A wide range differential current switching circuit can operate across a wide range of input currents and across a broad range of frequencies. A first differential current source can include a first transistor and a second transistor. The first transistor receives a switching signal and provides an output current and at output node. The second transistor receives an inverted switching signal, the first transistor and the second transistor coupled to each other at a tail node. A current source provides an input current to the tail node. A third transistor can provide a boost current to the tail node while the first transistor is off.

Systems, methods and apparatus for efficient power control of an RF amplifier for amplification of a constant envelope RF signal are described. A reduction in a size of a pass device of an LDO regulator is obtained by removing the pass device of the LDO regulator from a main current conduction path of the RF amplifier. Power control is provided by varying one or more gate voltages to cascoded transistors of a transistor stack of the RF amplifier according to a power control voltage. Various configurations for controlling the gate voltages are presented by way of a smaller size LDO regulator or by completely removing the LDO regulator. In a case where a supply voltage to the transistor stack varies, such as in a case of a battery, a compensation circuit is used to adjust the power control voltage in view of a variation of the supply voltage, and therefore null a corresponding drift in output power of the RF amplifier.

Apparatus and methods for envelope tracking systems with automatic mode selection are provided herein. In certain configurations, a power amplifier system includes a power amplifier configured to provide amplification to a radio frequency signal and to receive power from a power amplifier supply voltage, and an envelope tracker including a signal bandwidth detection circuit configured to generate a detected bandwidth signal based on processing an envelope signal corresponding to an envelope of the radio frequency signal. The envelope tracker further includes a switch bank configured to receive a plurality of regulated voltages, a filter configured to filter an output of the switch bank to generate the power amplifier supply voltage, and a mode control circuit configured to control a filtering characteristic of the filter based on the detected bandwidth signal.

An LNA having a plurality of paths, each of which can be controlled independently to achieve a gain mode. Each path includes at least an input FET and an output FET coupled in series. A gate of the output FET is controlled to set the gain of the LNA. Signals to be amplified are applied to the gate of the input FET. Additional stacked FETs are provided in series between the input FET and the output FET.

The present disclosure provides a trans-impedance amplifier, comprising: an equivalent secondary amplifier module, having an input end and an output end, wherein the input end is coupled to an optical diode and used for accessing an input voltage signal, and the output end is used for outputting a secondarily amplified first voltage signal; an inverting amplifier unit, coupled to the output end of the equivalent secondary amplifier module and used for accessing the first voltage signal and outputting an inverting amplified voltage signal, the inverting amplifier unit comprising a third N-type transistor and a fourth N-type transistor coupled to the third N-type transistor; and a feedback resistor, coupled to the input end of the equivalent secondary amplifier module and an output end of the inverting amplifier unit. The feedback resistor of the trans-impedance amplifier can be not restricted by original conditions, may increase resistance, reduce input noise and improve sensitivity.

A power amplifier circuit includes a transistor, a bias current source, and an adjustment circuit. The transistor amplifies an RF signal when supplied with a variable power supply voltage. The bias current source supplies a bias current to the base of the transistor through a first current path. The adjustment circuit increases a current flowing from the bias current source to an input terminal of a matching circuit through a second current path as the variable power supply voltage decreases, and decreases the bias current flowing from the bias current source to the base of the transistor through the first current path as the current flowing from the bias current source to the input terminal through the second current path increases.

A circuit is formed on an SOI. The bias generator is connected to the gates of first and second transistors. In the bias generator, a first variable current source is connected to the power supply circuit via a power supply node. A third transistor is connected between the first variable current source and a ground-voltage source. A gate thereof is connected to the gate of the first transistor. A first operational amplifier controls a gate voltage of the third transistor so that a voltage at a second node between the first variable current source and the third transistor becomes almost equal to a reference-voltage. A first characteristics changer is connected to the gate of the third transistor or a second node, to change at least one loop gain characteristics and phase characteristics of a loop from the first operational amplifier, through the third transistor, to the first variable current source.

An amplifier circuit includes: an input circuit configured to receive an input signal; a load circuit provided in series with the input circuit and including a first variable resistance unit and a second variable resistance unit, a resistance value of the first variable resistance unit being controlled by, a digital code, a resistance value of the second variable resistance unit being controlled by an analog control voltage; and a correction circuit including a third variable resistance unit having a circuit configuration corresponding to the first variable resistance unit and a fourth variable resistance unit having a circuit configuration corresponding to the second resistance unit, a resistance value of the third variable resistance unit being controlled by the digital code, a resistance value of the fourth variable resistance unit being controlled by the analog control voltage, the correction circuit being configured correct a resistance value of the load circuit.

Methods and devices for amplifying an input RF signal according to at least two gain-states is described. According to one aspect, a multi gain amplifier circuit including a low noise amplifier having a stack of transistors is used for amplification of the input RF signal. When switching from a low gain-state to a high gain-state, the drain-to-source voltage of the output transistor of the stack is increased to affect region of operation of the output transistor, and thereby reduce non-linearity at the output of the amplifier. When switching from the high gain-state to the low gain-state, the drain-to-source voltage of the input transistor of the stack is increased to affect region of operation of the input transistor, and thereby reduce non-linearity at the output of the amplifier.

An amplifier circuit including a first folded double cascode stage configured to receive a differential input signal at a first pair of input transistors and generate a first drive signal, a second folded double cascode stage configured to receive the differential input signal at a second pair of input transistors and generate a second drive signal, and an output stage. The output stage includes a PMOS common-source output transistor configured to receive the first drive signal at its gate, and an NMOS common-source output transistor configured to receive the first drive signal at its gate, the PMOS common-source output transistor and NMOS common-source output transistor being jointly configured to generate an output signal based on the first drive signal and the second drive signal.