A regenerative current detection circuit includes a first power MOS transistor that is configured as a current mirror to a second power MOS transistor connected to drive a motor winding, a first feedback amplifier that compares a first regenerative current that flows in the first power MOS transistor with a second regenerative current that flows in the second power MOS transistor and outputs a comparison result, the first regenerative current being obtained by multiplying the second regenerative current by a current mirror ratio, and a current detection circuit that outputs a detection current based on the comparison result.

Temperature compensation circuits and methods for adjusting one or more circuit parameters of a power amplifier (PA) to maintain approximately constant Gain versus time during pulsed operation sufficient to substantially offset self-heating of the PA. Some embodiments compensate for PA Gain droop due to self-heating using a Sample and Hold (S&H) circuit. The S&H circuit samples and holds an initial temperature of the PA at commencement of a pulse. Thereafter, the S&H circuit generates a continuous measurement that corresponds to the temperature of the PA during the remainder of the pulse. A Gain Control signal is generated that is a function of the difference between the initial temperature and the operating temperature of the PA as the PA self-heats for the duration of the pulse. The Gain Control signal is applied to one or more adjustable or tunable circuits within a PA to offset the Gain droop of the PA.

Temperature compensation circuits and methods for adjusting one or more circuit parameters of a power amplifier (PA) to maintain approximately constant Gain versus time during pulsed operation sufficient to substantially offset self-heating of the PA. Some embodiments compensate for PA Gain droop due to self-heating using a Sample and Hold (S&H) circuit. The S&H circuit samples and holds an initial temperature of the PA at commencement of a pulse. Thereafter, the S&H circuit generates a continuous measurement that corresponds to the temperature of the PA during the remainder of the pulse. A Gain Control signal is generated that is a function of the difference between the initial temperature and the operating temperature of the PA as the PA self-heats for the duration of the pulse. The Gain Control signal is applied to one or more adjustable or tunable circuits within a PA to offset the Gain droop of the PA.

Techniques for limiting the output voltage of an amplifier without directly affecting an output current of the amplifier are provided. In an example, an amplifier can include a plurality of amplifier stages configured to receive an input voltage and to provide an output voltage as a function of the input voltage, and a comparator configured to receive a voltage limit and a representation of the output voltage of the amplifier, to adjust current at an input to a first amplifier stage of the plurality of amplifier stages when the output voltage violates the voltage limit, and to clamp the output voltage at an offset from the voltage limit.

A method and apparatus for a dual-feedback, amplifier limiter for providing a conditioned radio-frequency signal. The dual-feedback, amplifier limiter includes an input that receives a radio-frequency signal and a stacked amplifier including an input node coupled to the input, an output node, a first transistor configured as a common-base amplifier, and a second transistor configured as a common-emitter amplifier. The dual-feedback, amplifier limiter further includes an output coupled to the output node of the stacked amplifier. The output provides the conditioned radio-frequency signal. The dual-feedback, amplifier limiter further includes a radio-frequency feedback circuit coupled to the stacked amplifier. The radio-frequency feedback circuit includes a passive radio-frequency dependent reactive element in series with a radio-frequency feedback circuit resistor. The dual-feedback, amplifier limiter further includes an envelope control feedback circuit coupled to the stacked amplifier and including a current mirror and a reactive element loop filter.

A switching amplifier, such as a Class D amplifier, includes a current sensing circuit. The current sensing circuit is formed by replica loop circuits that are selectively coupled to corresponding output inverter stages of the switching amplifier. The replica loop circuits operated to produce respective replica currents of the output currents generated by the output inverter stages. A sensing circuitry is coupled to receive the replica currents from the replica loop circuits and operates to produce an output sensing signal as a function of the respective replica currents.

A current sense amplifier includes a first amplifier stage, a second amplifier stage, a switch, and a common-mode transient detector. The first amplifier stage has a first amplifier output, a second amplifier output, a first amplifier input, and a second amplifier input. The second amplifier stage has a third amplifier input coupled to the first amplifier output, and a fourth amplifier input coupled to the second amplifier output. The switch has a switch control input, a first switch terminal coupled to the third amplifier input, and a second switch terminal coupled to the fourth amplifier input. The common-mode transient detector circuit has a detector output, a first detector input and a second detector input. The detector output is coupled to the switch control input. The first detector input is coupled to the first amplifier input. The second detector input is coupled to the second amplifier input.

A Doherty amplifier includes a carrier amplifier amplifying a radio frequency signal, a peak amplifier amplifying a radio frequency signal and including a driver stage peak amplifier and a power stage peak amplifier receiving an output of the driver stage peak amplifier, a drive level detection circuit detecting a drive level of the carrier amplifier, a control circuit outputting a signal to set a bias of the driver stage peak amplifier based on a drive level signal indicating the drive level detected by the drive level detection circuit, and a generation circuit generating a current or a voltage in accordance with an operating state of the driver stage peak amplifier. An operating state of the power stage peak amplifier is controlled based on the current or the voltage generated by the generation circuit in accordance with the operating state of the driver stage peak amplifier.

Systems and methods according to one or more embodiments are provided for sensing a current at an output of a switching amplifier. In one example, a system includes a first transistor switch coupled to a load configured to conduct a current in the load responsive to a first pulse width modulated control signal and a second transistor switch coupled to the load configured to conduct the current in the load responsive to a second pulse width modulated control signal. The system further includes a sample and hold circuit coupled between the load and a current sensing circuit configured to sample a voltage at the second transistor switch for a pre-determined sample time period in response to a midpoint of a second pulse width modulated control signal time period, and configured to provide the sampled voltage to the current sensing circuit.

Temperature compensation circuits and methods for adjusting one or more circuit parameters of a power amplifier (PA) to maintain approximately constant Gain versus time during pulsed operation sufficient to substantially offset self-heating of the PA. Some embodiments compensate for PA Gain droop due to self-heating using a Sample and Hold (S&H) circuit. Other embodiments include bias compensation circuits that directly regulate a bias signal to an amplifier stage as a function of localized heating of one or more of amplifier stages. Such bias compensation circuits include physical placement of at least one bias compensation circuit element in closer proximity to at least one amplifier stage than other bias compensation circuit elements. One bias compensation circuit embodiment includes a temperature-sensitive current mirror circuit for regulating the bias signal. Another bias compensation circuit embodiment includes a temperature-sensitive element having a positive temperature coefficient (PTC) for regulating the bias signal.