Abstract: An envelope tracking power amplifier system time-aligns a supply voltage to an input signal to a power amplifier. The power supply operates in a static mode for low amplitude input signals and operates in a dynamic mode for high amplitude input signals. In the static mode, the power supply produces a substantially constant supply voltage independent of the amplitude of the input signal. In the dynamic mode the power supply produces a dynamically varying envelope tracking supply voltage based on the amplitude of the input signal. A first delay is determined based on portions of the input and output signals captured during static operation of the power supply and a second delay is determined based on portions of the input and output signals captured during dynamic operation. A delay mismatch is estimated based on a difference between the first and second delays.

Abstract: There are provided a high-frequency amplifier and a high-frequency module having a high efficiency for an extensive input modulated signal power, and base station/mobile wireless machines using the amplifier or the module. The high-frequency amplifier includes a circuit that detects an envelope of an input modulated signal; a control signal generator circuit (a voltage controlled circuit or a current controlled circuit) that can change a voltage or a current according to a given function on the basis of a magnitude of the detected envelope signal; and a diode clamped variable power circuit that connects a plurality of diode clamped circuits each including a diode, a transistor, and a DC power supply to one another.

Abstract: Power amplification devices are described, which are configured to amplify a radio frequency (RF) transmission signal. The power amplification device includes a voltage regulation circuit and a power amplification circuit. The voltage regulation circuit includes a voltage regulator that is operable to generate a regulated voltage from the supply voltage and a feedback circuit that sets a voltage adjustment gain of the voltage regulation circuit. To help prevent the voltage regulation circuit from saturating, the feedback circuit reduces the voltage adjustment gain in response to a voltage difference reaching a threshold voltage level. The voltage difference is between a voltage regulator control signal level of a voltage regulator control signal and the regulated voltage level of the regulated voltage.

Abstract: Embodiments disclosed in the detailed description relate to a pseudo-envelope follower power management system for managing the power delivered to a linear RF power amplifier. The pseudo-envelope follower power management system may include a switch mode power supply converter and a parallel amplifier cooperatively coupled to provide a linear RF power amplifier supply to the linear RF power amplifier. The pseudo-envelope follower power management system may include a charge pump configured to power the parallel amplifier. The charge pump may generate a plurality of output voltage levels. The charge pump may be either a boost charge pump or a boost/buck charge pump. The pseudo-envelope follower power management system may include an offset voltage control circuit configured to provide feedback to the switch mode power supply converter to regulate an offset voltage developed across a coupling device that couples the output of the parallel amplifier to the linear RF power amplifier supply.

Abstract: There is disclosed a method for determining the timing misalignment between a power supply and an output in an envelope tracking amplification stage, the method including the steps of: estimating a distortion parameter in the amplification stage; and determining a timing error in dependence on the estimated distortion parameter.

Abstract: The embodiments of the present invention disclose a high power-supply rejection ratio (PSRR) amplifier circuit. The amplifier circuit comprises a low dropout regulator, a negative charge pump and an amplifier. The output voltages of the negative charge pump and the low dropout regulators don't track the change of input voltage. Therefore the amplifier circuit has high PSRR.

Abstract: An amplifier circuit, comprising: an input, for receiving an input signal to be amplified; a power amplifier, for amplifying the input signal; a switched power supply, having a switching frequency, for providing at least one supply voltage to the power amplifier; and a dither block, for dithering the switching frequency of the switched power supply. The dither block is controlled based on the input signal. Another aspect of the invention involves using first and second switches, each having different capacitances and resistances, and using the first or second switch depending on the input signal or volume signal. Another aspect of the invention involves controlling a bias signal provided to one or more components in the signal path based on the input signal or volume signal.

Abstract: An apparatus on a single integrated circuit (IC) die includes a multiple stage power amplifier having at least first and second stages, a multiple stage voltage regulator for providing a regulated voltage signal to the at least first and second stages of the multiple stage power amplifier, a power coupler for providing a portion of a power output of the multiple stage power amplifier to a power detector, the power detector for developing a power detect signal, and a power control loop including at least the second stage and an output stage of the multiple stage power amplifier, the power coupler, the power detector, and at least one stage of the multiple stage voltage regulator, the power control loop controlling only the second stage and the output stage of the multiple stage power amplifier.

