Abstract: An apparatus for noise reduction in audio signal processing includes a power amplifier, a zero-crossing detector, and a threshold detector. The power amplifier has an input signal terminal for receiving an audio input signal and an output signal terminal. The audio input signal is a digital-to-analog converted version according to a version of a digital audio signal. The power amplifier has an analog gain which is controllable in response to an analog gain control signal. The zero-crossing detector determines a zero-crossing detection signal according to an internal signal provided between the input signal terminal and the output signal terminal. The threshold detector determines a gain setting according to the digital audio signal and the zero-crossing detection signal to generate the analog gain control signal indicating the gain setting, wherein the threshold detector controls the analog gain of the power amplifier according to the analog gain control signal.

Abstract: A power amplifier circuit includes a first amplifier transistor, an input signal being supplied to a base of the first amplifier transistor, a first amplification signal obtained by amplifying the input signal being output from a collector of the first amplifier transistor; a first bias circuit that supplies a first current or a first voltage to the base of the first amplifier transistor; a second bias circuit that supplies a second current or a second voltage to the base of the first amplifier transistor; and a first resistor element that is connected in series between the base of the first amplifier transistor and the first bias circuit. The second bias circuit includes a diode, an impedance circuit, and a first capacitor element.

Abstract: Embodiments of the disclosure relate to a frequency selective low noise amplifier (LNA) circuit, which includes a transconductive LNA(s). In one aspect, filter circuitry is provided in a degeneration path of a transconductive LNA(s) to pass in-band frequencies and reject out-of-band frequencies by generating low impedance and high impedance at the in-band frequencies and the out-of-band frequencies, respectively. However, having the filter circuitry in the degeneration path may cause instability in the transconductive LNA. As such, a feedback path is coupled between an input node of the transconductive LNA(s) and the degeneration path to provide a feedback to improve stability of the transconductive LNA(s). In addition, the feedback can help improve impedance match in the frequency selective LNA circuit. As a result, the transconductive LNA(s) is able to achieve improved noise figure (NF) (e.g., below 1.5 dB), return loss, linearity, and stability, without compromising LNA gain.

Abstract: Provided is a method and device for reducing the power consumption of a mobile terminal. The method for reducing the power consumption of the mobile terminal includes the following steps: the current transmitting power of the mobile terminal and the current gain switching point of a power amplifier are obtained; when the difference between the obtained current transmitting power and the current gain switching point is less than a preset gain difference, the current gain switching point of the mobile terminal is increased by a first preset value.

Abstract: The invention concerns an antenna system of a radio microphone that includes an antenna path starting at an in port and ending at an out port along with an amplifier and a radio frequency (RF) cable. In order to compensate for various cable attenuations, an attenuator is provided in series with a variable slope compensator between the amplifier and the RF cable. In order to avoid a negative effect on a large signal behavior of variable slope compensators, field effect transistors (FETs) or pin diodes are used for switching of the resistances so that a large signal behavior is achieved.

Abstract: A method for power amplifier (PA) calibration for an envelope tracking system of a wireless device is disclosed. The method involves measuring an output power of a PA that is a part under test (PUT) at a predetermined input power. Another step includes calculating a gain equal to the output power of the PA divided by the predetermined input power. A next step involves calculating a gain correction by subtracting the calculated gain from a desired gain. Other steps include determining an expected supply voltage for the PA at the desired gain using the gain correction applied to a nominal curve of gain versus PA supply voltage, and then storing the expected supply voltage for the PA versus input power in memory.

Abstract: Apparatus and methods for envelope tracking calibration are provided. In one embodiment, a method of calibrating an envelope tracker having an envelope shaping table generated at a desired gain compression of a power amplifier is provided. The method includes generating a supply voltage for the power amplifier using the envelope tracker, operating the supply voltage of the power amplifier at a first voltage level associated with substantially no gain compression of the power amplifier, and measuring an output power of the power amplifier at the first voltage level. The method further includes decreasing a voltage level of the supply voltage one or more times and measuring the output power at each voltage level, determining a second voltage level of the power amplifier associated with a gain compression equal to about that of the desired gain compression, and calibrating the envelope tracker based on the determination.

