158results about "Control circuit for distortion reduction" patented technology

A gain boost circuit and methodology are described for providing improved gain boosting with tuned amplifier circuits, such as differential low noise amplifier circuits having output resonant tank circuits. By selectively controlling the current source for a negative transconductance stage coupled between the differential amplifier output and the output resonant tank circuits, the amplifier gain may be adjusted to compensate for temperature variations. In addition, the amplifier gain boost may be selectively added, removed or even incrementally adjusted by using a current source control circuit in the negative transconductance stage to adjust the negative transconductance value generated by the negative transconductance stage.

The present invention reduces automatic gain control (AGC) transients using first and second AGC processing branches to receive a signal. A gain is selectively adjusted (if desired) in the one of the AGC processing branches during a first time period. However, a gain is not adjusted in the other AGC processing branch during that first time period. The signals generated by the first and second AGC processing branches are then diversity processed to generate a received signal. The diversity processing effectively reduces the effect of any AGC transient.

In receiver systems for cellular phones using the W-CDMA method, the change in DC voltage occurring when the gain of a programmable gain amplifier (PGA circuit) is switched to adjust the gain for a received signal, can be suppressed. A sample-and-hold circuit is installed containing a “sample” mode for directly outputting a signal from the PGA section and also containing a “hold” mode for outputting the electric charge of a specified voltage stored in a capacitor. This sample-and-hold circuit normally operates in “sample” mode so the output signal from the PGA section is directly output, but is operated in “hold” mode at the gain switching timing of the PGA circuit, so that the electric charge of the specified voltage stored in the capacitor is output for a specified length of time (equal to the time required for the DC voltage change to converge to a stable level).

A signal processing system (100) comprises an input terminal (102), and a main path having a main filter input gain unit (126) coupled to said input terminal (102), a main filter (132) and an output gain unit (138). An auxiliary path includes an auxiliary filter input gain unit (106) coupled to the input terminal (102), an auxiliary filter (112) and an auxiliary filter output gain unit (118). An adder (144) is coupled to the output gain units (118, 138) for generating an output signal to an output terminal (148). The gains of the gain units are adjusted by a control unit (18) responsive to a detecting signal from a detector (160).

The present invention provides a semiconductor integrated circuit for communication (radio frequency IC) capable of detecting and correcting variations in an amplitude loop band of a transmission circuit having a phase control loop and an amplitude control loop without using an external measuring apparatus. In a semiconductor integrated circuit for communication (radio frequency IC) including a transmission circuit having a phase control loop for controlling the phase of a carrier wave and an amplitude control loop for controlling the amplitude of a transmission output signal, a calibration circuit for detecting variations in a loop gain of the amplitude control loop and correcting the loop band is provided. The calibration circuit detects variations in a loop gain by comparing a feedback signal with an output signal of a modulation circuit while changing electric parameters of any of circuits on the amplitude control loop step by step, and corrects the loop band by changing characteristics of any of the circuits on the amplitude control loop in accordance with the detected variations.

An output power limiter system (PLS) for audio amplifiers may be designed as a feedback control system for protection of the load and / or quality of the audio experience. The PLS may use comparator to sense the output current, compare it to a specified threshold, and assert a signal when the output current reaches and exceeds the specified threshold. The output signal from the comparator may enable a counter that is clocked with a high frequency clock to begin counting to measure the pulse-width of the comparator output. The output of the counter may be averaged through a fast attack and slow release infinite impulse response (IIR) filter having programmable settings to generate a rate of attenuation or rate of release that adjusts a gain correction in terms of decibels (dB). The output of the IIR filter may then be used for attenuating the output current.

