An amplifier circuit and a method of recovering an input signal in the amplifier circuit are provided. The amplifier circuit may recover an input signal by using a time constant and an output signal of a signal amplifier which is delayed by a certain period, based on characteristics of an inverse Laplace transform of a transfer function of the signal amplifier. A time required for recovering the input signal may be shorter than the time constant of the signal amplifier.

Apparatus and methods for power detection with enhanced dynamic range are provided. In certain embodiments, a front end system includes a power amplifier that amplifies a radio frequency (RF) input signal to generate an RF output signal, a directional coupler that generates a sensed RF signal based on sensing the RF output signal from the power amplifier, and a power detector that processes the sensed RF signal to generate a detection signal indicating an output power of the power amplifier. Additionally, the power detector includes two or more detection paths providing different amounts of gain to the sensed RF signal from the directional coupler.

A Programmable-Gain Amplifier (PGA) has programming steps that are linear when expressed in Decibels (linear-in-dB). A Recursive Current Division (RCD) resistor network generates currents that are selected by programmable switches to connect to a summing node input of an amplifier. A feedback resistor is connected across the summing node and the amplifier output. The resistor network has only three resistance values regardless of the number of currents selectable as programming steps. The value of a third resistor is set equal to the equivalent resistance of a second resistor in parallel with a series connection of a first resistor and the third resistors. Each final cell in the resistor network is equivalent to the third resistor, allowing recursive division of adjacent currents. The ratio of adjacent currents remains constant for all cells. Recursive Current Division (RCD) produces linear-in-dB programming steps. Floating switches are avoided since switches connect to ground.

An amplifier circuit includes an amplifier having an amplifier input and an amplifier output. A transformer disposed to provide a signal for driving a load includes a primary winding in series with the amplifier output. A secondary winding of the transformer is coupled to the amplifier input where the primary winding and the secondary winding are arranged such that a portion of a magnetic field generated by the primary winding couples to the secondary winding so as to establish a magnetically coupled feedback loop from the amplifier output to the amplifier input. A loop gain of the magnetically coupled feedback loop is substantially independent of an impedance of the load and is defined at least in part by a coupling factor and turn-ratio of the transformer. The load may be included within an output load arrangement including a balun.

An amplifier circuit includes an amplifier having an amplifier input and an amplifier output. The amplifier circuit includes a transformer having a primary winding in series with the amplifier output and a secondary winding coupled to the amplifier input. The primary winding and the secondary winding are arranged such that a portion of a magnetic field generated by the primary winding couples to the secondary winding through a magnetically coupled feedback loop, thereby providing feedback from the amplifier output to the amplifier input. An output load arrangement is connected to the primary winding wherein the output arrangement includes a balun. The amplifier circuit may be implemented as an integrated circuit and where the primary and secondary windings are integrated in different metal layers of the integrated circuit or are otherwise arranged to effect a desired degree of magnetic coupling and feedback from the amplifier output to the amplifier input.

The present disclosure relates to an amplifier circuit (2) for a capacitive transducer (1), comprising a preamplifier (8) adapted to receive a transducer signal through an input node (9) and to provide an amplified signal at an output node (10), and a transconductance amplifier (11) comprising a first input (12) and an output (14), wherein the first input (12) of the transconductance amplifier (11) is connected to the output node (10), and the output (14) of the transconductance amplifier (11) is connected to the input node (9).

An amplifier circuit including a first amplifier having a first amplifier input and a first amplifier output and a transformer including a first transformer component having a first primary winding in series with the first amplifier output and a first secondary winding coupled to the first amplifier input. The first primary winding and the first secondary winding are arranged such that a portion of a first magnetic field generated by the first primary winding couples to the first secondary winding through a first magnetically coupled feedback loop. The transformer further includes a second transformer component having a second primary winding in series with an output of a second amplifier and a second secondary winding coupled to an input of the second amplifier input. A portion of a second magnetic field generated by the second primary winding couples to the second secondary winding through a second magnetically coupled feedback loop.

An amplifier circuit including a first amplifier having a first amplifier input and a first amplifier output and a transformer including a first transformer component having a first primary winding in series with the first amplifier output and a first secondary winding coupled to the first amplifier input. The first primary winding and the first secondary winding are arranged such that a portion of a first magnetic field generated by the first primary winding couples to the first secondary winding through a first magnetically coupled feedback loop. The transformer further includes a second transformer component having a second primary winding in series with an output of a second amplifier and a second secondary winding coupled to an input of the second amplifier input. A portion of a second magnetic field generated by the second primary winding couples to the second secondary winding through a second magnetically coupled feedback loop.

In an embodiment, a method includes connecting a first subset of a set of stages of a power amplifier to a supply voltage, connecting a second subset of the set of stages to a reference voltage different than the supply voltage, switching a third subset of the set of stages according to a switching frequency, assigning numbers of stages in the first subset, the second subset, and the third subset based on a power requirement of the power amplifier, and amplifying a transmit signal using the first subset, the second subset, and the third subset to generate an amplified transmit signal.

An amplifier circuit may include a first gain stage configured to receive an input signal at the first gain stage input and apply a first gain to the input signal to generate a first gain stage output signal at the first gain stage output, a second gain stage configured to receive the first gain stage output signal at the second gain stage input and apply a second gain to the first gain stage output signal to generate a second gain stage output signal at the second gain stage output, a feedforward gain stage configured to receive the input signal at the feedforward gain stage input and apply a feedforward gain to the input signal to generate a feedforward gain stage output signal at the feedforward gain stage output, and a compensation network coupled between the first gain stage output and the feedforward gain stage output.