An amplifier includes a first differential input pair of transistors having a first input terminal, a second input terminal, a first output terminal, and a second output terminal. A second differential input pair of transistors has a third input terminal, a fourth input terminal, a third output terminal, and a fourth output terminal. The first input terminal is coupled to the third input terminal, the second input terminal is coupled to the fourth input terminal, the first output terminal is coupled to the third output terminal, and the second output terminal is coupled to the fourth output terminal. A cross-over circuit has a control input coupled to the second fourth input terminals. The cross-over circuit is configured to vary an amount of bias current through the second differential input pair of transistors based on a magnitude of a voltage on the second and fourth input terminals.

Cross-coupling of switched-capacitor output common-mode feedback capacitors in dynamic residue amplifiers is provided via a cross-coupled amplifier, comprising: a current source connected to a first node; a feedback capacitor connected to the first node and a second node; a feedback resistor connected between the second node and ground; an amplifier having an input connected to the second node; a gain transistor having: a drain connected to the first node; a source connected to ground; and a gate connected to an output of the amplifier; and a load capacitor connected to the first node and ground.

A circuit includes a single-ended amplifier having first and second transistors and an amplifier output. The first transistor has a first control input and first and second current terminals. The second transistor has a second control input and third and fourth current terminals. The first and third current terminals are coupled to an adaptively regulated voltage terminal. The circuit also includes a chopper circuit coupled to the amplifier output and to the first and second transistors. A voltage tracking circuit has a voltage tracking circuit input and a voltage tracking circuit output. The voltage tracking circuit input is coupled to the amplifier output, and the voltage tracking circuit output is coupled to the adaptively regulated voltage terminal. The voltage tracking circuit is configured to adaptively vary a voltage on the regulated voltage terminal based on the amplifier output.

A voltage-to-current converter circuit comprises an amplifier, a resistor, first and second feedback circuits, and an output circuit. The amplifier is configured to receive a differential input voltage signal. The resistor is coupled between first and second nodes of the amplifier. The first feedback circuit is coupled to a third node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a first range, and is turned off otherwise. The second feedback circuit is coupled to a fourth node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a second range different from the first range, and is turned off otherwise. The output circuit produces a differential current output signal having a value according to the value of the input voltage signal.

An amplifier circuit comprises a first unit circuit and a second unit circuit. The first unit circuit may include a first current mirror circuit that includes a first active inductor including a P-channel transistor, and a first input circuit configured to generate a first differential current and a second differential current based on a pair of differential input signals. The second unit circuit may include a second current mirror circuit that includes a second active inductor including a P-channel transistor, and a second input circuit configured to generate a third differential current and a fourth differential current based on the pair of differential input signals.

A voltage-to-current converter circuit comprises an amplifier, a resistor, first and second feedback circuits, and an output circuit. The amplifier is configured to receive a differential input voltage signal. The resistor is coupled between first and second nodes of the amplifier. The first feedback circuit is coupled to a third node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a first range, and is turned off otherwise. The second feedback circuit is coupled to a fourth node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a second range different from the first range, and is turned off otherwise. The output circuit produces a differential current output signal having a value according to the value of the input voltage signal.

A voltage-to-current converter circuit comprises an amplifier, a resistor, first and second feedback circuits, and an output circuit. The amplifier is configured to receive a differential input voltage signal. The resistor is coupled between first and second nodes of the amplifier. The first feedback circuit is coupled to a third node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a first range, and is turned off otherwise. The second feedback circuit is coupled to a fourth node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a second range different from the first range, and is turned off otherwise. The output circuit produces a differential current output signal having a value according to the value of the input voltage signal.

An RF amplifier for implementation in SiGe HBT technology is described. The RF amplifier has a cascode stage comprising a common base (CB) transistor and a common emitter (CE) transistor arranged in series between a first voltage rail and a second voltage rail. An RF input is coupled to the base of the CE transistor and an RF output is coupled to the collector of the CB transistor. The RF amplifier includes a CB power-down circuit arranged between the base of the CB transistor and the second voltage rail and a CE power-down circuit arranged between the base of the CE transistor and the second voltage rail. In a power-down mode the CE power-down circuit couples the base of the common-emitter-transistor to the second voltage rail. The CB power-down mode circuit couples the base of the CB transistor to the second voltage rail via a high-ohmic path.

A voltage-to-current converter circuit comprises an amplifier, a resistor, first and second feedback circuits, and an output circuit. The amplifier is configured to receive a differential input voltage signal. The resistor is coupled between first and second nodes of the amplifier. The first feedback circuit is coupled to a third node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a first range, and is turned off otherwise. The second feedback circuit is coupled to a fourth node of the amplifier, provides feedback to the first and second nodes when the value of the input voltage signal is in a second range different from the first range, and is turned off otherwise. The output circuit produces a differential current output signal having a value according to the value of the input voltage signal.

A low noise amplifier circuit includes an input stage circuit, a first output stage circuit, and a second output stage circuit. The input stage circuit is configured to receive an input signal and to generate a bias signal. The first output stage circuit corresponding to a first wireless communication and is configured to be biased according to the bias signal and a first control signal, in order to generate a first output signal, in which the first control signal is for setting a first gain of the first output stage circuit. The second output stage circuit corresponding to a second wireless communication and is configured to be biased according to the bias signal and a second control signal, in order to generate a second output signal, in which the second control signal is for setting a second gain of the second output stage circuit.