amplifier comprising:

a first differential circuitry structure including a first part comprising at least one branch of transistors and a second part comprising at least one branch of transistors; and

a second circuitry structure comprising:

a first non-linear device connected between a signal point of a branch of the first part having a first differential input terminal of the differential amplifier and a common center node of the second circuitry structure; and

a second non-linear device connected between a signal point of a branch of the second part having a second differential input terminal of the differential amplifier and the common center node;

wherein the first non-linear device comprises a transistor having a control node connected to a first differential output terminal of the differential amplifier, wherein the first differential output terminal provides an inverted output in relation to the first differential input terminal; and

wherein the second non-linear device comprises a transistor having a control node connected to a second differential output terminal of the differential amplifier, wherein the second differential output terminal provides an inverted output in relation to the second differential input terminal; and

wherein the common center node is connected to a control node of one of the transistors of the branch of the first part having one of the differential output terminals, and connected to a control node of one of the transistors of the branch of the second part having the other differential output terminal.