A radio frequency circuit includes a power amplifier configured to selectively amplify one of a first radio frequency signal and a second radio frequency signal that have different bandwidths, and when the first radio frequency signal is input to the power amplifier, a first bias signal is applied to the power amplifier, and when the second radio frequency signal is input to the power amplifier, a second bias signal different from the first bias signal is applied to the power amplifier.

A radio frequency circuit includes a transmit power amplifier, a differential transmit signal path having first and second paths, and first and second baluns. The first balun can be configured to convert a single ended transmit signal into a differential transmit signal, and the second balun can be configured to convert the differential transmit signal back to a single ended transmit signal. The circuit can also include a pair of transmit filters between the first and second baluns and including a first transmit filter connected in the first path and a second transmit filter connected in the second path. The second balun cancels harmonic noise generated by the pair of transmit filters.

An amplifier circuit comprising a power amplifier and a protection circuit coupled to the power amplifier. The protection circuit is configured to detect an overdrive condition and, in response to detecting an overdrive condition, apply a clamping status to the protection circuit to reduce a bias current to the power amplifier. The protection circuit has a capacitor and a recovery circuit including: a sensing component configured to monitor a change of charging and discharging currents to and from the capacitor respectively during the clamping status; a first device configured to set a time constant of the recovery circuit; and a second device configured to reset the protection circuit to remove the clamping status when the change of charging or discharging current is beyond a predetermined threshold.

A micro electro-mechanical film speaker device is provided. A signal input terminal of a signal amplifier circuit is connected to an external input circuit. A second output terminal of the signal amplifier circuit is connected to a negative terminal of a micro electro-mechanical film speaker. A first terminal of a first high-pass filter is connected to a first output terminal of the signal amplifier circuit. A second terminal of the first high-pass filter is connected to a positive terminal of the micro electro-mechanical film speaker. A first terminal of a second high-pass filter is connected to a feedback terminal of the signal amplifier circuit. A second terminal of the second high-pass filter is connected to the positive terminal of the micro electro-mechanical film speaker.

Apparatus and methods remove a voltage offset from an electrical signal, specifically a biomedical signal. A signal is received at a first operational amplifier and is amplified by a gain. An amplitude of the signal is monitored, by a first pair of diode stages coupled to an output of the first operational amplifier, for the voltage offset. The amplitude of the signal is then attenuated by the first pair of diode stages and a plurality of timing banks. The attenuating includes limiting charging, by the first pair of diode stages, of the plurality of timing banks and setting a time constant based on the charging. The attenuating removes the voltage offset persisting at a threshold for a duration of at least the time constant. Saturation of the signal is limited to a saturation recovery time while the saturated signal is gradually pulled into monitoring range over the saturation recovery time.

A thermally-isolated-metal-oxide-semiconducting (TMOS) sensor has inputs coupled to first and second nodes to receive first and second bias currents, and an output coupled to a third node. A tail has a first conduction terminal coupled to the third node and a second conduction terminal coupled to a reference voltage. A control circuit applies a control signal to a control terminal of the tail transistor based upon voltages at the first and second nodes so that a common mode voltage at the first and second nodes is equal to a reference common mode voltage. A differential current integrator has a first input terminal coupled to the second node and a second input terminal coupled to the first node, and provides an output voltage indicative of an integral of a difference between a first output current at the first input terminal and a second output current at the second input terminal.

The present invention discloses a CO alarm for a battery type generator, comprising a MCU control unit U2, configured to analyze and process signals, which is in a deep sleep state when the generator is not running, and enters a sleep plus timing wake-up working state after the engine is running; a CO sensor detection unit U3 connected to the MCU control unit, configured to convert the CO concentration in the environment into a corresponding electrical signal and output to the MCU control unit U2 for processing; an alarm indication unit U4 connected to the MCU control unit, configured to give an alarm prompt for the CO concentration and an alarm failure prompt.

In certain aspects, a method is provided for measuring power using a resistive element coupled between a power amplifier and an antenna. The method includes squaring a voltage from a first terminal of the resistive element to obtain a first signal, squaring a voltage from a second terminal of the resistive element to obtain a second signal, and generating a measurement signal based on a difference between the first signal and the second signal. In some implementations, the resistive element is implemented with a power switch.

To provide a lightweight and robust voltage amplifier and current amplifier for a test device for testing an electrical component, an amplifier is designed to output a test signal at a signal output between a positive output terminal and a negative output terminal. The amplifier includes a first half bridge and a second half bridge. A switching unit is provided, which is designed to connect the first half bridge and the second half bridge in parallel to the signal output in a first operating mode and to connect the first half bridge and the second half bridge in series with the signal output in a second operating mode.

A system is disclosed which allows for canceling high frequency rail to rail common mode swing at pulse-width modulation (PWM) frequency for a Class-D, H and G audio amplifier or a Linear Resonance Actuator (LRA) driver. This allows wide bandwidth current sensing without the need of external components, or large on-chip resistor-capacitor (RC) networks, facilitating integration of the sense resistor. In addition, the sense amplifier DC input common mode and audio band common mode swing is reduced, allowing a sense resistor high frequency common mode swing of a least twice the MOSFET gate break down voltages.