Abstract: An envelope amplifier includes an amplifier unit, a comparator unit and an output unit. The amplifier unit is made up of a first output section that outputs a first current in response to an amplitude of an input envelope signal, and a second output section. The second output section outputs a second current of a current value proportionate to a current value of the first current. Absolute value of the current value of the second current is greater than that of a current value of the first current. Comparator unit compares the current value of the first current. The output unit sums a current via an inductor derived from a current sustained or broken in response to a compared result of the comparator unit to the second current to deliver the resulting sum current at an output end. The first current is configured to be terminated without being delivered to the output unit (FIG. 1).

Abstract: A regulator with decreased leakage and low loss for a power amplifier is described. Switching circuitry is used to connect the regulator input bias to a bias control voltage when the power amplifier is to be operated in an on condition or to a voltage generator when the power amplifier is to be operated in an off condition.

Abstract: Embodiments disclosed in the detailed description relate to a pseudo-envelope follower power management system used to manage the power delivered to a linear RF power amplifier.

Abstract: An amplifier includes an envelope detection unit that detects an envelope of a transmission signal; a comparing unit that compares a voltage of the envelope with a reference voltage; a selecting unit that selects, in accordance with a comparison result obtained by the comparing unit, an amplifying element that amplifies the transmission signal from among a plurality of amplifying elements each having different operating power; a voltage control unit that controls, in accordance with the envelope, a voltage that is used to amplify the transmission signal in the amplifying element that is selected by the selecting unit; a current measuring unit that measures a current of a power supply that supplies the voltage that is controlled by the voltage control unit; and a reference voltage control unit that controls the reference voltage such that the current measured by the current measuring unit decreases.

Abstract: A headphone driver amplifier operative without an external negative voltage power supply, coupled directly to the headphone speakers without the need for DC coupling capacitors used for preventing DC reaching the headphones. An onboard power supply generates a negative voltage rail which powers the output amplifiers, allowing driver amplifier operation from both positive and negative rails. Since the amplifiers can be biased at ground potential (O volts), no significant DC voltage exists across the speaker load and the need for DC coupling capacitors is eliminated.

Abstract: A method includes amplifying a non-constant-envelope input signal using a main amplifier having a first gain that varies depending on a supply voltage of the main amplifier. A constant-envelope signal is amplified using a reference amplifier having a second gain that varies depending on the supply voltage of the reference amplifier. Both the main amplifier and the reference amplifier are operated using a same variable supply voltage whose amplitude varies over time. A gain control signal is produced so as to compensate for changes in the second gain of the reference amplifier that are caused by the variable supply voltage. The gain control signal is applied in compensating for variations in the first gain of the main amplifier.

Abstract: A Multi-Mode Multi-Band (MMMB) radio frequency (RF) power amplifier circuit operating at multiple frequency bands. The power amplifier circuit comprises a single wideband power amplifier having high output impedance which is configured to be equal to a load impedance of the load connected to the power amplifier circuit. A bias voltage applied to the wideband power amplifier is changed from a first value to a second value to provide a predetermined output power of the wideband power amplifier to the load with the output impedance of wideband power amplifier being equal to the load impedance. The power amplifier circuit also includes an individual harmonic filter for filtering each frequency band independently.

Abstract: Circuitry, which includes a linear amplifier and a linear amplifier power supply, is disclosed. The linear amplifier at least partially provides an envelope power supply signal to a radio frequency (RF) power amplifier (PA) using a selected one of a group of linear amplifier supply voltages. The linear amplifier power supply provides at least one of the group of linear amplifier supply voltages. Selection of the selected one of the group of linear amplifier supply voltages is based on a desired voltage of the envelope power supply signal.

Abstract: Apparatus and methods for voltage converters are provided. In one embodiment, a voltage conversion system includes a bypass circuit and a voltage converter including an inductor and a plurality of switches configured to control a current through the inductor. The bypass circuit includes a first p-type field effect transistor (PFET), a second PFET, a first n-type field effect transistor (NFET), and a second NFET. The first and second NFET transistors and the first and second PFET transistors are electrically connected between a first end and a second end of the inductor such that a source of the first PFET transistor and a drain of the first NFET transistor are electrically connected to the first end of the inductor and such that a drain of the second PFET transistor and a source of the second NFET transistor are electrically connected to the second end of the inductor.

