A power amplifier circuit includes a power amplifier, first and second filters, and first and second output paths. The power amplifier is able to amplify both of a first signal and a second signal. The frequency of the second signal is higher than that of the first signal. The first filter includes a first inductor and attenuates the second signal amplified in the power amplifier. The first inductor serves as a path for the first signal amplified in the power amplifier. The second filter includes a first capacitor and attenuates the first signal amplified in the power amplifier. The first capacitor serves as a path for the second signal amplified in the power amplifier. The first signal outputted from the first filter is supplied to the first output path. The second signal outputted from the second filter is supplied to the second output path.

An apparatus measures a speaker impedance. A DAC converts a known digital input signal to an audio frequency first analog voltage signal. Resistors with known resistance attenuate the first analog voltage signal to generate a current. The known resistance effectively determines the current because the known resistance is high relative to the speaker impedance. The current is sourced into the speaker to generate a second analog voltage signal. The known resistance is sufficiently high to cause the second analog voltage signal to be inaudible as transduced by the speaker. An amplifier amplifies the second analog voltage signal with a known gain to generate a third analog voltage signal. An ADC converts the third analog voltage signal to a digital output signal. A processing element calculates the impedance of the speaker proportional to the digital output signal based on the known digital input signal, the known resistance, and the known gain.

Methods, systems, and circuities for selectively connecting an RF signal to front end circuitry and selectively attenuating the RF signal are disclosed. In one example, an interface circuitry includes switching circuitry and attenuator circuitry. The switching circuitry is connected in series between an output of an amplifier and a front end circuitry configured to transmit a radio frequency (RF) signal output by the amplifier. The switching circuitry connects the output of the amplifier to a selected one or more front end circuitry inputs to create one or more signal paths. The attenuator circuitry is connected between the output of the amplifier and ground to create an attenuation path in a shunt configuration relative to the one or more signal paths. The attenuator circuitry is configured to attenuate the RF signal.

A multimode envelope tracking (ET) circuit and related apparatus is provided. The multimode ET circuit is configured to provide an ET voltage(s) to an amplifier circuit(s) for amplifying a radio frequency (RF) signal(s) that may correspond to a wider range of modulation bandwidth. In this regard, the multimode ET circuit is configured to switch dynamically and opportunistically between different operation modes based on the modulation bandwidth of the RF signal(s). In examples discussed herein, the multimode ET circuit is configured to support a single amplifier circuit in a high-modulation-bandwidth mode and an additional amplifier circuit(s) in a mid-modulation-bandwidth mode and a low-modulation-bandwidth mode. By switching dynamically and opportunistically between different operation modes, it may be possible to reduce undesired series resonance that may cause distortion in the ET voltage(s), thus helping to improve efficiency and performance of the amplifier circuit(s) supported by the multimode ET circuit.

A receiver front end (300) having low noise amplifiers (LNAs) is disclosed herein. A cascode having a “common source” configured input FET and a “common gate” configured output FET can be turned on or off using the gate of the output FET. A first switch (235) is provided that allows a connection to be either established or broken between the source terminal of the input FET of each LNA. A drain switch (260) is provided between the drain terminals of input FETs to place the input FETs in parallel. This increases the g.sub.m of the input stage of the amplifier, thus improving the noise figure of the amplifier.

Methods and apparatus for providing amplifier protection for a radio frequency (RF) front-end circuit. An example RF front-end circuit generally includes an amplifier with a gain, a first sensor configured to sense a first power (or voltage) of a first node coupled to an input of the amplifier, a second sensor configured to sense a second power (or voltage) of a second node coupled to an output of the amplifier, and logic coupled to the first and second sensors. The logic is generally configured to determine that the second power (or voltage) is outside a range based on the gain and the first power (or voltage) and to take an action to protect the amplifier based on the determination. By utilizing the techniques and apparatus described herein, protection can be provided to the amplifier(s) in an RF front-end circuit without significantly impacting the performance of the RF front-end circuit.

In an embodiment an integration circuit has a first input terminal configured to receive a first input signal, a second input terminal configured to receive a second input signal, an output terminal to provide an output signal as a function of the first and the second input signal, a first and a second amplifier, each being switchably connected between the first or the second input terminal and the output terminal, and a capacitor which is switchably coupled in a feedback loop either of the first or of the second amplifier such that the capacitor and one of the first and the second amplifier form an inverting integrator providing the output signal. Therein the integration circuit is prepared to be operated in a first and a second subphase, wherein in each of first and second subphases one of the first and the second input signals is supplied to the inverting integrator and the respective other one of first and the second input signals is supplied to the respective other one of the first and the second amplifier.

An apparatus measures a speaker impedance. A DAC converts a known digital input signal to an audio frequency first analog voltage signal. Resistors with known resistance attenuate the first analog voltage signal to generate a current. The known resistance effectively determines the current because the known resistance is high relative to the speaker impedance. The current is sourced into the speaker to generate a second analog voltage signal. The known resistance is sufficiently high to cause the second analog voltage signal to be inaudible as transduced by the speaker. An amplifier amplifies the second analog voltage signal with a known gain to generate a third analog voltage signal. An ADC converts the third analog voltage signal to a digital output signal. A processing element calculates the impedance of the speaker proportional to the digital output signal based on the known digital input signal, the known resistance, and the known gain.

A power amplifier module that includes a power amplifier having a plurality of amplifier gain stages, a memory device including a plurality of memory locations, and a controller to receive a control signal having at least one of a first state and a second state. The plurality of memory locations includes at least one first memory location to store a first set of configuration parameters for operation in a first mode, and at least one second memory location to store a second set of configuration parameters for operation in a second mode. The controller configures the power amplifier module in the first mode based on the first set of configuration parameters responsive to receiving the control signal having the first state and configures the power amplifier module in the second mode based on the second set of configuration parameters responsive to receiving the control signal having the second state.

A chopper-stabilized amplifier includes a first transconductance amplifier and a first chopper circuit coupled to an input of the first transconductance amplifier. A second chopper circuit is coupled to an output of the first transconductance amplifier. The chopper-stabilized amplifier also includes second and third transconductance amplifiers having inputs coupled to the output of the first transconductance amplifier. The second transconductance amplifier produces an output responsive to a first notch clock signal having a first phase relative to the chopping of the second chopper circuit. The third transconductance amplifier produces an output responsive to a second notch clock signal having a second phase relative to the first phase. The output signals produced by the second and third transconductance amplifiers are added to filter ripple noise at the outputs of the second and third transconductance amplifiers.