Abstract: The exemplary embodiments include methods, computer readable media, and devices for calibrating a non-linear power detector of a radio frequency device based upon measurements of the non-linear power detector output and the associated power amplifier output level, and a set of data points that characterize a nominal non-linear power detector. The set of data points that characterize the nominal non-linear power detector is stored in a calibration system memory as nominal power detector output data. The measured non-linear power detector outputs, power amplifier output levels, and the nominal power detector output data is used to determine a power detector error function that characterizes the difference between the response of the non-linear power detector and the nominal non-linear power detector. The power detector error function and the nominal power detector output data are used to develop a calibrated power detector output data set that is stored in the non-linear power detector.

Abstract: A polar modulator of the present invention includes: a first function block which generates an amplitude signal and a phase signal; a second function block which adjusts the signal delay between the amplitude signal and the phase signal; a third function block which allows the low frequency component of the amplitude signal to pass therethrough; a fourth function block which modulates the phase of the phase signal; a fifth function block which outputs a modulation voltage, based on the amplitude signal; a sixth function block which modulates the amplitude of the phase signal, based on the modulation voltage; a seventh function block which measures the temperature of at least one function block; and an eighth function block which calculates a compensation amount for the signal delay, based on the measured temperature. The second function block adjusts the signal delay, based on the compensation amount.

Abstract: Techniques for dynamically generating a headroom voltage for an envelope tracking system. In an aspect, an initial headroom voltage is updated when a signal from a power amplifier (PA) indicates that the PA headroom is insufficient. The initial headroom voltage may be updated to an operating headroom voltage that includes the initial voltage plus a deficiency voltage plus a margin. In this manner, the operating headroom voltage may be dynamically selected to minimize power consumption while still ensuring that the PA is linear. In a further aspect, a specific exemplary embodiment of a headroom voltage generator using a counter is described.

Abstract: Techniques for preventing reverse current in applications wherein a tracking supply voltage is placed in parallel with a switching power stage. The tracking supply voltage may be boosted to a level higher than a battery supply voltage using, e.g., a boost converter. In an aspect, a negative current detection block is provided to detect negative current flow from the boosted tracking supply voltage to the battery supply voltage. A high-side switch of the switching power stage may be disabled in response to detecting the negative current. To prevent false tripping, the tracking supply voltage may be further compared with the battery supply voltage, and a latch may be provided to further control the high-side switch.

Abstract: A method for calibrating a supply voltage of an envelope tracking PA (power amplifier) is provided. The method includes obtaining a plurality of calibrated PA supply voltage values using a PA output power sequence having a plurality of different PA output power values. Thereby, an order of the PA output power values of the PA output power sequence is chosen such that a junction temperature of the PA is maintained during calibration within a temperature range that occurs during non-calibration envelope tracking operation.

Abstract: An amplifier circuit includes a gain controller, a first amplifier, and a second amplifier which is coupled in series to the first amplifier, the second amplifier comprising a plurality of amplifying units.

Abstract: The problem to be solved is to alleviate the distortion characteristic of an amplifier and to prevent the drop in gain with respect to a low-level high-frequency signal. A bias control circuit (10) for controlling the bias of an amplifier (20) which amplifies a high-frequency signal is provided herein with a detector (11) for detecting the envelope of the high-frequency signal, a first bias circuit (12) for supplying a constant bias current to the amplifier (20) and a second bias circuit (14) for supplying a bias current that varies with the variation of the level of the envelope of the high-frequency signal to the amplifier.

Abstract: Disclosed herein is a gain control circuit including: an amplifying section configured to amplify an input voltage in such a manner that amplitude of an output voltage at an output terminal is kept constant; an allowable voltage acquirer configured to acquire an allowable voltage of an apparatus connected to the output terminal; a voltage divider configured to divide the output voltage according to a ratio between a maximum voltage of the amplified input voltage and the allowable voltage; and an adjusting section configured to further amplify the amplified input voltage according to the ratio and supply a resulting voltage to the output terminal.

Abstract: A method and an apparatus for controlling a transmit signal of a radio frequency power amplifier are provided. The method includes: adjusting a power supply voltage of the power amplifier to an efficiency point power supply voltage under designated transmit power; querying correspondence between an input voltage and transmit power at each power level under the efficiency point power supply voltage; and adjusting, according to the correspondence, an input voltage to an input voltage corresponding to the designated transmit power. The embodiments of the present invention, the power amplifier is enabled to work at an optimum efficiency point while the transmit power of the power amplifier is under control, which improves efficiency of the power amplifier.

