Abstract: A power amplifying circuit includes a switching circuit, an amplifier and a load. The switching circuit receives a first supply voltage and a second supply voltage. When the switching circuit is in a first operation mode, the first supply voltage is provided to a node. When the switching circuit is in a second operation mode, the second supply voltage is provided to the node. The amplifier receives a first input signal and a second input signal, and outputs a first output signal and a second output signal from a first output terminal and a second output signal, respectively. The load includes a first inductor and a second inductor. The first inductor is connected between the node and the first output terminal. The second inductor is connected between the node and the second output terminal.

Abstract: Embodiments of a four-port isolation module are presented herein. In an embodiment, the isolation module includes a step-up autotransformer comprising a first and second winding that are electrically coupled in series at a center node. The first port of the isolation module is configured to couple an antenna to a first end node of the series coupled windings. The second port of the isolation module is configured to couple a balancing network to a second end node of the series coupled windings. The third port is configured to couple a transmit path to the center node. The fourth port is configured to couple a differential receive path across the first end node and the second end node. The isolation module effectively isolates the third port from the fourth port to prevent strong outbound signals received at the third port from saturating an LNA coupled to the fourth port.

Abstract: Embodiments of the disclosure may include a method and apparatus for improving the efficiency and extending the operation time between recharges or replacement batteries of a portable audio delivery system. The audio delivery system may include a processor, an audio processing device, a speaker, and a rechargeable power source. The audio delivery system is generally configured to generate and/or receive an audio input signal and efficiently deliver an amplified, high quality audio output signal to a user. In some embodiments of the disclosure, the audio processing device of the audio delivery system may include a switch mode power supply (SMPS), a signal delay element, an envelope detector, and a switching signal amplifier.

Abstract: In accordance with an embodiment, a circuit includes a low noise amplifier transistor disposed on a first integrated circuit, a single pole multi throw (SPMT) switch disposed on a second integrated circuit, and a bypass switch coupled between a control node of the low noise amplifier transistor and an output node of the low noise amplifier transistor. The SPMT switch couples a plurality of module input terminals to a control node of the low noise amplifier transistor, and the bypass switch including a first switch coupled between the control node of the low noise amplifier transistor and an intermediate node, a second switch coupled between the intermediate node and the output node of the low noise amplifier transistor, and a third switch coupled between the intermediate node and a first reference node. The first integrated circuit and the second integrated circuit are disposed on a substrate.

Abstract: A high-frequency amplifier circuit comprising a first and a second amplification units connected in cascade structure and so on. The first amplification unit includes an FET of a first conductivity type having a source terminal supplied with a first potential, and a first inductor connected to an intermediate potential line, and the second amplification unit includes an FET of a second conductivity type having a source terminal supplied with a second potential, and a second inductor connected to the intermediate potential line. The intermediate potential line is supplied with an intermediate potential between the first and second potentials. The first and second amplification units are supplied with bias voltages by a first and a second bias units, respectively. An operating current for the second bias unit is controlled on the basis of the intermediate potential.

Abstract: A circuit that includes a Darlington transistor pair having an input transistor and an output transistor configured to generate an output signal at an output node in response to an input signal received through an input node is disclosed. The circuit has a feedback coupling network coupled between the output node and the input node for feeding back to the input node a portion of an amplified version of the input signal that passes through the input transistor. The circuit further includes a bias feedback network that includes a bias transistor and a resistive network that consists of only resistive elements such that no inductors and no capacitors are provided within the bias feedback network.

Abstract: A circuit includes a bias circuit for a biased transistor. The bias circuit includes a master-slave source follower circuit, a reference transistor, and a bias circuit voltage output coupled to the biased transistor and configured to provide a bias voltage. The reference transistor has a transconductance substantially identical to a transconductance of the biased transistor. A signal ground circuit may be coupled between the biased transistor and one or more components of the bias circuit that do not generate significant return currents to a power supply ground. A method includes generating a current in a reference transistor according to a first voltage generated using a master source follower circuit, generating a second voltage substantially identical to the first voltage using a slave source follower circuit, and providing the second voltage to a biased transistor. The reference transistor has a transconductance substantially identical to a transconductance of the biased transistor.

