pHEMT-based circuits and methods of improving the linearity thereof. One example pHEMT circuit includes a pHEMT connected between an input terminal and a load and a non-linear resistance connected to the pHEMT. The pHEMT produces a first harmonic signal at the load responsive to being driven by an input signal of a fundamental frequency received at the input terminal, the first harmonic signal having a first phase. The non-linear resistance has a resistance selected to produce a second harmonic signal at the load having a second phase opposite to the first phase. Methods can include determining a first amplitude and a first phase of a first harmonic signal produced at the load by a pHEMT in an ON state, and tuning the non-linear resistance to produce at the load a second harmonic signal having a second amplitude and a second phase that minimizes a net harmonic signal at the load.

The disclosure relates to an alternating current (AC) coupling circuit including first and second capacitors having first and second input terminals configured to receive an input differential signal and generate an output differential signal at first and second output terminals of the first and second capacitors. The AC coupling circuit further includes a baseline wander correction circuit configured to make the output differential signal resistant to baseline wander due to the input differential signal including one or more time intervals of unbalanced data. The baseline wander correction circuit includes a differential difference amplifier (DDA) having a first differential input configured to receive the input differential signal, a differential output configured to generate a compensation differential signal, and a second differential input configured to receive the compensation differential signal. The compensation differential signal is applied to the output terminals of the first and second capacitors via a pair of resistors, respectively.

In one implementation, a circuit can include a reference pin and an operational amplifier that can include an output pin, an inverting input pin and a non-inverting input pin. The inverting input pin can be electrically coupled to the output pin via a first impedance and to the reference pin via a second impedance. The non-inverting input pin can be electrically coupled to the reference pin via a third impedance and can be configured to receive a detection signal. The reference pin can be configured to receive a detection reference signal associated with the detection signal.

This application relates to circuitry for monitoring for instability of an amplifier. The amplifier (100) has a first signal path between an amplifier input (IN.sub.N) and an amplifier output (V.sub.OUT) and a feedback path from the output to form a feedback loop with at least part of the first signal path. A comparator (212) has a first input configured to receive a first signal (IN.sub.N) derived from a first amplifier node which is part of said feedback loop and a second input configured to receive a second signal (IN.sub.P) derived from a second amplifier node which varies with the signal at the amplifier input but does not form part of said feedback loop. The comparator is configured to compare the first signal to the second signal and generate a comparison signal (COMP), wherein in the event of amplifier instability the comparison signal comprises a characteristic indicative of amplifier instability.

The semiconductor device includes a Hall element, a first differential pair, a second differential pair, an output amplifier circuit, and a voltage divider circuit. The Hall element outputs a signal that is dependent on stress to be applied to a semiconductor substrate to the first differential pair. The voltage divider circuit divides a voltage into a divided voltage having a voltage dividing ratio that is dependent on the stress. The first differential pair outputs a first current based on the signal. The second differential pair outputs a second current based on the divided voltage and a reference voltage. The output amplifier circuit outputs a voltage based on the first and second currents. A gain of the output amplifier circuit is approximated by a sum of a difference between stress dependence coefficients of transconductances of the first and second differential pairs and a stress dependence coefficient of the voltage dividing ratio.

This application relates to circuitry for monitoring for instability of an amplifier. The amplifier (100) has a first signal path between an amplifier input (IN.sub.N) and an amplifier output (V.sub.OUT) and a feedback path from the output to form a feedback loop with at least part of the first signal path. A comparator (212) has a first input configured to receive a first signal (IN.sub.N) derived from a first amplifier node which is part of said feedback loop and a second input configured to receive a second signal (IN.sub.P) derived from a second amplifier node which varies with the signal at the amplifier input but does not form part of said feedback loop. The comparator is configured to compare the first signal to the second signal and generate a comparison signal (COMP), wherein in the event of amplifier instability the comparison signal comprises a characteristic indicative of amplifier instability.

Examples of the disclosure include an amplifier system comprising an amplifier having an input to receive an input signal, and an output to provide an amplified output signal, the amplifier having a power level indicative of at least one of the input signal power and the amplified output signal power, and a linearizer coupled to the amplifier and having a plurality of modes of operation including a fully disabled mode and a fully enabled mode, the linearizer being configured to determine the power level of the amplifier, select a mode of operation of the plurality of modes of operation based on the power level of the amplifier, determine one or more linearization parameters corresponding to the selected mode of operation, and control linearization of the amplified output signal based on the determined one or more linearization parameters.

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.

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.

Examples of the disclosure include an amplifier system comprising an amplifier having an input to receive an input signal, and an output to provide an amplified output signal, the amplifier having a power level indicative of at least one of the input signal power and the amplified output signal power, and a linearizer coupled to the amplifier and having a plurality of modes of operation including a fully disabled mode and a fully enabled mode, the linearizer being configured to determine the power level of the amplifier, select a mode of operation of the plurality of modes of operation based on the power level of the amplifier, determine one or more linearization parameters corresponding to the selected mode of operation, and control linearization of the amplified output signal based on the determined one or more linearization parameters.