Abstract: There is disclosed an arrangement comprising: a driver stage connected to receive an input signal and generate a drive signal; a transformer comprising: a first winding of a first side of the transformer, across which winding a voltage signal is developed in dependence on the drive signal; and a second winding of the first side of the transformer, coupled to the first winding, which exhibits across it a voltage signal related to the voltage across the first winding, by swingback; and a first controller for comparing the voltage exhibited in the second winding to a first threshold voltage, and for selecting a first or a second supply voltage for the arrangement in dependence on the comparison.

Abstract: An apparatus comprising an input, a control signal generator coupled to the input and having a control signal generator output, and an amplifier coupled to the control signal generator output, wherein a voltage supplied to the amplifier is switched based on the control signal generator output, and wherein the control signal generator output is based on a data signal in the input. Also included is an apparatus comprising circuitry configured to implement a method comprising detecting an incoming signal, calculating a derivative of the incoming signal, estimating a future incoming signal based on the derivative of the incoming signal and a time step, and providing the estimated future incoming signal to switch between a first supply voltage and a second supply voltage prior to or concurrent with an arrival of the future incoming signal at the switch, wherein the incoming signal and the future incoming signal are analog signals.

Abstract: Presently many audio chips suffer from pop issues, which is especially serious for single ended audio drivers. An audio pop is a disturbance in the output caused by a sudden transition of chip power, particularly when a chip is powered on or powered off. Furthermore, compensation networks included in the amplifiers on audio chips for stability offer a significant path for transmitting power disturbances to the output. Hence, circuitry is developed to suppress pops in the output stages of an amplifier.

Abstract: An audio amplifier circuit is described which comprises an operational amplifier. The operational amplifier receives an audio input signal and provides an output suitable for connecting a headphone, or a loudspeaker. A step-up converter is provided which supplies the operational amplifier. The audio amplifier is configured to operate in one of multiple operating modes, each of which uses a distinct supply voltage Vcc of the operational amplifier in the audio amplifier. Comparators are used to compare the output voltage of the operational amplifier with a first reference voltage to raise the supply voltage of the operational amplifier, if clipping is imminent. A second comparator is used to compare the output voltage of the operational amplifier with a second reference voltage, indicating that the supply voltage of the operational amplifier can be lowered without the risk of clipping.

Abstract: There is provided an amplifier circuit including: a first transistor having a source thereof connected to an input port and having a gate thereof grounded; a second transistor having a gate thereof grounded; a first inductor provided between a drain of the first transistor and a source of the second transistor; and a second inductor provided between a drain of the second transistor and an output port.

Abstract: A power control circuit for regulating an output voltage applied to a radio frequency power amplifier. The power control circuit includes an amplifier, a pass transistor and one or more saturation detectors. An input ramp voltage having a magnitude equal to a first voltage level is applied to a negative terminal of the amplifier. The pass transistor provides an output voltage at a drain terminal of the pass transistor. The saturation detector detects a magnitude of a voltage at a gate terminal of the pass transistor and generates a control current based on the magnitude of the voltage at the gate terminal of the pass transistor. The voltage regulating circuit reduces the magnitude of the input ramp voltage from the first voltage level to a third voltage level based on the control current.

Abstract: An apparatus of a hybrid power modulator using interleaving switching is provided. The apparatus includes a linear switching unit for generating an output signal by comparing an envelope input signal and a feedback signal, an interleaving signal generator for generating an interleaving switching signal arranged not to supply the signal to input stages of P-type Metal-Oxide-Semiconductor (MOS) Field Effect Transistors (FETs) and N-type MOS FETs of power cells at the same time by comparing the output signal and a reference signal, and a switching amplifying unit for determining a level of the switching signal using the interleaving switching signal. Hence, the hybrid power modulator using the interleaving switching method in the envelope signal of the wide bandwidth maintains high efficiency and high linearity. In addition, the buck converter can use the single inductor by preventing the simultaneous on/off of the power cells.

Abstract: An amplifier circuit comprises differential amplification circuitry comprising an input stage having first and second differential inputs, and an output stage, having respective first and second amplifier components with first and second differential outputs. The first amplifier component of the output stage comprises a first power transistor operably coupled to the first differential output and driven by a first differential output of the input stage, and a third power transistor operably coupled to the first differential output of the amplifier circuit and driven by a second output of the input stage. The second amplifier component comprises a second power transistor operably coupled to the second differential output and driven by a second output of the input stage, and a fourth power transistor operably coupled to the second differential output and driven by the first output of the input stage.

