An envelope tracking (ET) integrated circuit (ETIC) operable with multiple types of power amplifiers is provided. The ETIC is configured to provide one or more ET voltages to a power amplifier(s) for amplifying a radio frequency (RF) signal. In embodiments disclosed herein, the ETIC can be configured to generate the ET voltages at same or different voltage levels based on specific types of the power amplifier(s), such as multi-stage power amplifier and Doherty power amplifier, and for a wider modulation bandwidth of the RF signal. As such, the ETIC can be flexibly adapted to enable a variety of power management scenarios and/or topologies.

In some embodiments, an amplifier system can include an amplifier circuit having first and second amplifiers configured to amplify respective first and second portions of an input signal. Each of the first and second amplifiers can include a cascode stage with input and output transistors arranged in a cascode configuration. The amplifier system can further include an envelope tracking bias circuit coupled to the amplifier circuit and configured to provide a bias signal to the output transistor of the cascode stage of at least one of the first and second amplifiers. The amplifier system can further include a supply circuit configured to provide a non-envelope tracking supply voltage to the output transistor of the cascode stage of the at least one of the first and second amplifiers.

A wideband transmission circuit is provided. The wideband transmission circuit includes a transceiver circuit and a power amplifier circuit(s). The transceiver circuit generates a radio frequency (RF) signal(s) from a time-variant input vector and provides the RF signal(s) to the power amplifier circuit(s). The power amplifier circuit(s) amplifies the RF signal(s) based on a modulated voltage and provides the amplified RF signal(s) to a coupled RF front-end circuit (e.g., filter/multiplexer circuit). In embodiments disclosed herein, the transceiver circuit is configured to apply an equalization filter to the time-variant input vector to thereby compensate for a voltage distortion filter caused by a coupling of the power amplifier circuit(s) and the RF front-end circuit. As a result, it is possible to reduce undesired instantaneous excessive compression and/or spectrum regrowth resulting from the voltage distortion filter to thereby improve efficiency and linearity of the power amplifier circuit(s).

Various envelope tracking amplifiers are presented that can be switched between an ET (envelope tracking) mode and a non-ET mode. Switches and/or tunable components are utilized in constructing the envelope tracking amplifiers that can be switched between the ET mode and the non-ET mode.

An envelope tracking (ET) power amplifier circuit is disclosed. The ET power amplifier circuit includes ET tracker circuitry configured to output an ET modulated output voltage having an output voltage envelope that tracks a target voltage envelope of an ET modulated target voltage. Impedance adjustment circuitry in the ET power amplifier circuit is provided between a first node and a second node coupled to a feedback voltage input and a voltage output of the ET tracker circuitry, respectively. A power amplifier circuit(s) includes a first amplifier and a second amplifier coupled respectively to the first node and the second node. As such, it is possible to configure the impedance adjustment circuitry to provide adjustment impedance to offset output impedance of the ET tracker circuitry, thus helping to reduce voltage error in the ET power amplifier circuit.

A multi-mode envelope tracking (ET) amplifier circuit is provided. The multi-mode ET amplifier circuit can operate in a low-resource block (RB) mode, a mid-RB mode, and a high-RB mode. The multi-mode ET amplifier circuit includes fast switcher circuitry having a first switcher path and a second switcher path and configured to generate an alternating current (AC) current. A control circuit activates the fast switcher circuitry in the mid-RB mode and the high-RB mode, while deactivating the fast switcher circuitry in the low-RB mode. More specifically, the control circuit selectively activates one of the first switcher path and the second switcher path in the mid-RB mode and activates both the first switcher path and the second switcher path in the high-RB mode. As a result, it is possible to improve efficiency of ET tracker circuitry and the multi-mode ET amplifier circuit in all operation modes.

An amplifier apparatus (332) comprises a main linear amplifier sub-circuit (402) having a main driving signal input terminal (331) and a main amplifier output terminal (406). The apparatus also comprises an auxiliary linear amplifier sub-circuit (404) having an auxiliary driving signal input terminal (357) and an auxiliary amplifier output terminal (408). A combining network (410) is operably coupled between the main amplifier output terminal (406) and the auxiliary amplifier output terminal (408), the combining network (410) having a main-side terminal (424) and an auxiliary-side terminal (434). The main linear amplifier sub-circuit (402) is arranged to generate, when in use, a main amplified signal in response to a main driving signal applied at the main driving signal input terminal (331). The auxiliary linear amplifier sub-circuit (404) is arranged to generate, when in use, an impedance modifying signal at the auxiliary-side terminal (357) in response to an auxiliary driving signal and at substantially the same time as the main linear amplifier sub-circuit (402) generates the main amplified signal, the auxiliary linear amplifier sub-circuit (404) also being arranged to amplify substantially more than half of each wave cycle of the auxiliary driving signal.

This application relates to audio driving circuits having good audio performance. The circuit (301) has a forward signal path between an input (103) for receiving an input audio signal (S.sub.IN) and an output (104) for outputting an output signal (S.sub.OUT) with an amplifier module (102) in the forward signal path. An error block (302) is arranged to receive a first signal (S.sub.FF) derived from the input signal and also a second signal (S.sub.FB) derived from the output signal and determine a first error signal (.sub.1) indicative of a difference between the first and second signals. A first processing module (204) is operable to generate a compensation signal (S.sub.C) to be applied to the input signal (S.sub.IN) upstream of the amplifier module (102) based on the first error signal. The error block (302) comprises a second processing module (303/303a) configured to apply a linear transfer function to one of the first signal or the second signals prior to determining the first error signal. In some embodiments the second processing module may apply a linear transfer function which is adaptive based on a second error signal (.sub.2) indicative of the error between the first and second signals after the linear transfer function has been applied.

This application relates to methods and apparatus for amplification of audio signals with improved audio performance. An audio driving circuit (200) has an amplifier module (102) in a forward signal path between an input (103) for receiving an input audio signal (S.sub.IN) and an output for outputting an audio driving signal (V.sub.OUT). A pre-distortion module (202) is operable to apply a first transfer function to the signal in the forward signal path upstream of the amplifier module, wherein the first transfer function comprises a non-linear distortion function based on at least one distortion setting. An error block (203) is arranged to receive a first signal (S.sub.FF) derived from the input signal and a second signal (S.sub.FB) indicative of the voltage of the audio driving signal and determine a first error signal (.sub.1) indicative of a difference between the first and second signals. The pre-distortion module (202) is operable to control the distortion setting(s) based on the first error signal.

There is disclosed a method of controlling an envelope tracking amplification stage comprising an envelope modulated power supply, the method comprising: determining a shaping function to be applied to an envelope signal for controlling the envelope modulated power supply in dependence on a system linearity objective in a region of operation of the amplifier in which the output power of the amplifier is dependent upon the supply voltage; and determining a pre-distortion function to be applied to an input signal to be amplified in dependence on a further linearity objective of the system, in a region of operation of the amplifier in which the output of the amplifier is dependent upon the input power to the amplifier.