Amplifiers, amplification circuits, and phase shifters, for example, for flexibly adjusting an output phase to thereby meet a requirement of a constant phase on a link in a communications field, are provided. In one aspect, an amplifier includes first, second, and third MOS transistors. The first MOS transistor includes a gate separately coupled to a signal input end and a bias voltage input end, a source coupled to a power supply, and a drain separately coupled to sources of the second and third MOS transistors. A drain of the third MOS transistor is coupled to a ground, and a drain of the second MOS transistor is coupled to a signal output end. The bias voltage input end is configured to receive a bias voltage to adjust a phase difference between an input signal at the signal input end and an output signal at the signal output end.

An apparatus includes a transformer including a first inductor, a second inductor, and a third inductor. The apparatus also includes a power amplifier having an output coupled to the first inductor, a low-noise amplifier having an input coupled to a first terminal of the third inductor, and a fourth inductor having a first terminal and a second terminal, wherein the second terminal of the fourth inductor is coupled to a second terminal of the third inductor. The apparatus also includes a switch coupled between the first terminal of the third inductor and the first terminal of the fourth inductor.

Disclosed herein are signal amplifiers having a plurality of amplifier cores. Individual amplifier cores can be designed to enhance particular advantages while reducing other disadvantages. The signal amplifier can then switch between amplifier cores in a particular gain mode to achieve desired performance characteristics (e.g., improving noise figure or linearity). Examples of signal amplifiers disclosed herein include amplifier architectures with a low noise figure amplifier core that reduces the noise figure and a linearity boost amplifier core that increases linearity. The disclosed signal amplifiers can switch between a first active core and a second active core for a single or particular gain mode to achieve desired signal characteristics during different time periods.

Disclosed herein are signal amplifiers having a plurality of amplifier cores. Individual amplifier cores can be designed to enhance particular advantages while reducing other disadvantages. The signal amplifier can then switch between amplifier cores in a particular gain mode to achieve desired performance characteristics (e.g., improving noise figure or linearity). Examples of signal amplifiers disclosed herein include amplifier architectures with a low noise figure amplifier core that reduces the noise figure and a linearity boost amplifier core that increases linearity. The disclosed signal amplifiers can switch between a first active core and a second active core for a single or particular gain mode to achieve desired signal characteristics during different time periods.

A modulated RF carrier produced at the output of the polar transmitter's switch-mode power amplifier (SMPA) is conveyed to an output filter network comprising a harmonic low-pass filter (LPF) connected in parallel with an absorptive high-pass filter (HPF). Together the harmonic LPF and absorptive HPF pass the fundamental component of the modulated RF carrier to the polar transmitter's load while also absorbing higher harmonic components that would otherwise be undesirably reflected back toward the output of the SMPA.

According to at least one example of the disclosure, a power amplifier is provided comprising a first power switch of a first type being configured to receive an input signal and provide an amplified output signal to an output connection configured to be coupled to a load, and a second power switch of a second type different than the first type, the second power switch being configured to improve a linearity of the power amplifier and being coupled to the output connection.

Circuits and methods for a multi-gain mode amplifier, particularly an LNA, that achieves wideband output impedance matching and high gain while maintaining low power and a low NF in a highest gain mode, and which can switch to one or more lower gain modes that achieve higher linearity with lower power. In a highest gain mode, an inductor is selectively inserted between the amplified-signal terminal of an amplification core and an output LC output matching network. The inductor, when inserted, provides wideband output impedance matching, functioning as a series peaking inductor; accordingly, the inserted inductor delays current flow to the output capacitor and lowers the rise time of signal changes across the output capacitor. In addition, higher gain can be achieved compared to a conventional LC output impedance matching topology due to a higher impedance at the amplified-signal terminal of the amplification core.

Circuits and methods for a multi-gain mode amplifier, particularly an LNA, that achieves wideband output impedance matching and high gain while maintaining low power and a low NF in a highest gain mode, and which can switch to one or more lower gain modes that achieve higher linearity with lower power. In a highest gain mode, an inductor is selectively inserted between the amplified-signal terminal of an amplification core and an output LC output matching network. The inductor, when inserted, provides wideband output impedance matching, functioning as a series peaking inductor; accordingly, the inserted inductor delays current flow to the output capacitor and lowers the rise time of signal changes across the output capacitor. In addition, higher gain can be achieved compared to a conventional LC output impedance matching topology due to a higher impedance at the amplified-signal terminal of the amplification core.

An apparatus for detecting difference in operating characteristics of a main circuit by using a replica circuit is presented. In one exemplary case, a sensed difference in operating characteristics of the two circuits is used to drive a tuning control loop to minimize the sensed difference. In another exemplary case, several replica circuits of the main circuit are used, where each is isolated from one or more operating variables that affect the operating characteristic of the main circuit. Each replica circuit can be used for sensing a different operating characteristic, or, two replica circuits can be combined to sense a same operating characteristic.

An apparatus for detecting difference in operating characteristics of a main circuit by using a replica circuit is presented. In one exemplary case, a sensed difference in operating characteristics of the two circuits is used to drive a tuning control loop to minimize the sensed difference. In another exemplary case, several replica circuits of the main circuit are used, where each is isolated from one or more operating variables that affect the operating characteristic of the main circuit. Each replica circuit can be used for sensing a different operating characteristic, or, two replica circuits can be combined to sense a same operating characteristic.