Abstract: A digitally-controlled analog gain circuit supports a plurality of gain settings in which gain changes are made from a first setting to a new setting in response to a clocking signal. Large changes in gain are interpolated in small gain steps or increments. The clocking signal can be generated by an oscillator, or as a sequence of pulses output by a zero crossing detector. The gain circuit can apply positive gain to the signal. Alternatively, the gain circuit can apply a negative gain (attenuation) to the signal. The clocking signal can be provided in a pseudo-randomized manner to minimize unwanted signal effects such as discernable sound transients.

Abstract: In an automatic gain control circuit, a peak detection circuit detects and outputs the peak voltage of an output signal from a variable gain circuit. An average value detection/output amplitude setting circuit detects the average value voltage of an output signal from the variable gain circuit, and outputs a calculated voltage. An amplification circuit controls the gain of the variable gain circuit by amplifying the difference between the output voltages of the peak detection circuit and average value detection/output amplitude setting circuit. The number of base-emitter junctions of transistors on a path in the peak detection circuit from input ports which receive output signals from the variable gain circuit to an output port which outputs a voltage to the amplification circuit is equal to the number of base-emitter junctions of transistors on a path in the average value detection/output amplitude setting circuit.

Abstract: A drain modulator circuit for operation with a radio frequency (RF) amplifier, includes a pair of AC signal sources each of the AC signal sources having an output at which an AC signal is provided. The drain modulator circuit further includes a pair of tapped delay elements, each of which is configured to receive an AC signal from a respective one of the AC signal sources and a control element coupled to provide one or more control signals to the pair of tapped delay elements such that the tapped delay elements provide a selected instantaneous differential voltage to the RF amplifier.

Abstract: A method for power amplifier (PA) calibration for an envelope tracking system of a wireless device is disclosed. The method involves measuring an output power of a PA that is a part under test (PUT) at a predetermined input power. Another step includes calculating a gain equal to the output power of the PA divided by the predetermined input power. A next step involves calculating a gain correction by subtracting the calculated gain from a desired gain. Other steps include determining an expected supply voltage for the PA at the desired gain using the gain correction applied to a nominal curve of gain versus PA supply voltage, and then storing the expected supply voltage for the PA versus input power in memory.

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: An apparatus for implementing a front end circuit for a transimpedance amplifier includes a front end core that receives an input signal from a photo diode. The front end core responsively generates a balanced output signal to downstream devices. A power supply provides a supply voltage to the front end circuit. In accordance with the present invention, a current source is located between the supply voltage the front end core to thereby isolate the front end core from disturbances on the power supply. This biasing arrangement advantageously provides an improved power supply rejection ratio for the front end circuit.

Abstract: Apparatus and methods for envelope tracking calibration are provided. In one embodiment, a method of calibrating an envelope tracker having an envelope shaping table generated at a desired gain compression of a power amplifier is provided. The method includes generating a supply voltage for the power amplifier using the envelope tracker, operating the supply voltage of the power amplifier at a first voltage level associated with substantially no gain compression of the power amplifier, and measuring an output power of the power amplifier at the first voltage level. The method further includes decreasing a voltage level of the supply voltage one or more times and measuring the output power at each voltage level, determining a second voltage level of the power amplifier associated with a gain compression equal to about that of the desired gain compression, and calibrating the envelope tracker based on the determination.

Abstract: A switched current resistor (SCR) PGA for constant-bandwidth gain control includes an inverting amplifier, a feedback resistor forming a feedback loop between an output side and an input side of the inverting amplifier, and a switched current resistor (SCR) array connected in parallel to the feedback resistor, and configured to tune a gain range between a maximum and a minimum. The SCR array includes a plurality of switched resistors, each comprising a switch in series with a resistor. When the plurality of switched resistors are switched by a gain-control logic, a plurality of switched current sources and a plurality of grounded resistors are switched correspondingly to deliver a transient current, an equivalent of which flows through the plurality of grounded resistors out from the input side of the inverting amplifier, leading to a feedback factor of the PGA being constant.

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: Provided is a transmission circuit capable of compensating a variation in output power caused due to a temperature change or an individual variability when the operation mode is switched without an increase in the size of the transmission circuit which switches the operation mode between a linear operation mode and a nonlinear operation mode, and capable of suppressing the deterioration of the quality of a transmission signal. In the transmission circuit, a gain setting section (160) sets the gain (target gain) of a variable gain amplifier (140), to a value which enables the variable gain amplifier (140) to operate linearly and corresponds to a comparison result (output error level) obtained through comparison between the target level of the variable gain amplifier (140) corresponding to the set power level of the transmission signal and the power level of an output signal of the variable gain amplifier (140) detected by a power detection section (150).