The invention discloses an automatic gain control circuit of an audio power amplifier, which comprises a fully differential operational amplifier and an automatic gain control circuit, wherein the in-phase and anti-phase input ends of the amplifier are provided with divider resistors respectively; feedback resistors are arranged between the in-phase input end and an output end as well as between the in-phase input end and the output end respectively; a biasing circuit is connected the fully differential operational amplifier; the input end of the control circuit is connected with the output end of the fully differential operational amplifier; a reference voltage circuit is connected with the control circuit; and the output end of the control circuit is connected with an adjustable resistor at the input end of the fully differential operational amplifier. In the invention, an output signal is compared with a reference voltage to obtain a digital signal, and the digital signal is used for controlling the front resistance value of the input end of the amplifier, so that a fixed gain can be kept for amplifying an audio signal during inputting of a small signal, closed-loop gain in the circuit is reduced during inputting of a large audio signal, and high linearity and low harmonic distortion of an output audio signal are ensured.

A high dynamic range amplifier with variable gain comprises an amplifier module, a control unit and a circuit for regulating output current capacity. The amplifier module is used for amplifying an input signal and consists of a plurality of amplifier units which are coupled with each other in parallel and have different gain values; the control unit is used for enabling at least one amplifier unit according to a gain control signal, and at least one enabled amplifier unit is used for responding to the input signal to output a current signal; the circuit for regulating output current capacity is used for receiving a current signal output by at least one enabled amplifier unit and regulating the strength of the current signal under the control of the control unit to output an output signal correspondingly, wherein, each of the amplifier units is coupled with the circuit for regulating output current capacity in series.

The invention provides an adjustable gain low noise amplifier, wherein a predistorter compares gain control voltage Vc with reference voltage Vref, converts into first bias current Ibias, and the first bias current Ibias is supplied for an adjustable gain module; a minimum gain module provides minimum gain control and inputs second bias current Ibias2 for adjusting the gain; and the output of theadjustable gain module and the output of the minimum gain module are combined as the radio-frequency output of the adjustable gain low noise amplifier. Because the gain of the adjustable gain module is controlled by a bias signal after predistortion, the gain of the adjustable low noise amplifier near the reference voltage and the gain control voltage are in logarithm linear relation, and simultaneously the maximum gain and the minimum gain of the adjustable gain low noise amplifier are accurately controlled by arranging the minimum gain module. The adoption of bias current for controlling the gain has the advantage that when the signal is larger, the working current of the amplifier is greatly reduced, so that the power consumption is saved.

The invention relates to a protective device and a method for power amplification of a UHF broad frequency band transmitter, comprising an input overpower protecting unit, an output overpower protecting and output standing wave ratio protecting unit, a power amplifier, an output sampling unit, a power amplification control unit, temperature detection, power supply detection, and a control method; a radio-frequency signal enters the power amplifier by passing through the input overpower protecting unit and the output overpower protecting and output standing wave ratio protecting unit, and finally passes through the output sampling unit; the power amplification control unit is a control center and used for loading a control program so as to obtain various data of power amplification working condition and setting and controlling the input overpower protecting unit, the output overpower protecting and output standing wave ratio protecting unit and the power supply detection. The beneficial effect of the invention is that: by effectively integrating a plurality of units together, the power amplification of the UHF broad frequency band transmitter can be effectively and reliably protected in an all-around manner, and the working reliability and the practical service life of the transmitter are improved.

A gain boost circuit and methodology are described for providing improved gain boosting with tuned amplifier circuits, such as differential low noise amplifier circuits having output resonant tank circuits. By selectively controlling the current source for a negative transconductance stage coupled between the differential amplifier output and the output resonant tank circuits, the amplifier gain may be adjusted to compensate for temperature variations. In addition, the amplifier gain boost may be selectively added, removed or even incrementally adjusted by using a current source control circuit in the negative transconductance stage to adjust the negative transconductance value generated by the negative transconductance stage.

