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.

A radio frequency circuit includes a power amplifier configured to selectively amplify one of a first radio frequency signal and a second radio frequency signal that have different bandwidths, and when the first radio frequency signal is input to the power amplifier, a first bias signal is applied to the power amplifier, and when the second radio frequency signal is input to the power amplifier, a second bias signal different from the first bias signal is applied to the power amplifier.

An envelope tracking (ET) voltage tracker circuit is provided. The ET voltage tracker circuit is configured to generate a time-variant voltage based on a time-variant target voltage, which further corresponds to a time-variant power envelope of a radio frequency (RF) signal. The time-variant voltage may be provided to an amplifier circuit(s) for amplifying the RF signal. The ET voltage tracker circuit includes a target voltage processing circuit configured to pre-process the time-variant target voltage. More specifically, the target voltage processing circuit is configured to pre-process the time-variant target voltage based on a high-order transfer function when the time-variant target voltage corresponds to a higher modulation bandwidth (e.g., >80 MHz). As a result, it may be possible to improve temporal alignment between the time-variant voltage and the time-variant target voltage at the amplifier circuit(s), thus allowing the amplifier circuit(s) to operate with improved efficiency and linearity.

A power amplifier arrangement comprises a power amplifier comprising at least one transistor having a first gate and a second gate. The first gate is configured to receive a radio frequency input signal superimposed with a first control signal, and the second gate is configured to receive a second control signal. The first control signal is a linearization signal varying in relation to an envelope of the input signal and the second control signal is a temperature compensation signal varying in relation to a temperature of the power amplifier, or vice versa.

A transmitter is provided. The transmitter includes a bus system including at least two bus lines. Further, the transmitter includes an envelope tracking circuit coupled to the at least two bus lines, and a plurality of power amplifiers. At least a first one of the plurality of power amplifiers, while in active state, is configured to selectively couple its input to the one of the at least two bus lines which is supplied with a supply voltage or a bias signal by the envelope tracking circuit that is based on an envelope of a first baseband signal related to a first radio frequency signal received by the first one of the plurality of power amplifiers for amplification.

A power amplifier circuit includes a transistor having a base to which a radio frequency signal is input and a collector to which a power supply voltage that varies in accordance with an envelope of amplitude of the radio frequency signal is supplied and from which an amplified signal obtained by amplifying the radio frequency signal is output; a first termination circuit provided at a stage subsequent to the transistor and configured to attenuate a harmonic component of the amplified signal; and a second termination circuit provided at the stage subsequent to the transistor and configured to attenuate a harmonic component of the amplified signal. The first termination circuit and the second termination circuit have a property of resonating for a radio frequency signal having a frequency between a frequency of a second harmonic component and a frequency of a third harmonic component.

Charge pump tracker circuitry is disclosed having a first switch network configured to couple a first flying capacitor between a voltage input terminal and a ground terminal during a first charging phase and couple the first flying capacitor between the voltage input terminal and a pump output terminal during a first discharging phase. A second switch network is configured to couple a second flying capacitor between the voltage input terminal and the ground terminal during a second charging phase and couple the second flying capacitor between the voltage input terminal and the pump output terminal during a second discharging phase. A switch controller is configured to monitor first and second voltages across the first and second flying capacitors, respectively, during the first and second discharging phases and in response to control the first and second switch networks so that the first the second discharging phases alternate in an interleaved mode.

Embodiments described herein relate to an envelope tracking system that uses a single-bit digital signal to encode an analog envelope tracking control signal, or envelope tracking signal for brevity. In certain embodiments, the envelope tracking system can estimate or measure the amplitude of the baseband signal. The envelope tracking system can further estimate the amplitude of the envelope of the RF signal. The system can convert the amplitude of the envelope signal to a single-bit digital signal, typically at a higher, oversample rate. The single-bit digital signal can be transmitted in, for example, a low-voltage differential signaling (LVDS) format, from a transceiver to an envelope tracker. An analog-to-digital converter (ADC or A/D) can convert the single-bit digital signal back to an analog envelope signal. Moreover, a driver can increase the power of the A/D output envelope signal to produce an envelope-tracking supply voltage for a power amplifier.

An envelope tracking system for controlling a power amplifier supply voltage includes envelope circuitry and a feed forward digital to analog converter (DAC) circuitry. The envelope circuitry is configured to generate a target envelope signal based on a selected power amplifier supply voltage. The feed forward DAC circuitry includes a voltage source circuitry and a selector circuitry. The voltage source circuitry is configured to generate a plurality of voltages. The selector circuitry is configured to select one of the plurality of voltages based at least on the target envelope signal. The feed forward DAC circuitry is configured to provide the selected voltage to a supply voltage input of a power amplifier that amplifies a radio frequency (RF) transmit signal.

The present disclosure relates to an envelope tracking (ET) amplification architecture, which includes a power amplifier (PA) block configured to amplify a radio frequency (RF) input signal and provide an RF output signal, and an ET voltage block configured to provide modulated voltages to the PA block as power supplies. Herein, the modulated voltages are provided based on a configuration of the PA block and from one pulsed ramp signal, which contains envelope information of the RF input signal. The modulated voltages are eligible to have at least one of a time delay difference, an amplitude difference, and a phase difference.