Abstract: Provided is a power amplification circuit capable of quickly and highly accurately preventing an output power and a current of a power amplifier from fluctuating when an antenna load changes. A power amplifier 11 amplifies a radio frequency signal and obtains an output signal. A regulator 12 amplifies an input voltage by a predetermined gain and supplies an output voltage to the power amplifier 11. A current monitor 13 monitors an input current to the regulator 12 and obtains a monitor current. A first multiplier 14 multiplies the monitor current by the output voltage of the regulator 12 and obtains a monitor power. A memory 16 prestores a predetermined reference current. A second multiplier 15 multiplies the input voltage by the reference current and obtains a reference power. A gain control section 121 in the regulator 12 controls a predetermined gain based on the monitor power and the reference power.

Abstract: There is provided a power amplifier that can maintain a constant gain by detecting a level of a signal being input and a level of a signal being output. A power amplifier according to an aspect of the invention may include: an amplification section having at least one amplification unit amplifying an input signal according to an adjustable gain to thereby output the amplified input signal; a detection section detecting signal levels of an input signal and an output signal of the amplification section; and a gain maintaining section controlling a bias power according to a detection result of the detection section so that a gain of the amplification section is maintained within a predetermined gain range.

Abstract: Disclosed is a power amplifier apparatus including: an amplifier amplifying an input modulated signal; a control signal generator receiving an amplitude component of the input modulated signal and generating a control signal; and a power combiner performing ON/OFF control of a switching element based on the control signal to control conduction and non-conduction of a current supplied from a second power supply. In the power combiner, a power of a pulsed form when the current from the second power supply is conductive is transferred in a direction of a first power supply, using a transformer. A difference power obtained by subtracting a constant value from a first power supply voltage when the amplitude of the input modulated signal is smaller than that of a reference signal is supplied from the power combiner to the amplifier, as a power supply thereof (FIG. 1).

Abstract: A highly efficient class-G amplifier includes an amplifier circuit coupled between a positive power rail and a negative power rail to amplify an audio input signal of the class-G amplifier, and a boost inverting power converter to convert a supply voltage to a positive rail voltage and a negative rail voltage on the positive and negative power rails. The boost inverting power converter includes a boost inverting power stage coupled to the positive and negative power rails, and a controller to switch the boost inverting power stage between a boost mode and an inverting mode. An audio level detector detects the audio input signal for the controller to adjust the positive and negative rail voltages. The class-G amplifier has higher efficiency and requires lower cost because it does not need a charge pump.

Abstract: A digitally-controlled analog gain circuit supports a plurality of gain settings in which gain changes are made from a first setting to a new setting in response to a clocking signal. Large changes in gain are interpolated in small gain steps or increments. The clocking signal can be generated by an oscillator, or as a sequence of pulses output by a zero crossing detector. The gain circuit can apply positive gain to the signal. Alternatively, the gain circuit can apply a negative gain (attenuation) to the signal. The clocking signal can be provided in a pseudo-randomized manner to minimize unwanted signal effects such as discernable sound transients.

Abstract: A power amplifier controller circuit controls an adjustable impedance matching network at the output of a power amplifier to vary its load line to improve the efficiency of the RF PA. The PA controller circuit comprises an amplitude control loop that determines an amplitude correction signal. The amplitude loop is configured to control or correct for distortion from the adjustable matching network based upon the amplitude correction signal.

Abstract: An apparatus and method for controlling a high power amplifier in a communication system are provided. The apparatus includes a Radio Frequency (RF) power detection unit for detecting an intensity of an RF input signal, a high power amplifier controller for determining a control signal, which indicates a voltage value of a drain bias to be provided to at least one drain node from among drain nodes of a drive amplifier and a main amplifier included in the high power amplifier, according to the detected intensity, a Direct Current (DC) voltage supplying unit for generating a DC voltage corresponding to the determined control signal, a drain bias connection unit for providing the generated DC voltage to said at least one drain node from among the drain nodes of the drive amplifier and the main amplifier, and the drive amplifier and the main amplifier for amplifying the RF input signal according to the provided DC voltage.

Abstract: Techniques for optimizing the power consumption of existing low cost multi-gain state power amplifiers (PA) to increase the talk time of wireless communication devices are described. In an exemplary embodiment a device, such as a baseband processor, operates to set a multistage PA having at least two gain states for amplifying a transmit signal to a lowest power consuming gain state. The device calculates a transition power level as a function of an identified maximum power reduction (MPR) value and switches the PA to a higher gain state from a lower gain state when a transmission power level is higher than the calculated transition power level.

