One or more example relate, generally, to generating radio frequency (RF) signals. An apparatus may include a signal generator, an amplification stage, and a feedback control loop. The signal generator may generate a pulsed radio frequency (RF) signal at least partially responsive to a digital pulsed waveform defined by one or more commands. The amplification stage may amplify the pulsed RF signal. The feedback control loop may be coupled to the amplification stage to regulate a power level of respective steps of the pulsed RF signal.

A bidirectional RF circuit, preferably including a plurality of terminals, a switch, a transistor, a coupler, and a feedback network. The circuit can optionally include a drain matching network, an input matching network, and/or one or more tuning inputs. In some variations, the circuit can optionally include one or more impedance networks, such as an impedance network used in place of the feedback network; in some such variations, the circuit may not include a coupler, switch, and/or input matching network. A method for circuit operation, preferably including operating in an amplifier mode, operating in a rectifier mode, and/or transitioning between operation modes.

A technology related to a power amplifier used in a wireless communication circuit is disclosed. A radio frequency (RF) power amplifier includes a plurality of unit differential amplifiers of which inputs are connected to a common input terminal and outputs are connected to a common adder, and having a gain of a weight of a corresponding bit of a binary gain control word. Each of the differential amplifiers may be configured as a complementary metal-oxide semiconductor (CMOS) differential cascode amplifier. In addition, the RF power amplifier may include a structure in which a plurality of attenuators of the same structure are cascade-connected so that an attenuation rate may be linearly and digitally controlled and an output of each attenuator is connected to an output adder through differential buffers of which turn-on and turn-off are controlled by a controller.

Embodiments relate generally to hearing protection devices which incorporate a calibration mode which allows the user to perform a calibration test to determine an individualized hearing threshold. Embodiments of the device may also comprise a normal mode to prevent input signals greater than the individualized hearing threshold from being transmitted to the user's ear canal. In addition, embodiments may comprise a normal mode configured to limit input signals to less than or equal to a standard industry threshold in the case no calibration test has been completed by the user. This may increase user comfort and prevent hearing damage.

An exemplary structure has an output stage; a driver stage; and a power stage connected between the driver stage and the output stage. The power stage includes a first transistor and a second transistor connected in series between the driver stage and the output stage. The power stage also includes a third transistor and a fourth transistor connected in series between the driver stage and the output stage. An inductor has a first terminal electrically connected to a first node between the first transistor and the second transistor and a second terminal electrically connected to a second node between the third transistor and the fourth transistor. The inductor is configured to provide impedance matching between common-gate stages of the power stage.

A program gain amplifier includes an operational amplifier and a capacitor array. The capacitor array includes a first, second, and third capacitors selectively coupled to the operational amplifier or ground according to a first, second, and third switches, respectively. The first, second, and third capacitors have a first, second, and third capacitance, respectively. The third capacitance equals a sum of the first and second capacitance. In a first configuration, the first and second switches are operated at a first conductive state, and the third switch is operated at a second conductive state. When converting to a second configuration from the first configuration, the third switch is operated at the first conductive state, and the first and second switches are operated at the second conductive state. The gain being provided to an input signal in the first and second configurations are the same.

Equalizer circuitry includes a differential target voltage input, an equalizer output, a first operational amplifier, and a second operational amplifier. The differential target voltage input includes a target voltage input node and an inverted target voltage input node. The first operational amplifier and the second operational amplifier are coupled in series between the differential target voltage input and the equalizer output. The first operational amplifier is configured to receive a target voltage signal and provide an intermediate signal based on the target voltage input signal. The second operational amplifier is configured to receive the intermediate signal and an inverted target voltage signal and provide an output signal to the equalizer output. The first operational amplifier and the second operational amplifier are interconnected with one or more passive components such that a transfer function between the differential target voltage input and the equalizer output is a second-order complex-zero function.

An example method of operation may include initiating an automated tuning procedure, detecting via one or more microphones a sound measurement associated with an output of one or more speakers at two or more locations, determining a number of speech transmission index (STI) values equal to a number of microphones, and averaging the speech transmission index values to identify a single speech transmission index value.

A feedforward echo cancellation device includes: a first impedance circuit for responding to a transmission current to output a first current to a node; an echo cancellation current generating circuit for drawing an echo cancellation current from the node; a circuit module that is coupled to the echo cancellation current generating circuit and the node has a first impedance value adjusted based on a system convergence index of a communication device, where the first impedance value is used to determine a gain of a programmable gain amplifier in the communication device; and a second impedance circuit for responding to the transmission current to output a second current to the node, where a second impedance value of the second impedance circuit is adjusted based on the first impedance value of the circuit module accordingly. Specifically, the node is coupled to an input terminal of the programmable gain amplifier.

Systems and methods that integrate a directional coupling function with directivity that does not have output loss are disclosed. For example, a power amplifier circuit arrangement includes an input terminal to receive an input signal; amplifier circuitry including a first amplifier stage, a second amplifier stage, and a virtual ground node, where an input of the first amplifier stage is coupled to the input terminal, an output of the first amplifier stage is coupled to an input of the second amplifier stage via the virtual ground node, and an output of the second amplifier stage is coupled to the input of the first amplifier stage via feedback circuitry; an output terminal coupled to the output of the second amplifier stage, the output terminal to output an amplified signal; and a directional coupler terminal coupled to the virtual ground node.