This variable gain amplifier is provided with an operational amplifier. The non-inversion input terminal of the operational amplifier is connected to a reference potential. A feedback resistor is connected between the output terminal and inversion input terminal of the operational amplifier. An input resistor is inserted between the inversion input terminal of the operational amplifier and the input terminal of the variable gain amplifier circuit. An adjustment resistor is connected between the inversion input terminal of the operational amplifier and the reference potential. The resistance value of the adjustment resistor is controlled in such a way as to maintain constant against the resistance value change a combined resistance value in its parallel connection with the input resistor when changing the resistance value of the input resistor.

An amplifier may include two or more pulse-width modulators controlling respective sets of switches to produce an amplified version of a source signal. A positive DC-offset based on the source signal may be applied to the pulse-width modulator controlling one respective set of switches, and an equal value negative DC-offset may be applied to the pulse-width modulator controlling the other respective set of switches, to provide an effective offset between the respective points in time of the rising / falling edges of the different pulse-width modulated control signals. The addition of alternating positive and negative DC-offset values doesn't affect the output load, and doesn't degrade the signal. The DC-offsets may be added at a frequency selected to be beyond the signal baseband, and the value of the small input signal level may be determined using an RMS level comparator or similar measurement technique.

A feedback circuit for amplification of the output signal of an analog front end and suppression of its DC and low frequency components comprises a variable gain amplification unit (2) controlled by a gain control signal and a reverse path unit (6) comprising a filter unit (8) with variable time constant. A control unit (13) produces the gain control signal as well as a reverse path control signal (S) which causes adaptation of variable resistances (12) and capacitances (10) in such a way that the time constant of the filter unit (8) varies essentially proportionally with the gain of the variable amplifier unit (2). Thereby the gain of the feedback circuit as a function of the frequency retains its shape with varying gain. As the reverse path control signal (S) can be produced from different inputs selectable by selectors (20a, 20b) in the control unit (13) and due to the adaptability of the reverse path unit (6) and other features the analog base band unit is suited for the processing of signals of various types, e.g. signals pertaining to GPS and mobile telecommunication systems.

A bias circuit 22 in a power amplifier 1 is provided with a VBE-controlled voltage source circuit 20 and a Nagata current mirror circuit 21. The Nagata current mirror circuit 21 includes a transistor Tr5 and a transistor Tr6. The transistor Tr5 has its emitter grounded, its base connected to a control input terminal 17 via a resistor R3, and its collector connected to that base via a resistor R4. The transistor Tr6 has its emitter grounded, its base connected to the collector of the transistor Tr5, and its collector connected to the base of the transistor Tr3. The arrangement is capable of compensating both the temperature characteristics of the gain of the power amplifier 1 and the control input voltage characteristics of the gain of the power amplifier 1. In other words, the arrangement is capable of reducing the temperature dependence and control input voltage dependence of the gain of the power amplifier 1.

The invention discloses an adjustable grain low noise amplifier which is a cascode. The adjustable grain low noise amplifier comprises a grain adjusting control circuit, a load circuit, a current guiding circuit and an input circuit, wherein the grain adjusting control circuit is used for receiving a grain adjusting voltage and further generating a resistance value adjusting signal and a current guiding control signal; the load circuit comprises a plurality of variable resistors and is used for adjusting the resistance values of the plurality of the variable resistors according to the resistance values; the current guiding circuit is connected to the load circuit through a plurality of current paths and is used for adjusting the current ratios among the plurality of current paths according to the current guiding control signal and the current guiding circuit is provided with a differential signal output end; and the input circuit is connected to the current guiding circuit, wherein the input circuit is provided with a differential signal input end. The amplifier can provide low noise index during low grain and provide wider grain adjusting range, and further achieve lower power loss, smaller layout area, lower linearity requirement and other effects.

A gain boost circuit and methodology are described for providing improved gain boosting with tuned amplifier circuits, such as differential low noise amplifier circuits having output resonant tank circuits. By selectively controlling the current source for a negative transconductance stage coupled between the differential amplifier output and the output resonant tank circuits, the amplifier gain may be adjusted to compensate for temperature variations. In addition, the amplifier gain boost may be selectively added, removed or even incrementally adjusted by using a current source control circuit in the negative transconductance stage to adjust the negative transconductance value generated by the negative transconductance stage.

