A PA power supply, which includes a first ET power supply, power supply control circuitry, a first PMOS switching element, and a second PMOS switching element, is disclosed. During a first operating mode, the power supply control circuitry selects an OFF state of the first PMOS switching element, selects an ON state of the second PMOS switching element, and adjusts a voltage of a first switch control signal to maintain the OFF state of the first PMOS switching element using a voltage at a source of the first PMOS switching element and a voltage at a drain of the first PMOS switching element; the PA power supply provides a first PA power supply signal; and the first ET power supply provides a first ET power supply signal, such that the first PA power supply signal is based on the first ET power supply signal.

Power amplification units and methods are provided, which use a combiner and an auxiliary signal to feed the power amplifier (PA) with a signal that prevents or reduces operation of higher amplification stages during off periods of the received RF signal. The PA output is delivered through an output matching circuit configured to pass the RF signal and attenuate the auxiliary signal; and the combiner combines the RF signal and the auxiliary signal through respective filters to generate the RF input signal to the PA. An auxiliary signal generator may be configured to generate the auxiliary signal with relation to the RF signal as having a frequency spectrum lower than a cutoff RF frequency. Resulting lower power consumption, particularly in case of low duty cycle RF signals, reduces heating, enables longer battery use and increases reliability performance.

A switching system is connected to the power amplifier of an RF system. The switching system can switch the DC supply voltage to the power amplifier while handling the high DC current and the nanosecond switching speed requirements that are mandatory for most RF systems. The embodiments can rapidly control DC voltages but not interfere with the optimized operation of the RF transistor. The embodiments provide a desired sharp turn-on leading edge for an RF pulse while eliminating the extremely long and undesirable ramp down that typically occurs beyond the desired RF pulse period.

An electronic device is provided. The electronic device includes an earphone including a first impedance component, a signal generator configured to output a first alternating current (AC) signal, a first circuit including at least one first analog device having an impedance component electrically coupled to the first impedance component, and configured to receive the first AC signal and output a first detection signal including a voltage component corresponding to the first impedance component, and at least one processor configured to generate at least one piece of biometric information, based on the first detection signal, and output the at least one piece of biometric information.

A power amplifier module includes an amplifier transistor and a bias circuit. A first power supply voltage based on a first operation mode or a second power supply voltage based on a second operation mode is supplied to the amplifier transistor. The amplifier transistor receives a first signal and outputs a second signal obtained by amplifying the first signal. The bias circuit supplies a bias current to the amplifier transistor. The bias circuit includes first and second resistors and first and second transistors. The first transistor is connected in series with the first resistor and is turned ON by a first bias control voltage which is supplied when the first operation mode is used. The second transistor is connected in series with the second resistor and is turned ON by a second bias control voltage which is supplied when the second operation mode is used.

A bias circuit includes a bias current circuit varying a resistance value according to a mode voltage determined according to a magnitude of an input radio frequency signal, and generating a bias current that is controlled according to the variation of the resistance value; a bias voltage circuit generating a bias voltage that is adjusted according to a change in a power source voltage and supplying the bias voltage to an amplifying circuit; and a bias transfer circuit supplying the bias current to a base node of the amplifying circuit and blocking an input of the radio frequency signal from the base node.

A multi-stage radio frequency power amplifier (RFPA) includes an output stage SMPA and a driver stage SMPA. As the multi-stage RFPA operates, the magnitude of an RF switch drive signal generated by the driver stage SMPA is dynamically minimized based on I-V characteristic curves of the output stage SMPA's power transistor and the output stage SMPA's dynamically changing load line. By constraining the magnitude of the RF switch drive signal as the multi-stage RFPA operates, VGS feedthrough of the RF switch drive signal is minimized, to the extent possible. Amplitude distortion and phase distortion in the RF output that might occur due to unconstrained VGS feedthrough, particularly at low output RF power levels, are therefore avoided. Operating all stages of the multi-stage RFPA in switch mode also results in high energy efficiency and an output RF spectrum with very low wideband noise (WBN).

A power amplifier circuit includes a first transistor having a base to which a radio frequency (RF) signal is supplied and a collector to which a variable power-supply voltage corresponding to a level of the RF signal is supplied, and being configured to amplify the RF signal; a bias circuit including a second transistor configured to supply a bias current to the base of the first transistor; and an adjustment circuit configured to cause the bias current to be supplied to the base of the first transistor to decrease with decrease in the variable power-supply voltage by causing a current to be supplied to a base of the second transistor to decrease.

A radio frequency (RF) front-end circuit is provided. A power management circuit is configured to output a first modulated voltage, a second modulated voltage, a first bias voltage, and a second bias voltage via a first voltage port(s), a second voltage port(s), a first bias voltage port(s), and a second bias voltage port(s), respectively. An amplifier circuit(s) is configured to amplify an RF signal based on a selected modulated voltage and a selected bias voltage outputted by a selected voltage port and a selected bias voltage port, respectively. The power management circuit can be controlled to dynamically increase the selected bias voltage at the selected bias voltage port in case the selected bias voltage drops below a defined bias voltage threshold. As such, it may be possible to maintain the selected bias voltage at a desirable level, thus enabling the amplifier circuit(s) to operate with improved linearity and efficiency.

In one example, a circuit includes a first node to receive an analog signal that is an amplitude modulated radio-frequency signal for a digital signal. An output node is configured to provide an output signal indicative of rising and falling edges of an envelope of the analog signal. The rising and falling edges are indicative of rising and falling edges of the digital signal. A first current path is disposed between a power supply node and the first node. The first current path includes a first transistor coupled between the first node and a first bias source. The first bias source is coupled between the first transistor and the power supply node. The output node is coupled to a first intermediate node in the first current path between the transistor and the first bias source. A control terminal of the first transistor is coupled to the output node via a feedback network.