Abstract: A biasing circuitry is disclosed. The biasing circuitry includes a biasing module, electrically connected to a power amplifier; and a control series, having an end electrically connected to a positive voltage, and another end electrically connected to the biasing module. The control series includes a switch unit, controlled by a control voltage to be on or off; and a voltage-drop unit, connected to the switch unit in series. The voltage-drop unit is configured to adjust a bias point of the power amplifier.

Abstract: The present disclosure is to improve the power added efficiency of a power amplifier at high output power. The power amplifier includes: a first capacitor with a radio frequency signal input to one end thereof; a first transistor whose base is connected to the other end of the first capacitor to amplify the radio frequency signal; a bias circuit for supplying bias to the base of the first transistor; and a second capacitor with one end connected to the base of the first transistor and the other end connected to the emitter of the first transistor.

Abstract: An apparatus for controlling a pulse width modulation (PWM) amplifier is disclosed. In one aspect, the apparatus includes a delay circuit configured to delay an input signal and provide the delayed input signal to the PWM amplifier. The apparatus also includes a controller configured to generate and provide a supply voltage to the PWM amplifier based at least in part on the input signal such that the PWM amplifier generates an output signal based at least partially on the delayed input signal and the supply voltage.

Abstract: A bias circuit comprises: a first circuit that comprises a first resistor and a decoupling capacitor; a bias voltage generation circuit that comprises a first transistor being connected to the first circuit; one or more switches; a first replica circuit comprising a second circuit and a second transistor, the second circuit comprising a second resistor and a capacitor, the second transistor being connected to the second circuit; a second replica circuit comprising a third transistor; a comparator that makes a comparison between a pseudo-bias voltage and a reference voltage; and a control circuit that controls the one or more switches on the basis of the comparison result to reduce the amount of the current flowing through the first transistor.

Abstract: The present disclosure is directed to an envelope tracking supply modulator for multiple PAs. The envelope tracking supply modulator is configured to provide, for each of the multiple PAs, a separate supply voltage that is modulated based on the envelope of the respective RF input signal to the PA. Each of the modulated supply voltages is constructed from a DC component and an alternating current (AC) component. The DC component for each modulated supply voltage is generated by a main switching regulator that is shared by the multiple PAs. In one embodiment, the AC component for each modulated supply voltage is generated by an auxiliary switching regulator that is shared by the multiple PAs and a separate linear regulator for each of the multiple PAs. In another embodiment, the AC component for each modulated supply voltage is generated by a separate buffer.

Abstract: An RF amplifier module that has a plurality of amplifiers wherein at least one of the amplifiers is powered via an envelope tracking module. The biasing input of at least one of the amplifiers is provided to the first amplifier to power the first amplifier to reduce power consumption. The first amplifier may also be powered via fixed biasing to provide greater stability of the module.

Abstract: Systems, circuits and methods related to low power efficiency improvement in multi-mode multi-band power amplifiers. In some embodiments, a power-amplifier (PA) system can include a first amplification path having one or more PAs configured to generate a high power radio-frequency (RF) signal from an input RF signal when in a high power mode. The PA system can further include a second amplification path having one or more PAs configured to generate a low power RF signal from the input RF signal when in a low power mode. The PA system can further include a switching circuit coupled to the first amplification path and the second amplification path. The switching circuit can be configured to allow amplification of the input RF signal through the first amplification path in the high power mode or the second amplification path in the low power mode.

Abstract: An amplifier having a pair of transistors arranged in a cascode amplifier arrangement serially connected to a first voltage source. A DC bias regulator is provided having: a DC bias circuit for producing a reference voltage at a control electrode of a first one of the pair of transistors: and a voltage combiner having a pair of inputs, a first of the pair of inputs being coupled to the reference voltage and a second one of the pair of inputs being coupled to the first voltage source. The DC bias regulator produces a DC bias voltage at a control electrode of a second one of the pair of transistors related to a combination of the reference voltage and the first voltage source.

Abstract: Apparatus and methods for controlling radio frequency (RF) switches are disclosed. Provided herein are apparatus and methods for controlling RF switches. In certain configurations, an RF system includes a charge pump for generating a charge pump voltage, an RF switch, a level shifter for turning on or off the RF switch, and a level shifter control circuit for controlling the level shifter. The charge pump receives a mode signal used to enable or disable the charge pump. Additionally, the level shifter receives power in part from the charge pump voltage, and controls the RF switch based on a switch enable signal. The level shifter control circuit receives the mode signal and biases the level shifter with a bias voltage that changes based on a state of the mode signal.

