A power amplifier circuit includes first and second bias circuits configured to provide first and second biases, respectively, a first transistor having an emitter connected to a reference potential, a base configured to receive the first bias via a first resistor and receive a radio-frequency input signal via a first capacitor, and a collector configured to output an amplified radio-frequency signal, a second transistor having a base connected to the reference potential via a second capacitor and configured to receive the second bias via a second resistor, an emitter configured to receive the radio-frequency signal, and a collector connected to a power supply potential via a third inductor and configured to output a radio-frequency output signal, and an impedance circuit having a first end connected to an output section of the second bias circuit and configured to apply an alternating-current signal to a path extending from the second bias circuit.

An analog front-end (AFE) circuit for conditioning a sensor signal is disclosed. The AFE circuit includes a first stage configured to amplify and filter the sensor signal. The first stage comprises a biquadratic filter comprising a first plurality of DC-coupled transconductance amplifiers. The AFE further includes a second stage configured to further amplify and filter the amplified sensor signal, and to compensate a direct current (DC) offset of the first stage. The second stage comprises a second plurality of AC-coupled transconductance amplifiers. Each transconductance amplifier of the first plurality and of the second plurality has a programmable transconductance and comprises a plurality of subthreshold-biased transistors.

A power amplifier circuit includes a first transistor having a first terminal to which a voltage corresponding to a variable power supply voltage is to be supplied and a second terminal to which a radio-frequency signal is to be supplied, the first transistor being configured to amplify the radio-frequency signal, a bias circuit configured to supply a bias current or voltage to the second terminal of the first transistor, and an adjustment circuit configured to adjust the bias current or voltage in accordance with the variable power supply voltage supplied from a power supply terminal.

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.

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.

Disclosed are methods for biasing amplifiers and for manufacturing bias circuits bias for biasing amplifiers. A power amplifier bias circuit can include an emitter follower device and an emitter follower mirror device coupled to form a mirror configuration. The emitter follower device can be configured to provide a bias signal for a power amplifier at an output port. The power amplifier bias circuit can include a reference device configured to mirror an amplifying transistor of an amplifying device of the power amplifier. The emitter follower mirror device can be configured to provide a mirror bias signal to the reference device. A node between the emitter follower device and the emitter follower mirror device can have a voltage of approximately twice a base-emitter voltage (2Vbe) of the amplifying transistor.

Disclosed are methods for biasing amplifiers and for manufacturing bias circuits bias for biasing amplifiers. A power amplifier bias circuit can include an emitter follower device and an emitter follower mirror device coupled to form a mirror configuration. The emitter follower device can be configured to provide a bias signal for a power amplifier at an output port. The power amplifier bias circuit can include a reference device configured to mirror an amplifying transistor of an amplifying device of the power amplifier. The emitter follower mirror device can be configured to provide a mirror bias signal to the reference device. A node between the emitter follower device and the emitter follower mirror device can have a voltage of approximately twice a base-emitter voltage (2Vbe) of the amplifying transistor.

Systems and methods related to power amplification and power supply control. A method of operating a power amplification control system can include receiving, by an interface, a transceiver control signal from a transceiver. The method can further include generating, by a power amplifier control component, a power amplifier control signal based on the transceiver control signal from the transceiver. The method can also include generating, by a power supply control component, a power supply control signal based on one or more of the transceiver control signal from the transceiver or a local control signal from the power amplifier control component.

Systems and methods related to power amplification and power supply control. A method of operating a power amplification control system can include receiving, by an interface, a transceiver control signal from a transceiver. The method can further include generating, by a power amplifier control component, a power amplifier control signal based on the transceiver control signal from the transceiver. The method can also include generating, by a power supply control component, a power supply control signal based on one or more of the transceiver control signal from the transceiver or a local control signal from the power amplifier control component.

An RF amplifier for implementation in SiGe HBT technology is described. The RF amplifier has a cascode stage comprising a common base (CB) transistor and a common emitter (CE) transistor arranged in series between a first voltage rail and a second voltage rail. An RF input is coupled to the base of the CE transistor and an RF output is coupled to the collector of the CB transistor. The RF amplifier includes a CB power-down circuit arranged between the base of the CB transistor and the second voltage rail and a CE power-down circuit arranged between the base of the CE transistor and the second voltage rail. In a power-down mode the CE power-down circuit couples the base of the common-emitter-transistor to the second voltage rail. The CB power-down mode circuit couples the base of the CB transistor to the second voltage rail via a high-ohmic path.