Certain aspects of the present disclosure provide methods and apparatus for generating an envelope tracking power supply voltage. For example, certain aspects of the present disclosure provide an envelope tracking power supply having a linear amplifier having an output coupled to a power supply node of an amplifier, wherein a power supply node of the linear amplifier is coupled to a first voltage supply node. The envelope tracking power supply may also include a switch mode power supply having an output coupled to the power supply node of the amplifier. Certain aspects also include a circuit having a first switch coupled to the first voltage supply node and a second switch coupled to a second voltage supply node, wherein a power supply node of the switch mode power supply is coupled to the first switch and the second switch.

A power amplifier circuit includes a first transistor, a second transistor, a first bias circuit supplying a first bias current or voltage, a second bias circuit supplying a second bias current or voltage, a first inductor, and a first capacitor. A power supply voltage is supplied to a collector of the first transistor, and an emitter thereof is grounded. A radio frequency signal and the first bias current or voltage are supplied to a base of the first transistor. The power supply voltage is supplied to a collector of the second transistor, and an emitter thereof is connected to the collector of the first transistor via the first capacitor and is grounded via the first inductor. The second bias current or voltage is supplied to a base of the second transistor. An amplified radio frequency signal is output from the collector of the second transistor.

A power amplifier circuit includes a first transistor, a second transistor, a first bias circuit supplying a first bias current or voltage, a second bias circuit supplying a second bias current or voltage, a first inductor, and a first capacitor. A power supply voltage is supplied to a collector of the first transistor, and an emitter thereof is grounded. A radio frequency signal and the first bias current or voltage are supplied to a base of the first transistor. The power supply voltage is supplied to a collector of the second transistor, and an emitter thereof is connected to the collector of the first transistor via the first capacitor and is grounded via the first inductor. The second bias current or voltage is supplied to a base of the second transistor. An amplified radio frequency signal is output from the collector of the second transistor.

A control circuit includes a first output unit configured to output a constant bias current for setting an electrical bias state of a bias circuit to the bias circuit; a second output unit configured to output a bias control current or constant voltage for controlling the electrical bias state of the bias circuit to the bias circuit; a resistor having one end connected to a reference potential; and a switch provided between another end of the resistor and an output terminal of the second output unit.

A control circuit includes a first output unit configured to output a constant bias current for setting an electrical bias state of a bias circuit to the bias circuit; a second output unit configured to output a bias control current or constant voltage for controlling the electrical bias state of the bias circuit to the bias circuit; a resistor having one end connected to a reference potential; and a switch provided between another end of the resistor and an output terminal of the second output unit.

Hybrid power amplifier circuits, modules, or systems, and methods of operating same, are disclosed herein. In one example embodiment, a hybrid power amplifier circuit includes a preliminary stage amplification device, a final stage amplification device, and intermediate circuitry at least indirectly coupling the preliminary stage amplification device and the final stage amplification device. The intermediate circuitry includes a low-pass circuit and a high-pass circuit, and the hybrid power amplifier circuit is configured to amplify a first signal component at a fundamental frequency. Due at least in part to the intermediate circuitry, a phase of a second signal component at a harmonic frequency that is a multiple of the fundamental frequency is shifted.

Hybrid power amplifier circuits, modules, or systems, and methods of operating same, are disclosed herein. In one example embodiment, a hybrid power amplifier circuit includes a preliminary stage amplification device, a final stage amplification device, and intermediate circuitry at least indirectly coupling the preliminary stage amplification device and the final stage amplification device. The intermediate circuitry includes a low-pass circuit and a high-pass circuit, and the hybrid power amplifier circuit is configured to amplify a first signal component at a fundamental frequency. Due at least in part to the intermediate circuitry, a phase of a second signal component at a harmonic frequency that is a multiple of the fundamental frequency is shifted.

A solid-state semiconductor guitar amplifier system/method mimicking the audio performance characteristics of conventional vacuum tube guitar amplifiers is disclosed. The disclosed system/method incorporates solid-state semiconductor circuitry implementing an input audio preamplifier (IAP) having asymmetric gain control (AGC) that feeds wave shape transformer (WST) circuitry implementing a piecewise/diode breakpoint (PDB) transform that emulates a conventional vacuum tube voltage-current transfer (VIT) characteristic. A breakpoint threshold controller (BTC) determines the offset associated with application of the PDB operation to the audio signal. Once the PDB transform has been applied to the audio signal, it is further processed by pick attack sag compressor (PAC) circuitry that applies positive sag control (PSC) and negative sag control (NSC) compression envelopes to the overall signal shape before presenting the resulting peak compressed signal through an audio volume control (AVC) and conventional solid-state semiconductor speaker power amplifier (SPA) for application to an audio speaker.

A solid-state semiconductor guitar amplifier system/method mimicking the audio performance characteristics of conventional vacuum tube guitar amplifiers is disclosed. The disclosed system/method incorporates solid-state semiconductor circuitry implementing an input audio preamplifier (IAP) having asymmetric gain control (AGC) that feeds wave shape transformer (WST) circuitry implementing a piecewise/diode breakpoint (PDB) transform that emulates a conventional vacuum tube voltage-current transfer (VIT) characteristic. A breakpoint threshold controller (BTC) determines the offset associated with application of the PDB operation to the audio signal. Once the PDB transform has been applied to the audio signal, it is further processed by pick attack sag compressor (PAC) circuitry that applies positive sag control (PSC) and negative sag control (NSC) compression envelopes to the overall signal shape before presenting the resulting peak compressed signal through an audio volume control (AVC) and conventional solid-state semiconductor speaker power amplifier (SPA) for application to an audio speaker.

Metal pillars are placed adjacent to transistor arrays in the power amplifiers that can be used in wireless devices. By placing the metal pillars in intimate contact with the silicon substrate and not over a substantial portion of the transistor arrays, the heat generated by the transistor arrays flows down into the silicon substrate and out the metal pillar. The metal pillar forms a solder bump of a flip chip power amplifier die, which when soldered to a module, further conducts the heat away from the transistor array.