An automatic gain control circuit for controlling the gain of a variable gain amplifier block includes a count control signal generating block, an up-down counter, a gain control signal generating block, and a downcount clock signal generating block. The up-down counter upcounts an upcount clock signal or downcounts a downcount clock signal according to a count control signal generated by the count control signal generating block. The gain control signal generating block generates a gain control signal corresponding to a count value of the up-down counter. The downcount clock signal generating block generates a downcount clock signal whose frequency corresponds to the count value of the up-down counter. Correspondingly, an automatic gain adjustable circuit with more excellent in audio can be realized without using integral circuit of the capacitor.

The invention provides a gain compensation device over temperature and a method thereof. the gain compensation device for adjusting gain of an amplifier over temperature is disclosed. The gain of the amplifier is controlled by signals on a gain control end of the amplifier. The gain compensation device comprises a temperature compensation generator, an adder, and a temperature sensor. The temperature compensation generator is for generating an additional gain parameter according to a reference temperature, a current temperature, and a temperature coefficient. The adder comprises a first input end, coupled to the temperature compensation generator for receiving the additional gain parameter, a second input end for receiving a default gain parameter, and an output end coupled to the gain control end of the amplifier for outputting sum of the additional gain parameter and the default gain parameter. The temperature sensor is for providing the current temperature. The gain compensation device could make the actual gain keep constant owing to temperature change according to gain of temperature adjusting gain amplifier so as to provide great convenience.

A novel method of enhancing power amplifier linearity is disclosed. The invention is for use within a transceiver system and provides a method in the digital domain for predistorting a digital modulated signal to compensate for the non-linearity properties of the power amplifier and other components within the transmitter system. The RF output signal of the transmitter circuit is sampled and the corresponding amplitude and phase are detected using a receiver circuit. In dependence upon the amplitude and phase information, a look-up table is indexed to select the predistortion data and predistortion of the digital modulated signal occurs within the predistortion circuit.

Circuits and methods for controlling power amplifiers. In some embodiments, a power amplification system can include a first amplification stage configured to operate with a first bias signal, and a second amplification stage configured operate with a second bias signal. The power amplification system can further include a control circuit coupled to the first amplification stage and the second amplification stage. The control circuit can be configured to generate the first bias signal based on the second bias signal. Such a first bias signal can result in the first stage having a gain profile that compensates for either or both of a gain expansion and gain compression of the second amplification stage.

A sound volume adjuster includes: a storage which stores a first value of a volume setting value and an allowable maximum change amount; a receiver which receives a change request indicating a second value of the volume setting value; a determiner which, when a change amount of the volume setting value between the first value and the second value exceeds the allowable maximum change amount, determines that the change request is an excessive request; and an adjuster which, when the determiner determines that the change request is the excessive request: changes the first value stored in the storage by a change amount which is equal to or smaller than the allowable maximum change amount to set a third value of the volume setting value; and adjusts a sound volume by the third value.

The invention discloses a compensation device for a power amplifier and a related method. The method for determining a pre-distortion value of the power amplifier comprises the following steps of: providing a first power input signal to make the power amplifier generate a first power output signal; receiving a first receiving signal which is acquired according to the first power output signal; detecting the predetermined gain of the power amplifier by using the first power input signal and the first receiving signal; providing a second power input signal to make the power amplifier generate a second power output signal; receiving a second receiving signal which is acquired according to the second power output signal; and determining a pre-distortion amplitude value and a pre-distortion phase value of the power amplifier by using the predetermined gain, the second power input signal and the second receiving signal.

There is provided a variable gain amplifier that is implemented with a CMOS device and has wide band variation and wide bandwidth by a predetermined exponential function. A variable gain amplifier having wide gain variation and wide bandwidth according to an aspect of the invention may include: a differential amplification section differentially amplifying an input signal according to a gain adjustment signal; and a gain adjustment section supplying the gain adjustment signal on the basis of an approximated exponential function determined according to a predetermined bias current, and adjusting a gain of the differential amplification section.