Abstract: A method of controlling power supply voltage of an audio amplifier delays an input audio signal; estimates, with a digital signal processor, an audio output level of the delayed input audio signal based on correlations between the delayed input audio signal level and audio level change factors; sets a value of power supply voltage supplied to a power switching circuit unit in correspondence with the estimated audio output level prior to outputting the delayed input audio signal on which the estimated audio output level is based; and amplifies the delayed audio input signal to provide an audio output signal by variably controlling the power supply voltage supplied to the power switching circuit unit according to the set value of power supply voltage.

Abstract: A radio frequency (RF) power amplifier system adjusts the supply voltage provided to a power amplifier (PA) adaptively, responsive to the measured or estimated power of the RF output signal of the PA. The RF PA system includes a power amplifier (PA) which receives and amplifies an RF input signal to generate an RF output signal at a level suitable for transmission to an antenna. A PA supply voltage controller generates a supply voltage control signal, which is used to control the supply voltage to the final stage of the PA. The supply voltage control signal is generated responsive to the measured or estimated power of the PA RF output signal, and also may be responsive to a parameter indicative of impedance mismatch experienced at the PA output. By controlling this supply voltage to the RF PA, the efficiency of the PA is improved.

Abstract: A power off delay circuit includes a switch connected between an external power input terminal and an internal power supply terminal, a capacitor connected to the internal power supply terminal, and a hysteresis comparator to switch the switch according to the voltages of the external power input terminal and the internal power supply terminal. During on-time of the switch, the external power input terminal is connected to the internal power supply terminal and the capacitor can be charged by the external power source. When the switch is off, the capacitor provides electric power for an internal circuit. Application of the power off delay circuit to an audio system may eliminate the turn-off pops of the audio system.

Abstract: The present invention relates to a power supply control network of an amplifying active elements system enabling at least one control signal to be transmitted to N different control systems of the power supply voltage of P different composed active amplifying elements. It comprises a set of distributor elements of power supply control signals connected in cascade.

Abstract: This current-voltage converter(22) with a current reflector, the input current including a fixed component and a variable component, includes: an input (24) for the current to be converted; an output (26) for the converted voltage; a resistor (36) for current-voltage conversion arranged between the output (26) and the ground, the input (24) being connected to the output (26) for the circulation of the current to be converted in the resistor (36); and a current reflector circuit (38) including two constant current sources (40, 42) , each connected between the output (26) and a respective reference voltage (32, 34). This converter (22) also includes a cascode stage (44, 46) , mounted in series with each constant current generator (40, 42) in order to impose a constant potential difference on the terminals of each constant current generator (40, 42) regardless of the output voltage.

Abstract: A distributed power converter is for use with an RF power amplifier and includes a primary converter connected to an input voltage and configured to provide an unregulated DC intermediate voltage that is galvanically isolated from the input voltage. Additionally, the distributed power converter also includes a secondary regulator connected galvanically to the unregulated DC intermediate voltage and configured to generate a regulated DC supply voltage for at least a portion of the RF power amplifier. In another aspect, a method of operating a distributed power converter is for use with an RF power amplifier and includes providing an unregulated DC intermediate voltage that is galvanically isolated from an input voltage and generating a regulated DC supply voltage for at least a portion of the RF power amplifier that is galvanically connected to the unregulated DC intermediate voltage.

Abstract: Disclosed are methods, circuits and systems for regulating the output power of a transmission system. There may be provided a power amplifier (“PA”) adapted to operate across a range of supply voltages. The PA may operate under different bias profiles. There may be provided power amplifier regulation circuitry which may include a PA bias profile generator adapted to generate one or more bias profiles, wherein a given bias profile is associated with a given bias signal for the PA. A bias profile associated with a given bias signal for a given PA may include one or more PA parameters or settings to be applied to the given PA when it is operating with the given bias signal.

Abstract: Methods and apparatus for a switchable balun for combined BLUETOOTH® and WLAN operation. A switchable balun is provided that includes an input circuit for receiving an amplified signal, the input circuit comprising first and second coils connected at a center tap, an output circuit comprising a third coil that is inductively coupled to the first and second coils, the output circuit for outputting an adjusted version of the amplified signal for transmission in a selected transmission mode, and a switch coupled to the center tap, wherein the switch is configured to couple a first voltage to the center tap to select operation in a first transmission mode and to couple a second voltage to the center tap to select operation in a second transmission mode.