Abstract: There is disclosed a method for controlling a power amplifier capable of utilizing nonlinearity correction in a nearly steady operation status of non-linearity correction, in a periodical fast switching system in time domain. The method may comprise receiving a periodic switch signal indicating switch time of the periodical fast switching system; and providing, based on the periodic switch signal, a pre-bias signal with a pre-determined voltage amplitude to the power amplifier for a pre-determined time period before each downlink time slot to preheat a transistor of the power amplifier so as to compensate a temperature change of a die inside the transistor.

Abstract: An envelope tracking power amplifier is disclosed herein. The envelope tracking power amplifier includes a multi-mode bias modulator and a power amplifier. The multi-mode bias modulator generates an envelope-modulated bias voltage from the envelope signal of an radio frequency (RF) signal whose power is to be amplified by using a linear amplifier and a switching amplifier each having varying current driving capability in response to an operation mode control signal that determines any one of low-level mode and high-level mode. The power amplifier is biased in response to the envelope-modulated bias voltage, amplifies the RF signal, and outputs the amplified RF signal to an antenna.

Abstract: A differential dynamic charge pump circuit comprising; a first charging stage in series with a second charging stage; the first charging stage comprising a first circuit input for receiving an alternating clock signal; a second circuit input for receiving an inverted version of the alternating clock signal; a first output inverter arrangement configured to receive output voltages from upper and lower charge pump arrangements and having a first output and a second output for providing a dynamic differential output; the second charging stage comprising a first input and a second input configured to receive the output signal from the first stage; a second output inverter arrangement configured to receive output voltages from upper and lower charge pump arrangements and having a first output and a second output for providing a dynamic differential output of the circuit.

Abstract: A circuit for suppressing audio output noise and an audio output circuit are provided. The circuit for suppressing audio output noise includes: a detecting circuit, configured to detect output voltages of output stages of an audio power amplifier; a control circuit, configured to output at least one control signal, the control signal is related to detection results of the detecting circuit; and a compensating circuit, configured to compensate at least one output stage of the audio power amplifier which includes a differential circuit based on the at least one control signal output by the control circuit, to make parameters of the differential circuit symmetrical or approach symmetrical. Based on detection results of the output stage voltages, the differential circuit in the output stages of the audio power amplifier is compensated. The circuit for suppressing audio output noise has a wider application scope and it is easy to design the circuit.

Abstract: Various embodiments provide a radio frequency (RF) power amplifier (PA) circuit including an RF PA and a bias circuit. The bias circuit may provide a direct current (DC) bias voltage to the RF PA. The bias circuit may include a bias transistor, and the RF PA may include an amplifier transistor. The bias circuit may further include a diode coupled between a gate terminal of the amplifier transistor and a drain terminal of the bias transistor to pass the DC bias voltage to the gate terminal of the amplifier transistor and to level-shift the DC bias voltage at the gate terminal of the amplifier transistor to be higher than a DC voltage level at the drain terminal of the bias transistor.

Abstract: A scalable periphery digital power control arrangement is presented. The scalable periphery digital power control arrangement comprises a plurality of PMOS transistors connected in parallel, where the plurality of transistors is operatively coupled to a voltage source. The plurality of PMOS transistors that is operatively coupled to the voltage source can operate as a controlled current source. Current flow from the voltage source can be controlled by a logic circuit, which sends a logic signal to enable or disable each individual PMOS transistor of the plurality of PMOS transistors connected in parallel. As more PMOS transistors are enabled, the current flow through the scalable periphery digital power control arrangement to the amplifier can increase.

Abstract: This disclosure relates generally to power amplification devices and methods of operating the same. The power amplification devices are capable of reducing (and possibly cancelling) modulation of a ripple variation of a supply voltage level of a supply voltage onto a radio frequency (RF) signal. In one embodiment, a power amplification device includes a power amplification circuit configured to amplify an RF signal with a supply voltage such that a ripple variation in a supply voltage level of the supply voltage is modulated onto the RF signal in accordance with a conversion gain. However, the power amplification device also includes a plurality of ripple rejection circuits. The plurality of ripple rejection circuits is configured to produce phase shifts and one or more amplitude shifts in the RF signal so as to reduce the conversion gain of the power amplification circuit.

