An envelope tracking (ET) amplifier apparatus is provided. The ET amplifier apparatus includes a number of amplifier circuits that can be activated concurrently or selectively for amplifying a number of radio frequency (RF) signals. Notably, some amplifier circuits may amplify RF signals corresponding to a higher modulation bandwidth (e.g., >80 MHz), while other amplifier circuits may amplify RF signals corresponding to a lower modulation bandwidth (e.g., <40 MHz). In examples discussed herein, the ET amplifier apparatus can be flexibly configured to the amplifier circuits, either concurrently or selectively, to amplify the RF signals corresponding to a wide range of modulation bandwidths, without compromising linearity and efficiency of the amplifier circuits. Moreover, the ET amplifier apparatus may be configured to share a common circuit(s) among a number of circuits, thus helping to reduce footprint of the ET amplifier apparatus.

A power amplifier apparatus, includes an envelope tracking (ET) current bias circuit configured to generate a first ET bias current by calculating a direct current DC, based on a reference voltage, and an ET current, based on an ET voltage, according to an envelope of an input signal; and a power amplifier circuit having a bipolar junction transistor supplied with the first ET bias current and a power voltage to amplify the input signal, wherein an average current of the first ET bias current is controlled to be substantially constant.

An envelope tracking (ET) amplifier apparatus is provided. The ET amplifier apparatus includes a number of amplifier circuits that can be activated concurrently or selectively for amplifying a number of radio frequency (RF) signals. Notably, some amplifier circuits may amplify RF signals corresponding to a higher modulation bandwidth (e.g., >80 MHz), while other amplifier circuits may amplify RF signals corresponding to a lower modulation bandwidth (e.g., <40 MHz). In examples discussed herein, the ET amplifier apparatus can be flexibly configured to the amplifier circuits, either concurrently or selectively, to amplify the RF signals corresponding to a wide range of modulation bandwidths, without compromising linearity and efficiency of the amplifier circuits. Moreover, the ET amplifier apparatus may be configured to share a common circuit(s) among a number of circuits, thus helping to reduce footprint of the ET amplifier apparatus.

Certain aspects of the present disclosure generally relate to apparatus and techniques for wireless communication. One example apparatus generally includes an antenna terminal, an amplifier, a matching network coupled between the antenna terminal and an output of the amplifier, a first voltage envelope detector coupled to a node between the antenna and the matching network, and a current detection circuit coupled to the amplifier.

An apparatus of a transmitter and method are provided, the apparatus comprising a processor that calculates a supply voltage (SV) value (SVV) to provide as an SV for a power amplifier (PA) of the transmitter for transmissions during a transmission time slot (TS). When the SV<an envelope tracking (ET) threshold (ETT), then the processor configures the PA to transmit a signal in an average power tracking (APT) mode that maintains the SV at the SVV during the TS. When the SVETT, and an APT condition is met, then the processor configures the PA to transmit the signal in the APT mode. When the SVETT, and the APT condition is not met, then the processor transmits by an adjustment to the SVV to track an amplitude modulation envelope during the TS in an ET mode.

A digital isolator comprising a set of bipolar transistors and an inductor capacitor (LC) oscillator coupled to the set of bipolar transistors in series, wherein the LC oscillator is configured to be turned on and off based on the current applied to the set of bipolar transistors or the LC oscillator and generate a set of differential signals based on the current flowing through the set of bipolar transistors and mimicking the operational characteristics of an optocoupler.

A power amplifier circuit includes a first transistor that amplifies an RF signal; a bias current source that supplies a bias current to a second terminal of the first transistor through a first current path; and an adjustment circuit that adjusts the bias current in accordance with a variable power-supply voltage supplied from a power-supply terminal. The adjustment circuit includes first to third resistors, and an adjustment transistor including a first terminal connected to the power-supply terminal through the first resistor, a second terminal connected to the bias current source through the second resistor, and a third terminal connected to the first current path through the third resistor. When the variable power-supply voltage is not less than a first voltage and not greater than a third voltage, the adjustment circuit increases a current that flows to the power-supply terminal through a second current path as the variable power-supply voltage decreases.

An envelope tracking (ET) circuit is provided. The ET circuit includes an amplifier array(s) configured to amplify a radio frequency (RF) signal(s) based on a first input voltage and a second input voltage. The ET circuit includes a pair of tracker circuits each configured to generate a modulated voltage. Control circuitry couples a selected tracker circuit among the tracker circuits to provide a selected modulated voltage (e.g., ET modulated voltage) to the amplifier array(s) as the first input voltage. Depending on usage scenarios, the control circuitry also provides an ET modulated voltage, an average power tracking (APT) modulated voltage, or a constant voltage to the amplifier array(s) as the second input voltage. As such, the ET circuit can support the RF signal(s) modulated in a wide range of modulation bandwidth without compromising efficiency and/or increasing heat dissipation of the amplifier array(s).

High bandwidth envelope trackers are provided herein. In certain embodiments, an envelope tracking system for a power amplifier includes a switching regulator that operates in combination with a high bandwidth amplifier to generate a power amplifier supply voltage for the power amplifier based on an envelope of a radio frequency (RF) signal amplified by the power amplifier. The high bandwidth amplifier includes an output that generates an output current for adjusting the power amplifier supply voltage, a first input that receives a reference signal, and a second input that receives an envelope signal indicating the envelope of the RF signal. The second input has lower input impedance than the first input to provide a rapid transient response and high envelope tracking bandwidth.

An envelope tracking (ET) amplifier circuit is provided. The ET amplifier circuit includes an ET voltage circuit configured to generate an ET modulated voltage based on a supply voltage for amplifying a radio frequency (RF) signal. The ET modulated voltage corresponds to a time-variant voltage envelope, which can be misaligned from a time-variant signal envelope of the RF signal due to an inherent temporal delay in the ET amplifier circuit. A voltage processing circuit is provided in the ET amplifier circuit to reduce dynamic range of the ET modulated voltage to help improve delay sensitivity in the ET amplifier circuit. A control circuit is configured to reduce the supply voltage according to the dynamic range to help maintain system-wide efficiency of the ET amplifier circuit at a defined level. As such, it may be possible to improve delay sensitivity and maintain sufficient system-wide efficiency in the ET amplifier circuit.