Abstract: A signal amplifying circuit and associated methods and apparatuses, the circuit comprising: a signal path extending from an input terminal to an output terminal, a gain controller arranged to control the gain applied along the signal path in response to a control signal; an output stage within the signal path for generating the output signal, the output stage having a gain that is substantially independent of its supply voltage, and a variable voltage power supply comprising a charge pump for providing positive and negative output voltages, the charge pump comprising a network of switches that is operable in a number of different states and a controller for operating the switches in a sequence of the states so as to generate positive and negative output voltages together spanning a voltage approximately equal to the input voltage.

Abstract: A dynamic power supply for N amplifiers includes first and second power boost circuits which temporarily boost the positive or negative power supply rail, respectively. A control circuit monitors amplifier output signal levels and provides power boost control signals to the power boost circuits, which temporarily raise the positive supply voltage above the nominal voltage level in tandem with the highest output signal from the N amplifiers and lower the negative supply voltage below the nominal voltage level in tandem with the lowest output signal level from the N amplifiers. The power boost circuits each may be coupled to a reservoir capacitor from which current is drawn to provide the power boost. When inactive, the reservoir capacitors charge up from the respective power supply rails. The dynamic power supply is well suited for audio amplification systems.

Abstract: An amplifier circuit (10) comprises a driver stage (11) with a driver output (13). Moreover, the amplifier circuit (10) comprises a sensor (12). The sensor (12) comprises a variable attenuator (15) with a control input (16) for receiving a mode signal (SMODE). A sensor output (14) of the sensor (12) is coupled to the driver output (13) via the variable attenuator (15). A sensor signal (SE_RFOUT) is provided at the sensor output (14).

Abstract: Embodiments for at least one method and apparatus of a multi-use voltage regulator providing a supply voltage to a power amplifier and at least one other device are disclosed. One method includes generating a plurality of regulated voltage supplies from an unregulated voltage. An output signal power level of the power amplifier is determined. A one of the regulated plurality of voltage supplies and the unregulated voltage supply is selected as a power amplifier voltage supply for the power amplifier based at least in part on the output signal power level of the power amplifier. If the selected power amplifier voltage supply is one of the plurality of regulated voltage supplies, then the selected one of the plurality of regulated voltage supplies is simultaneously provided to the power amplifier and the at least one other device.

Abstract: A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

Abstract: A signal processing system and method utilizes a multi-stage amplifier to amplify an input signal. The multi-stage amplifier uses a mixed set of voltage rails to improve the operating efficiency of at least one of the amplification stages while allowing other amplification stages to operate in a predetermined operating mode. Efficiency of at least one of the stages is improved by supplying at least one variable voltage rail to an amplification stage of the multi-stage amplifier. The variable voltage rail varies in response to changes in an input signal voltage to the amplification stage. Accordingly, at least one amplification stage utilizes a variable voltage rail, and all amplification stages are supplied with a set of voltage rails that provides sufficient input signal headroom, thus, providing amplification stage efficiency and adequate voltage to allow operation of all amplification stages.

Abstract: An amplifier for amplifying a radio signal to a defined power output level is presented, wherein the amplifier comprises an amplifier input port, an amplifier output port, a first transistor for amplifying the radio signal received at a first transistor control input, wherein a first transistor output of the first transistor is supplied by a first power source; a at least second transistor for supplying the first transistor from a at least second power supply source. The at least second power supply source is added by the at least second transistor as a function of the power output level of the amplifier.

Abstract: A circuitry adapted to operate in a high-temperature environment of a turbine engine is provided. A relatively high-gain differential amplifier (102) may have an input terminal coupled to receive a voltage indicative of a sensed parameter of a component (20) of the turbine engine. A hybrid load circuitry may be coupled to the differential amplifier. A voltage regulator circuitry (244) may be coupled to power the differential amplifier. The differential amplifier, the hybrid load circuitry and the voltage regulator circuitry may each be disposed in the high-temperature environment of the turbine engine.