Abstract: An radio frequency amplifying circuit includes an amplifying transistor configured to amplify a radio frequency signal input to a base of the amplifying transistor via a matching network to output the amplified radio frequency signal, a first bias transistor connected to the amplifying transistor based on a current-mirror connection to supply a bias to the amplifying transistor, and a second bias transistor connected to the base of the amplifying transistor based on an emitter-follower connection to supply a bias to the amplifying transistor.

Abstract: A power amplification module includes a first transistor which amplifies and outputs a radio frequency signal input to its base; a current source which outputs a control current; a second transistor connected to an output of the current source, a first current from the control current input to its collector, a control voltage generation circuit connected to the output and which generates a control voltage according to a second current from the control current; a first FET, the drain being supplied with a supply voltage, the source being connected to the base of the first transistor, and the gate being supplied with the control voltage; and a second FET, the drain being supplied with the supply voltage, the source being connected to the base of the second transistor, and the gate being supplied with the control voltage.

Abstract: A receiver front end architecture for intra band carrier aggregation is disclosed. In an exemplary embodiment, an apparatus includes a first transistor having a gate terminal to receive an input signal, drain terminal to output an amplified signal, and a source terminal connected to a signal ground by a source degeneration inductor. The apparatus also includes a second transistor having a source terminal connected to the drain terminal of the first transistor and a drain terminal connected to a first load. The apparatus also includes a third transistor having a gate terminal connected to the drain terminal of the first transistor, a drain terminal connected to a second load and a source terminal connected to a signal ground.

Abstract: The invention provides an RF detection circuit and method using an envelope detector having an output connected to a first input of a differential amplifier and a reference storage capacitor to a second input of the differential amplifier. In a preferred implementation of the calibration mode, there is initial discharging of a reference storage capacitor, high speed charging of the reference storage capacitor until the differential amplifier output toggles, then slower discharging of the reference storage capacitor until the differential amplifier output toggles again. The resulting voltage is stored on the reference storage capacitor for use in a subsequent detection mode. This provides storage of an offset voltage which calibrates both the envelope detector differential amplifier functions.

Abstract: Power amplifier circuitry includes a power amplifier including an input node and an output node, biasing circuitry, a selectable impedance network, and an input capacitor. The input capacitor is coupled to the input node of the power amplifier. The biasing circuitry is coupled to the input node of the power amplifier through the selectable impedance network. The power amplifier is operable in a low power operating mode and a high power operating mode. In the low power operating mode, the biasing circuitry delivers a first biasing current to the input node of the power amplifier, and a first impedance level of the selectable impedance is selected. In the high power operating mode, the biasing circuitry delivers a second biasing current to the input node of the power amplifier, and a second impedance level of the selectable impedance is selected.

Abstract: The present disclosure provides a power amplifier controller for starting up, operating, and shutting down a power amplifier. The power amplifier controller includes current sense amplifier circuitry adapted to monitor a main current of the power amplifier. A bias generator is also included and adapted to provide a predetermined standby bias voltage and an operational bias voltage based upon a main current level sensed by the current sense amplifier circuitry. The power amplifier controller further includes a sequencer adapted to control startup and shutdown sequences of the power amplifier. In at least one embodiment, the power amplifier is a gallium nitride (GaN) device, and the main current level sensed is a drain current of the GaN device. Moreover, the bias generator is a gate bias generator provided that the power amplifier is a field effect transistor (FET) device.

Abstract: A receiver for a wireless device is described. The receiver includes a low noise amplifier that includes differential inputs. The receiver also includes a mixer coupled to the low noise amplifier. The receiver further includes second-order intermodulation reduction circuitry coupled to a stage subsequent to the low noise amplifier. The second-order intermodulation reduction circuitry provides a biasing of the differential inputs.

Abstract: A cascode amplifier includes: a first transistor having a gate to which a signal is input, a grounded source, and a drain; a second transistor having a gate, a source connected to the drain of the first transistor, and a drain; a load connected to the drain of the second transistor; a DC-DC converter supplying a supply voltage, which is variable according to output power, to the drain of the second transistor via the load; and a first bias circuit supplying a voltage, which is a function of the supply voltage, to the gate of the second transistor.