Abstract: A receiver capable of performing optimum automatic gain control responsive to a peak factor of an input signal before subjected to A/D conversion is provided in a simple configuration. A peak detector 104 is placed at the later stage of a variable gain amplifier 102, two power determiners 107 and 108 different in threshold value are used, and the amplitude density is determined in three areas separated by two threshold values PDETL and PDETH, whereby it is made possible to identify the input signal having a peak factor different in modulation system and perform optimum gain control without A/D conversion of the input signal.

Abstract: A reconfigurable power amplifier includes at least one amplification circuit (E1, E2), and a circuit (6) for controlling the amplification circuit so as to adapt its operation according to an applied input signal (RFin). The circuit for controlling includes a circuit (4, 5) for modifying the compression point of the amplification circuit and for adapting the gain of the amplification circuit in such a manner as to increase the power added efficiency of the circuit for the modified compression point.

Abstract: A power amplifier controller controls a power amplifier and is coupled to a polar modulator. The polar modulator generates an amplitude component and a phase-modulated component of the desired RF modulated signal, and outputs to the power amplifier controller. The power amplifier controller regenerates a combined phase and amplitude modulated RF signal to generate an input signal to a power amplifier by adjusting the gain of a VGA based on the amplitude component of the desired RF modulated signal. Concurrently, the power amplifier controller both controls an adjusted supply voltage to the PA and adjusts the gain of the VGA based upon an amplitude correction signal or amplitude error signal.

Abstract: An apparatus for a High Power Amplifier (HPA) in a wireless communication system is provided. In one example, the apparatus includes a temperature sensor for determining temperature, a controller for receiving the determined temperature and for controlling a gate bias voltage corresponding to the determined temperature and an amplifier for amplifying a Radio Frequency (RF) signal by using the controlled gate bias voltage.

Abstract: The transmission apparatus and transmission power controlling method are able to keep high speed feedback control and control transmission power accurately. Polar modulation transmitter (100) is provided with LPF (108) that performs waveform shaping of output power of PA (103) and ADC (109) that obtains output power data for each mode by sampling filtered signals in compressed mode and filtered signals in uncompressed mode at the same phase as the filtered signals in compressed mode. In this way, the phases of sampling signals before and after the mode change are the same, so that it is possible to obtain sampling signals of the same condition before and after the mode change, from filtered signal waveforms. According to feedback control based on these sampling signals, even if drift components remain in the filtered signals, the influence can be ignored, so that it is possible to keep high speed feedback control, and estimate and control transmission power accurately.

Abstract: An apparatus for and method of extending the dynamic range of a RF communications receiver. The invention provides a mechanism for controlling the gain of both the LNA and down conversion mixer in the front end portion of an RF receiver. Both the LNA and the mixer are adapted to have both low and high gain modes of operation. The control mechanism typically comprises a two bit gain control that places both the LNA and mixer in one of four operating gain mode states. The selection of the most appropriate operating gain mode state, is preferably determined in accordance with various metrics such as the received levels of the desired signal, levels of interference signals, bit error rate and receiver RSSI.

Abstract: A signal processing system has a first, digitally controlled, gain element, a second, analogue controlled, gain element and a gain control unit configured to receive a gain request signal and to generate a first gain control signal to be input to the first gain element and a second gain control signal to be input to the second gain element such that the gain provided by the signal processing system corresponds to the gain request signal.

Abstract: A low noise amplifier is provided for the receiver of a wireless communications system. The amplifier incorporates an image rejection function by incorporating a notch filter formed by an inductor and capacitor connected at a node between two active elements of the amplifier. The amplifier also incorporates a gain control function by adding a further active element connected to, on one hand, a node between the inductor and capacitor and, on the other hand, a voltage supply. A gain control signal is connected to the control input of the further active element has an input connected to a feedback lead of the receiver to provide the gain control.

Abstract: A coupling apparatus (1) having a mains connection (2) for connection to a low-voltage mains power supply system, and having an appliance connection (3) for connection of any appliance for transmitting and/or receiving an RF signal has a voltage converter (5) and a high-pass filter (6.1, 6.2). The voltage converter converts the mains voltage which is present at the mains connection to a very-low voltage, which is suitable for supplying the appliance connected to the appliance connection. Inductances (4.3 to 4.6) of suitable size are interposed in the appropriate connecting lines as low-pass filters for decoupling the RF signal path from the supply signal path, and for suppressing undesirable, radio-frequency signal components in the supply voltages. RF signals which are transmitted or are to be transmitted via the low-voltage mains power supply system are coupled from the mains connection via the high-pass filter to the appliance connection, and from the appliance connection to the mains connection.

