Push-pull amplifier with quiescent current adjuster

An amplification system comprising:

• a push-pull amplifier;
• a feedback line for feeding back a feedback signal from the push-pull amplifier;
• a quiescent current control circuit for receiving the feedback signal and a reference quiescent current signal, and for generating a control signal on the basis of the feedback signal and the reference quiescent current signal;
• and
• a quiescent current adjuster comprising a resistive series connection and a controllable current source arrangement for causing a current through the resistive series connection in response to the control signal, wherein an inner node of the resistive series connection is provided for receiving a signal to be amplified by the push-pull amplifier and wherein two outer terminals of the resistive series connection are connected to control terminals of a first portion and a complementary second portion, respectively, of the push-pull amplifier.

A mobile communication device comprising:

• an antenna port;
• a digital baseband processor;
• and
• an RF-frontend coupled to the antenna port and to the digital baseband processor, and comprising a push-pull amplifier, the push-pull amplifier comprising:
• an input node;
• a series connection of two resistors, the series connection comprising a first terminal, a second terminal, and a third terminal, wherein a first resistor of the two resistors is connected between the first terminal and the second terminal, wherein a second resistor of the two resistors is connected between the second terminal and the third terminal, and wherein the input node is connected to the second terminal;
• a first controllable current source connected between the first terminal of the series connection and a first supply potential node for sourcing a first current to the series connection;
• a second controllable current source connected between the second terminal of the series connection and a second supply potential node for sinking a second current from the series connection, wherein the first and second supply potential nodes are different;
• a first transistor and a second transistor in push-pull configuration, wherein a control input of the first transistor is connected to the first terminal of the series connection and a control input of the second transistor is connected to the third terminal of the series connection,
• wherein the first supply potential node is configured to couple to a first supply potential, and the second supply potential node is configured to couple to a second, different supply potential.

A mobile communication device comprising:

• an antenna port;
• a digital baseband processor;
• and
• an RF-frontend coupled between the antenna port and the digital baseband processor, and comprising an amplification system that comprises:
• a push-pull amplifier;
• a feedback line for feeding back a feedback signal from the push-pull amplifier;
• a quiescent current control circuit for receiving the feedback signal and a reference current signal, and for generating a control signal on the basis of the feedback signal and the reference current signal;
• and
• a quiescent current adjuster comprising a resistive series connection and a controllable current source arrangement for causing a current through the resistive series connection in response to the control signal, wherein an inner node of the resistive series connection is provided for receiving a signal to be amplified by the push-pull amplifier and wherein two outer terminals of the resistive series connection are connected to control terminals of a first portion and a second complementary portion, respectively, of the push-pull amplifier.

A method for amplifying a signal, the method comprising:

• supplying a current to a resistive series connection to generate a first voltage drop over a first resistor and a second voltage drop over a second resistor of the resistive series connection, wherein a node between the first resistor and the second resistor comprises an inner node of the resistive series connection;
• feeding the signal to be amplified to the inner node of a resistive series connection between the first and second resistors to obtain, due to the first and second voltage drops, a first shifted signal and a second shifted signal, respectively, at two outer terminals of the resistive series connection;
• applying the first shifted signal to a first transistor;
• and
• applying the second shifted signal to a second transistor, wherein the first and second transistors are connected in series and form a push-pull configuration;
• wherein the current supplied to the resistive series connection adjusts a quiescent current of the push-pull configuration via the first and second voltage drops.

A method for amplifying a signal, the method comprising:

• receiving a feedback signal from a push-pull amplifier;
• receiving a reference quiescent current signal;
• generating a control signal on the basis of the feedback signal and the reference quiescent current signal;
• applying the control signal and the signal to be amplified to a quiescent current adjuster for obtaining a first shifted version of the signal to be amplified and a second shifted version of the signal to be amplified, wherein an amount by which the first and second shifted versions are offset with respect to the signal to be amplified is determined by the control signal;
• applying the first and second shifted versions to a first transistor and to a second transistor, respectively, in push-pull configuration.