Abstract: An amplitude shift keying (ASK) modulation amplifier circuit includes a first amplifier to which a high frequency signal and a modulating signal are supplied, and that is configured to perform an amplification of the high frequency signal and an ASK modulation, and a second amplifier to which an output of the first amplifier and the modulating signal are supplied, and that is configured to perform an amplification of the output signal from the first amplifier and an ASK modulation. In some configurations, an amplification gain of the second amplifier is set higher than an amplification gain of the first amplifier.

Abstract: A power amplifier is smaller in size and limits input noise having a differential frequency. A power amplifier has an input terminal, an amplifying transistor, a bias circuit, a filter circuit, and an impedance matching circuit. The bias circuit supplies a bias to the signal input side of the amplifying transistor. The filter circuit removes noise at the signal input side of the amplifying transistor. The filter circuit has a matching resistor, a chip inductor, and a chip capacitor. Each of the chip inductor and the chip capacitor is a surface mount device. The matching resistor is located on a semiconductor substrate, has a first end connected to a connection point of two MIM capacitors, and a second end connected to a connection point of one of the MIM capacitors and the signal input side of the amplifying transistor.

Abstract: A semiconductor device, comprising first and second field effect transistors arranged in a cascode configuration: wherein the first field effect transistor is a depletion mode transistor; and wherein the second field effect transistor comprises a first source to gate capacitance and a second additional source to gate capacitance connected in parallel to the first source to gate capacitance. A power factor correction (PFC) circuit comprising the semiconductor device. A power supply comprising the PFC circuit.

Abstract: Radiated noises of an output pulse signal are reduced.

Abstract: A transmission apparatus comprises a signal generator that generates input signals of two or more bands of frequencies and outputs the generated input signals; a power amplifier that amplifies the input signals and outputs amplified signals; a branching filter that outputs branched signals for the respective frequencies from the amplified signals; a data transmitter that transmits data based on one of the branched signals of a first frequency; a power regenerator that converts one of the branched signals of a second frequency into regenerated power and output the regenerated power, and a power combiner that combines the regenerated power and power supply power output from a voltage source, as combined power and supplies the combined power to the power amplifier.

Abstract: A system for power amplifier over-voltage protection includes a power amplifier configured to receive a system voltage, a bias circuit configured to provide a bias signal to the power amplifier, and a power amplifier over-voltage circuit configured to interrupt the bias signal when the system voltage exceeds a predetermined value, while the system voltage remains coupled to the power amplifier.

Abstract: According to one embodiment, provided are an amplifier transistor configured to amplify an input signal; a biasing circuit configured to set a bias voltage in such a manner as to allow the amplifier transistor to perform amplification; an electrostatic protective circuit configured to set the bias voltage for the amplifier transistor in such a manner as to make the amplifier transistor to turn off based on voltage to be applied to the amplifier transistor; and a switching circuit configured to switch the bias voltage for the amplifier transistor based on a power supply condition.

Abstract: Embodiments provide a switching device including one or more cells. In embodiments, a cell may include a switch field-effect transistor (FET) and a source-follower FET, coupled between a gate and a body of the switch FET. Other embodiments may be described and claimed.

Abstract: To maintain linear operation of a signal processing circuit, such as a low noise amplifier, a peak detector detects a peak of a signal associated with the signal processing circuit and compares the detected peak signal with a threshold. When the detected peak signal is greater than the threshold, a fixed current source biases the signal processing circuit to place the signal processing circuit in a different mode of operation. The signal processing circuit may thereby process a larger input signal while operating in an acceptable linear region.

Abstract: An integrated circuit can comprise: a first port, a second port, and a third port; and a plurality of microwave operational amplifiers coupled to each other and the first port, the second port, and the third port. The plurality of microwave operational amplifiers can be arranged to substantially pass a signal provided to the first port to the second port while substantially isolating the signal provided to the first port from the third port; the plurality of microwave operational amplifiers can be arranged to substantially pass a signal provided to the second port to the third port while substantially isolating the signal provided to the second port from the first port; and the plurality of microwave operational amplifiers can be arranged to substantially pass a signal provided to the third port to the first port while substantially isolating the signal provided to the third port from the second port.

Abstract: A sensing circuit for a power FET. A first sensing FET senses current flow from load to ground. A second sensing FET senses current flow from ground to load. The current flows are converted to voltages, then added to generate a sensed output voltage. The specific amplitude of the sensed output voltage indicates the direction of the current flow. Resistive elements used to convert currents to voltages are configured as pairs of resistors having temperature coefficients of opposite polarity in order to compensate for temperature effects in the sensing circuit.