The direct conversion receiving apparatus has a gain control amplifier for variably amplifying a base band signal based on a gain switching control signal. A high pass filter has a first circuit including capacitors connected in parallel that are inserted in a path connecting an input terminal to an output terminal and switching effective total capacitance of the capacitors based on a first time constant switching control signal, and a second circuit including a resistor for providing a predetermined direct current voltage to the output terminal and switching the effective resistance value of the resistor based on a second time constant switching control signal. A control circuit outputs the gain switching control signal, and the first and second time constant switching control signals according to the change of the gain control of said gain control amplifier.

An adaptive current control circuit for reduced power consumption and minimized gain shift in a variable gain amplifier. An automatic gain control circuit provides gain control voltages in response to a gain control signal. The gain control voltages are used by the variable gain amplifier to set the gain of the output signal for wireless transmit operations. The adaptive current control circuit receives the same gain control voltages for reducing current to the variable gain amplifier during low gain operation, while providing higher currents during high gain operation. The current that is provided is a hybrid mix of proportional to absolute temperature (PTAT) current and complementary to absolute temperature (CTAT) current for minimizing temperature effects on the gain. The ratio of PTAT current and CTAT current is adjustable for specific temperature ranges to further minimize temperature effects on the gain.

The invention discloses an adjustable gain audio power amplification circuit which comprises an input unit, an audio amplification unit, a gain adjusting unit, a control unit, a comparison unit and an output unit, wherein the audio amplification unit is connected with the input unit, the gain adjusting unit is connected with the audio amplification unit, the control unit is connected with the gain adjusting unit, the comparison unit is connected between the gain adjusting unit and the control unit, and the output unit is connected with the audio amplification unit; the comparison unit compares an output signal of the output unit with a common-mode reference voltage and outputs a gain adjusting control signal to the control unit, and the gain adjusting control signal is inversed when the output signal of the output unit is equal to the common-mode reference voltage; when detecting that the gain adjusting control signal is inversed, the control unit transmits a received gain adjusting signal to the gain adjusting unit; then, the gain adjusting unit controls the gain of the adjustable gain audio power amplification circuit according to the received gain adjusting signal. The adjustable gain audio power amplification circuit disclosed by the invention is simple in structure, and cracking noise generated by gain adjusting is avoided.

A programmable gain amplifier is provided, belonging to the technique field of amplifying circuit, comprising a full balanced differential amplifier module, a decoder module and a resistance switch array module. The maximum gain of the amplifier is determined by resistance ratio of inverse feedback resistive divider; attenuation of input signal is attenuated by the resistance switch array module controlled by the decoding result of the decoder module, to accomplish gain programmable property of the amplifier. The resistance switch array model is two symmetrical resistance attenuation networks comprising analog switch. The input resistance thereof is constant, to guarantee load effect constant to front stage. The amplifier has the following advantage: simple structure, stable band width, and constant input resistance. The invention forms load effect constant to front stage, so that no buffer circuit is required to separate the amplifier to the front stage.

A switching audio amplifier may include a modulation enhancement feature, in which the pulse-width modulated (PWM) signals driving the output stage are reduced or increased by identical step sizes to create an auxiliary PWM scheme representative of an idle (low-power) state of the input signal. The PWM signals, provided to a full-bridge power stage circuit for example, may be thereby reduced to another state to reduce power dissipation in a switch-mode power supply. By incrementally adjusting the PWM duty-cycle identically in all PWM signals to a value less than (or up to) 50%, the amount of current dissipated in the output load may be effectively controlled. The PWM pulses may be adjusted up or down, while checking for saturation corresponding to both minimum and maximum pulse-widths. A dampener circuit may be used to set the time between incremental adjustments, to further reduce audible pops and clicks.