A multi-stage amplifier with a high signal-to-noise ratio is introduced. Multiple amplification stages are cascaded between an input terminal and an output terminal of the amplifier. A controller switches the output stage among the multiple amplification stages from a normal mode to an attenuation mode in response to the amplifier input being lower than the threshold. In the attenuation mode, the output stage provides an attenuation resistor coupled in series with the load resistor of the amplifier. Noise is successfully attenuated by the attenuation-mode output stage.

An amplifier circuit has an amplification path including an amplifier and a bypass path configured to bypass at least the amplifier. The bypass path includes a switch coupled in series on the bypass path and another switch coupled in series between the bypass path and ground. The amplification path further includes an inductor coupled on an output side with respect to the amplifier and a switch coupled between the inductor and ground on a path between the inductor and the amplifier.

A splitter circuit includes: a signal divider configured to split and transmit a first radio frequency (RF) signal received in a first receiving mode in which a first communication scheme and a second communication scheme are simultaneously performed; a first bypass circuit configured to bypass the signal divider to transmit a second RF signal received in a second receiving mode in which the first communication scheme is performed; and a second bypass circuit configured to bypass the signal divider to transmit a third RF signal received in a third receiving mode in which the second communication scheme is performed.

A front end module (FEM) for a 5.6/6.6 GHz Wi-Fi acoustic wave resonator RF filter circuit. The device can include a power amplifier (PA), a 5.6/6.6 GHz resonator, and a diversity switch. The device can further include a low noise amplifier (LNA). The PA is electrically coupled to an input node and can be configured to a DC power detector or an RF power detector. The resonator can be configured between the PA and the diversity switch, or between the diversity switch and an antenna. The LNA may be configured to the diversity switch or be electrically isolated from the switch. Another 5.6/6.6 GHZ resonator may be configured between the diversity switch and the LNA. In a specific example, this device integrates a 5.6/6.6 GHz PA, a 5.6/6.6 GHZ bulk acoustic wave (BAW) RF filter, a single pole two throw (SP2T) switch, and a bypassable LNA into a single device.

A splitter circuit includes: a signal divider configured to split and transmit a first radio frequency (RF) signal received in a first receiving mode in which a first communication scheme and a second communication scheme are simultaneously performed; a first bypass circuit configured to bypass the signal divider to transmit a second RF signal received in a second receiving mode in which the first communication scheme is performed; and a second bypass circuit configured to bypass the signal divider to transmit a third RF signal received in a third receiving mode in which the second communication scheme is performed.

An LNA having a plurality of paths, each of which can be controlled independently to achieve a gain mode. Each path includes at least an input FET and an output FET coupled in series. A gate of the output FET is controlled to set the gain of the LNA. Signals to be amplified are applied to the gate of the input FET. Additional stacked FETs are provided in series between the input FET and the output FET.

An LNA circuit includes: paths provided between an input and an output terminals, an LNA provided in at least one path, and a selector selecting one path. The LNA includes: a MOS transistor coupled between a first and a second power supplies, a first inductor coupled to a source of the MOS transistor, a capacitor formed between a gate and the source of the MOS transistor, a second inductor coupled between the gate of the MOS transistor and the input terminal, and a changeover switch coupled parallelly with at least one of the capacitor, and the first and the second inductors. The selector switches between a first state that one path is selected and the changeover switch is on, and a second state that another path is selected and the changeover switch is off. Alternatively, the one path and the another path are respectively provided without and with the LNA.

A front end module (FEM) for a 5.5 GHz Wi-Fi acoustic wave resonator RF filter circuit. The device can include a power amplifier (PA), a 5.5 GHz resonator, and a diversity switch. The device can further include a low noise amplifier (LNA). The PA is electrically coupled to an input node and can be configured to a DC power detector or an RF power detector. The resonator can be configured between the PA and the diversity switch, or between the diversity switch and an antenna. The LNA may be configured to the diversity switch or be electrically isolated from the switch. Another 5.5 GHZ resonator may be configured between the diversity switch and the LNA. In a specific example, this device integrates a 5.5 GHz PA, a 5.5 GHZ bulk acoustic wave (BAW) RF filter, a single pole two throw (SP2T) switch, and a bypassable LNA into a single device.

A headset communication system with improved functionality. The headset communication system may include hear-through limiter functionality. The headset communication system may include failsafe functionality. The headset communication system may include multichannel, mixing, passive push-to-talk functionality. The headset communication system may include near field magnetic induction functionality.

A clamping circuit that may be used to provide efficient and effective voltage clamping in an RF front end. The clamping circuit comprises two series coupled signal path switches and a bypass switch coupled in parallel with the series coupled signal path switches. A diode is coupled from a point between the series coupled signal path switches to a reference potential. In addition, an output selection switch within an RF front end has integrated voltage clamping to more effectively clamp the output voltage from the RF front end. Additional output clamping circuits can be used at various places along a direct gain signal path, along an attenuated gain path and along a bypass path.