Abstract: In an aspect of the present invention, an ESD (Electrostatic Discharge) protection element includes a bipolar transistor comprising a collector diffusion layer connected with a first terminal and an emitter diffusion layer; and current control resistances provided for a plurality of current paths from a second terminal to the collector diffusion layer through the emitter diffusion layer, respectively. The bipolar transistor further includes a base diffusion region connected with the second terminal through a first resistance which is different from the current control resistances.

Abstract: A radio frequency (RF) power amplifier is disclosed. The RF power amplifier includes a bias circuit, an output stage circuit and dynamic bias controlling circuit. The bias circuit receives a first system voltage and provides a working voltage accordingly. The output stage circuit receives the working voltage so as to work at an operation bias point. The dynamic bias controlling circuit detects a RF input signal and outputs a compensation voltage to the bias circuit according to variation of the RF input signal, wherein the dynamic bias controlling circuit is an open loop configuration. When an input power of the RF input signal increases and makes the working voltage decreases so as to shift the operation bias point, the bias circuit adjusts the working voltage upward so as to recover or enhance the operation bias point according to the compensation voltage received.

Abstract: Devices and methods for correcting for start-up transients in integrated power amplifier are disclosed. A power amplifier is responsive to a bias control output and is arranged to provide an amplified power output. In some examples, the boost current is adjusted based on a supply voltage and an input power of the power amplifier. The power amplifier can operate in a low power and a high power mode and the adjustments can be made to the supply voltage and/or the input power vary depending on whether the power amplifier is operating in the high or low power mode. The adjustments for the high power mode operation are different than and correspond to the high power mode input power and voltage and the adjustments for the low power mode operation are different than and correspond to the low power mode input power and voltage.

Abstract: Devices and methods for correcting for start-up transients in integrated power amplifiers are disclosed. A delay element is arranged to produce a delay waveform signal that is responsive to an input voltage signal. A transconductance element has an input that receives the delay waveform signal and is arranged to provide an output boost current that is based on the delay waveform signal and a gain of the transconductance element. A reference element provides an output bias current that is responsive to a static reference current and the boost current. A bias element has an input that receives the bias current and is arranged to provide a bias control output. A power amplifier is responsive to the bias control output and is arranged to provide an amplified power output. In some examples, the boost current is adjusted based on a supply voltage and an input power of the power amplifier.

Abstract: A power amplifier includes: an amplifier having an input terminal and including an amplifying transistor having a threshold voltage; a transistor supplying a bias to the input terminal of the amplifier according to an on/off signal; a capacitor connected between the input terminal of the amplifier and a grounding point; a resistor connected between the input terminal of the amplifier and the grounding point, in parallel with the capacitor; and a diode connected in series with the resistor. The diode has a threshold voltage that is lower than the threshold voltage of the amplifying transistor.

Abstract: There are provided a bias circuit and an amplifier having a current limit function, including: a control voltage generating unit generating a control voltage using a reference voltage; a bias voltage generating unit generating a bias voltage according to the control voltage; and a bias current limit unit controlling the control voltage according to a bias current of the bias voltage generating unit.

Abstract: There are provided a bias circuit and a power amplifier. The bias circuit includes a first temperature compensating unit connected between an operating voltage terminal and a ground and operating according to a reference voltage to generate a turn-on voltage, a second temperature compensating unit connected between a reference voltage terminal and the ground and operating according to the turn-on voltage to generate a control voltage, a power mode selecting unit selecting one of a high power mode and a low power mode and providing an additional current to the first temperature compensating unit at the time of selecting the low power mode to increase the turn-on voltage, and a bias voltage generating unit generating a bias voltage according to the control voltage, wherein the control voltage and the bias voltage are decreased according to the increase in the turn-on voltage.

Abstract: A power amplifier module that includes a power amplifier and a controller is presented herein. The power amplifier module may include a set of transistor stages and a plurality of bias circuits. At least one transistor stage from the set of transistor stages may be in electrical communication with a first bias circuit and a second bias circuit from the plurality of bias circuits. The first bias circuit can be configured to apply a first bias voltage to the at least one transistor stage and the second bias circuit can be configured to apply a second bias voltage to the at least one transistor stage. The controller may be configured to activate one of the first bias circuit and the second bias circuit.