Abstract: An amplifier with high power supply rejection is disclosed. In an exemplary implementation, an amplifier includes a first stage configured to receive a signal to be amplified, a second stage comprising an input transistor coupled to the first stage, and further comprising at least one additional transistor, and a voltage regulator configured to received a first supply voltage and generate a regulated supply voltage, the first supply voltage coupled to the at least one additional transistor, the regulated supply voltage coupled to the first stage and the input transistor of the second stage to improve power supply noise rejection of the apparatus.

Abstract: A power amplifier using a drain (collector) power control loop in which the feedback signal is an estimated output power level computed with a linear summation of the output sensed voltage and current. Both RF and baseband voltage and current sensing are possible, and voltage-mode or current-mode signal processing are feasible. This control loop technique is applicable to any means of drain power control circuits such as: supply regulators, DC-DC converters and others. Voltage error amplifiers can be used in conjunction with voltage feedback network, while current error amplifiers can be used with current feedback networks. Regulator sharing between different bands may be used as an area and cost reduction solution. The linear voltage and current summation driven power control technique can be also applied to the gate (base) power control scheme. Similarly, voltage-mode and current-mode signal processing can be implemented.

Abstract: A power supply is disclosed herein. For example, the power supply can include a switching device and an aperture generator and control module. The switching device can be configured to down-convert an input voltage and pass the down-converted input voltage to an output voltage node. The aperture generator and control module can be configured to control the switching device. In response to a power efficiency of the power supply exceeding a predetermined threshold, the aperture generator and control module can deactivate the switching device and pass the input voltage to the output voltage node.

Abstract: A circuit for providing a reference voltage can be widely used in audio applications. However, at startup an abrupt start in the reference signal can cause undesirable audible artifacts. A circuit employing feedback of a reference voltage to control the charging of a capacitor which provides the reference voltage can be used to provide a smooth startup to the reference voltage. The circuit contains a differential pair for steering a fixed current source from one path to another as the reference voltage increases. The steered current can then be mirrored into one ore more current mirrors where the newly mirrored current can he squeezed to zero when the difference between a desired reference voltage and the reference voltage approaches zero. This newly mirrored current can he used to charge a capacitor which is used to provide the reference voltage.

Abstract: A relationship is established between measurable characteristics of the DC power input to a power amplifier and the RF output power level. A power circuit is configured to measure the input supply current to the power amplifier and to utilize the relationship between the input supply current and the applied input supply voltage to the output power level, thereby normalizing the output power of an amplified communication signal.

Abstract: A circuit includes a reference voltage generator configured to generate a first reference voltage and a second reference voltage, wherein the first reference voltage is higher than a half of a positive power supply voltage, and the second reference voltage is lower than the half of the positive power supply voltage. An n-type differential amplifier includes a first and a second NMOS transistor, wherein a gate of the first NMOS transistor is coupled to an input node, and a gate of the second NMOS transistor is configured to receive the first reference voltage. A p-type differential amplifier is operated by the positive supply voltage and includes a first and a second PMOS transistor. A gate of the first PMOS transistor is coupled to the input node, and a gate of the second PMOS transistor is configured to receive the second reference voltage.

Abstract: An active bias control circuit for an amplifier includes a low dropout regulator for providing a regulated voltage to provide an input current to the amplifier, and a current sense circuit responsive to the low dropout regulator for sensing a scaled down replica of the input current to the amplifier. An amplifier control circuit adjusts a control voltage to the amplifier in response to the sensed, scaled down replica of the input current to regulate the input current to the amplifier. A method for power up sequencing an amplifier for an active bias control circuit for the amplifier is also disclosed.

Abstract: An active bias control circuit for an amplifier includes a switch responsive to a supply voltage for providing an input current to the input of the amplifier, and a current sense circuit coupled to the switch for sensing a scaled down replica of the input current to the amplifier. A first amplifier control circuit is responsive to the current sense circuit for adjusting a first control voltage to the amplifier in response to the sensed, scaled down replica of the input current to regulate the input current to the amplifier. Circuitry for power up sequencing an amplifier for an active bias control circuit for the amplifier is also disclosed.

Abstract: An infrared light emitting diode circuit and related methods are disclosed. Exemplary features of embodiments comprise circuitry for controlling the voltage delivered to infrared light emitting diodes and for reducing the power consumption of the circuitry in the absence of audio signals to be transmitted.