Abstract: A power amplifier includes drains and sources of a plurality of transistors connected to each other to produce a plurality of common drains and a plurality of common sources, wherein the common drains are connected at a common drain point and wherein the common drain point is connected via an RF choke to a power supply voltage terminal and wherein the common sources are grounded; an output terminal connected to the RF choke; a plurality of bias terminals each coupled via a resistor to the gate of one of the plurality of transistors wherein each of the gates of the plurality of transistors is also capacitively coupled to a radio frequency input.

Abstract: A vertical amplifier system for a multitrace oscilloscope including a first and a second variable gain amplifiers each connected to each channel of a multitrace oscilloscope. First, a first reference voltage is fed to the two variable gain amplifiers at the same time. The polarity of output of the second variable gain amplifier is inverted, and the inverted output is added to the output of the first variable gain amplifier by an adder. The added result is detected by a resistor. A CPU automatically controls a gain of at least one of the variable gain amplifiers while receiving the added result so that the added result becomes zero. Second, a second reference voltage (a ground level voltage, for example) is applied to both variable gain amplifiers, and an offset of at least one of the variable gain amplifiers is adjusted so that the added result detected by the resistor becomes zero. The input-output characteristics of both variable gain amplifiers are equalized with high accuracy.

Abstract: A controlled-output power amplifier (50) is provided having a wide dynamic range in a plurality of output power levels. The controlled-output amplifier (50) includes an amplifier (12) for receiving an input signal (14) and for providing an output signal (16) therefrom. A power detector (24) is employed for rectifying a sample signal and providing a DC output signal (26) therefrom. An active variable coupling network (52) which preferably includes a varactor (62) is connected between the output of the amplifier (12) and the power detector (24). The variable coupling network (52) receives the amplifier output signal (16) and further receives an isolation voltage (54) and adjusts the amount of isolation between the amplifier (12) and the power detector (24). For high output signals, the isolation voltage (54) causes a high isolation thereby causing less power to be transferred to the power detector (24).

Abstract: In a digital radio telephone transmitter an output pulse with e.g. cos.sup.2 -shaped edges is produced by a voltage controlled power amplifier (4). When known control loop circuitry is used, the power (Pout) of the output pulse will rise almost step-wise at the beginning of the pulse, which leads to the spreading of the spectrum and to rise time delays of the output pulse with respect to the control pulse (TXC) at different power levels. According to the invention a good cos.sup.2 -shape of the output pulse (Pout) and its tracking of the control pulse (TXC) almost without delay is achieved so that a squarewave pulse (V.sub.p) is added to the control voltage (V2) of the power amplifier (4), the pulse (V.sub.p) starting and ending substantially at the same time as the control pulse (TXC). In a preferred embodiment the squarewave pulse (V.sub.p) is added to the control voltage (V2) only during that time when the control voltage (V2) is below that value, at which the control loop begins to operate.

Abstract: The clipping suppression arrangement for a compandorized communication system, includes a limiter peak level detector for causing the gain of an input amplifier to be reduced quickly when a compressed output is driven toward a clipping output condition.

Abstract: A nonlinear signal transducer U, such as a light-emitting diode or a semiconductive laser, is maintained at a suitable operating point by a constant biasing current and receives an electrical input signal by way of a series resistor R from a main amplifier AM of variable gain. The output voltage of the main amplifier is detected and integrated to provide a first reference voltage which is compared with the load voltage of the transducer U in a differential amplifier AE1, forming part of a first feedback loop, to adjust a voltage generator GT controlling the output voltage of the main amplifier AM so as to eliminate any voltage drop across the series resistor R as long as the input signal is absent or has an instantaneous magnitude equal to its mean value.

Abstract: An electronic organ in which a manually adjustable potentiometer varies the control voltage supplied to a voltage controlled amplifier interposed between a source of tone signals and an organ output circuit with the potentiometer being connected to the amplifier by a circuit which eliminates scratching and discontinuity in the potentiometer output. The amplifier can be bypassed by circuitry for supplying lower frequency bass signals to the amplifier output under conditions of high attenuation of the incoming signal in the amplifier.