Bias schemes for cascode power amplifiers are disclosed. In certain embodiments, a power amplifier system includes a cascode power amplifier powered by a first supply voltage and that amplifies a radio frequency input signal, and a bias circuit including a voltage regulator that generates a regulated voltage and is powered by the first supply voltage. The bias circuit further includes a bias voltage generation circuit that receives the regulated voltage and generates at least one cascode bias voltage for the cascode power amplifier, a switch that gates a second supply voltage to generate a gated supply voltage, a bias current generation circuit that controls a bias current of the cascode power amplifier and is powered by the gated supply voltage, and a gating circuit that controls the switch based on the regulated voltage and the second supply voltage.

An amplifier includes a semiconductor die and a substrate that is distinct from the semiconductor die. The semiconductor die includes a III-V semiconductor substrate, a first RF signal input terminal, a first RF signal output terminal, and a transistor (e.g., a GaN FET). The transistor has a control terminal electrically coupled to the first RF signal input terminal, and a current-carrying terminal electrically coupled to the first RF signal output terminal. The substrate includes a second RF signal input terminal, a second RF signal output terminal, circuitry coupled between the second RF signal input terminal and the second RF signal output terminal, and an electrostatic discharge (ESD) protection circuit. The amplifier also includes a connection electrically coupled between the ESD protection circuit and the control terminal of the transistor. The substrate may be another semiconductor die (e.g., with a driver transistor and/or impedance matching circuitry) or an integrated passive device.

A bias circuit includes a mirror current source and a current-to-voltage converter. A first terminal of the mirror current source is connected to a supply voltage terminal, a second terminal of the mirror current source is connected to a reference voltage terminal, and a third terminal of the mirror current source is connected to the current-to-voltage converter. A mirror current source is configured to acquire a supply voltage transmitted at the supply voltage terminal through the first terminal, acquire a reference voltage transmitted at the reference voltage terminal through the second terminal, and regulate the supply voltage by using the reference voltage and a preset parameter to obtain a mirror current corresponding to the supply voltage. The preset parameter is parameter information of the mirror current source. The current-to-voltage converter is configured to convert the mirror current into a voltage to provide a bias voltage based on the voltage.

Amplifier circuits, radio communication circuits, radio communication devices, and methods provided in this disclosure provide an amplifier circuit. The amplifier circuit may include an amplifier configured to amplify an input signal to provide an output signal. The amplifier circuit may further include an amplifier stack including a first transistor coupled to the amplifier. The amplifier stack may be configured to receive the output signal to amplify the output signal. The amplifier stack may be configured to receive an input control signal to control the first transistor based on an envelope of the input signal.

Methods and devices used in mobile receiver front end to support multiple paths and multiple frequency bands are described. The presented devices and methods provide benefits of scalability, frequency band agility, as well as size reduction by using one low noise amplifier per simultaneous outputs. Based on the disclosed teachings, variable gain amplification of multiband signals is also presented.

An apparatus for detecting difference in operating characteristics of a main circuit by using a replica circuit is presented. In one exemplary case, a sensed difference in operating characteristics of the two circuits is used to drive a tuning control loop to minimize the sensed difference. In another exemplary case, several replica circuits of the main circuit are used, where each is isolated from one or more operating variables that affect the operating characteristic of the main circuit. Each replica circuit can be used for sensing a different operating characteristic, or, two replica circuits can be combined to sense a same operating characteristic.

Systems, methods and apparatus for practical realization of an integrated circuit comprising a stack of transistors operating as an RF amplifier are described. As stack height is increased, capacitance values of gate capacitors used to provide a desired distribution of an RF voltage at the output of the amplifier across the stack may decrease to values approaching parasitic/stray capacitance values present in the integrated circuit which may render the practical realization of the integrated circuit difficult. Coupling of an RF gate voltage at the gate of one transistor of the stack to a gate of a different transistor of the stack can allow for an increase in the capacitance value of the gate capacitor of the different transistor for obtaining an RF voltage at the gate of the different transistor according to the desired distribution.

An RF amplifier comprises a first ‘transconductance’ transistor (N.sub.CS) arranged to receive an RF input voltage (RFIN) at its gate terminal. A second ‘cascode’ transistor (N.sub.CG) has its source terminal connected to the drain terminal of the first transistor (N.sub.CS) at a node (MID). A feedback circuit portion is configured to measure a node voltage at the node (MID), to determine an average of the node voltage, to compare said average node voltage to a predetermined reference voltage (V.sub.BCG), and to generate a control voltage (CGGATE) dependent on the difference between the average node voltage and the predetermined reference voltage (V.sub.BCG). The feedback circuit portion applies the control voltage (CGGATE) to the gate terminal of the second transistor (N.sub.CG).

A monolithic integrated circuit (IC), and method of manufacturing same, that includes all RF front end or transceiver elements for a portable communication device, including a power amplifier (PA), a matching, coupling and filtering network, and an antenna switch to couple the conditioned PA signal to an antenna. An output signal sensor senses at least a voltage amplitude of the signal switched by the antenna switch, and signals a PA control circuit to limit PA output power in response to excessive values of sensed output. Stacks of multiple FETs in series to operate as a switching device may be used for implementation of the RF front end, and the method and apparatus of such stacks are claimed as subcombinations. An iClass PA architecture is described that dissipatively terminates unwanted harmonics of the PA output signal. A preferred embodiment of the RF transceiver IC includes two distinct PA circuits, two distinct receive signal amplifier circuits, and a four-way antenna switch to selectably couple a single antenna connection to any one of the four circuits.

A transistor stack can include a combination of floating and body tied devices. Improved performance of the RF amplifier can be obtained by using a single body tied device as the input transistor of the stack, or as the output transistor of the stack, while other transistors of the stack are floating transistors. Transient response of the RF amplifier can be improved by using all body tied devices in the stack.