Abstract: A method of measuring the response of an electronic device to a high frequency input signal is performed with an analyzer (1).

Abstract: The present invention provides radio frequency (RF) power controllers that regulate the power output signal of an RF power amplifier using a control signal. The RF power controller includes a power control amplifier that measures the difference between a feedback signal and a power control input signal to supply the control signal to the RF power amplifier. The output power signal is amplitude modulated for a period of time during an enable mode. During the amplitude modulation period, the RF power controller opens the power control loop and maintains a substantially constant output voltage to the RF power amplifier using a second amplifier and a capacitor coupled to power control amplifier. The capacitor is decoupled from the power control amplifier during the amplitude modulation period, and the second amplifier supplies the output voltage of the RF power controller based upon the stored voltage on the capacitor.

Abstract: A pad circuit and operating method for automatically adjusting gains is disclosed, wherein the pad circuit is embedded in an integrated circuit chip that further includes a core logic circuit therein. The pad circuit includes an input/output pin, a gain-adjustable output buffer, an input buffer and a signal feature detector. The method includes the steps as follows. A test signal is firstly issued from the core logic circuit to the gain-adjustable output buffer, while the test signal is then manipulated and outputted to an external device via the input/output pin. Next, a feedback test signal is fed into the input buffer from the external device, while a test result is realized according to a waveform feature of the feedback test signal. Finally, the gain of the gain-adjustable output buffer is adjusted according to the obtained test result.

Abstract: The masking-effect of loud audio passages is utilized to reduce the audibility of the fan noise from a cooling fan in an audio system. A power monitor determines an output power of an audio amplifier and generates a power signal proportional to the output power. A switchable cooling fan is positioned to provide a cooling flow of air within the audio system when the cooling fan is turned on. A fan control is coupled to the power monitor and the switchable cooling fan. The fan control compares the power signal with a predetermined threshold and turns on the switchable cooling fan in response to the comparison indicating that reproduction of the amplified audio signals is at an output power level that will substantially mask audible noise created by the switchable cooling fan.

Abstract: A method and circuit control a quiescent current of an amplifier including a preamplifier, error amplifiers, and output devices driven by the error amplifiers, the error amplifiers having an input-referred offset voltage. The method includes (a) applying a calibration voltage to an input of the error amplifiers, (b) calibrating a quiescent current of the output devices by changing the calibration voltage so that the calibrated quiescent current has a predetermined current value, the calibration voltage corresponding to the calibrated quiescent current being set as a correction voltage, and (c) operating the amplifier with the correction voltage applied to the input of the error amplifiers. The circuit includes a correction voltage generator supplying a correction voltage to the error amplifier input, a quiescent current detector detecting the quiescent current, and a calibration circuit adjusting the correction voltage so that the quiescent current is calibrated to a predetermined current value.

Abstract: A predistortion linearizer of a power amplifier capable of improving the nonlinearity of the power amplifier by compensating changes in the power amplifier's nonlinear characteristics according to the lapse of time or an external environment and easily implementing the reverse characteristics of the power amplifier's nonlinear characteristics is disclosed. The predistortion linearizer of the power amplifier as disclosed includes a control unit for controlling a gain and phase of an input signal so that they are the reverse of the power amplifier's nonlinear characteristics, and a unit for compensating changes in the power amplifier's distortion characteristics according to the lapse of time or an external environment, upon receipt of the output of the control unit.

Abstract: A method of setting up a linearizing circuit such as a linear power amplifier is described. According to the method, an input signal is supplied at a low, starting power level and is lowly increased during a set-up until it attains an operational level for normal use. The advantage of this is that pilot tone used in the linearizing circuit can be readily detected during set-up because its amplitude is above that of the low, starting power level of the input signal. A feed-forward linearizing system and a transmission system utilizing the technique are described.

Abstract: Circuits and methods for calibrating offset error in a differential amplifier in an efficient and reliable way are described. A final calibrated state for the differential amplifier is obtained in accordance with a nonlinear search that requires significantly fewer test stages to complete than linear search methods. As a result, longer test periods may be used with the invention without adversely affecting the overall length of the calibration process. Because circuit conditions near the calibration point cause internal test signals to switch more slowly from one state to another, lengthening the test period time may allow more time for the internal test signals to reach their final values and, thereby, improve calibration accuracy.

Abstract: In the mobile communication, a distortion compensation amplifying apparatus is provided.

Abstract: A method of measuring the response of an electronic device to a high frequency input signal is performed with an analyzer (1).

Abstract: The calibration circuit is used with a differential input, monolithic integrated circuit preamplifier in a sensor system. The calibration circuit tests the integrity of the sensor, the preamplifier, and the wiring in the sensor system. The calibration circuit includes first and second calibration capacitors having different capacitances connected to the preamplifier input leads. A calibration signal source is connected between the capacitors. The capacitors are preferably implemented on the same integrated circuit as the preamplifier. In operation, a calibration signal of known amplitude is applied to the calibration circuit and the level at the preamplifier output is determined. The level at the preamplifier output indicates certain conditions relating to the integrity of the sensor and its wiring, for example, an open circuit condition or a short circuit condition.

Abstract: A control unit and two negative feedback branches limit the amplitudes of the output signal of an inverting differential amplifier. Each feedback branch includes a threshold value switch including a transistor as well as an adjustable current source and a resistor forming a voltage divider between a supply voltage and the amplifier output. The voltage divider output is connected to the transistor's base. The transistor selectively connects or disconnects the input of the amplifier with either the supply voltage or the amplifier output. The control unit controls the two current sources based on external programming commands, to establish two adjustable threshold values within which the negative and positive amplitudes of the output signal are limited, symmetrically or independently, in a hard or soft clipping manner. Even with small supply voltages, the limited output will not overdrive subsequent amplifier input stages and will not superimpose harmonics on the useful signal.

Abstract: Disclosed is an apparatus and method for modeling and estimating the characteristics of a power amplifier. A predistortion module generates a predistorted signal in response to a predistortion function and an input signal. A power amplifier receives the predistorted signal and generates an output signal. A polynomial module generates coefficients of a complex polynomial of order p (p is an integer greater than one) in response to the predistorted signal and the output signal. In particular, the complex polynomial is inplemented with both even and odd terms, thereby improving the ability to accurately model the power amplifier.

Abstract: An injection current test circuit for an amplifier (24) includes a test current input pad (16). One (14) of a plurality of current mirrors (12) is connected to the test current input pad (16). A switch (20) is connected to a second (18) of the plurality of current mirrors (12) and connected to the amplifier (24). A test current output pad (22) is connected to the switch (20).

Abstract: Disclosed is an apparatus and method for modeling and estimating the characteristics of a power amplifier. A predistortion module generates a predistorted signal in response to a predistortion function and an input signal. A power amplifier receives the predistorted signal and generates an output signal. A polynomial module generates coefficients of a complex polynomial of order p (p is an integer greater than one) in response to the predistorted signal and the output signal. In particular, the complex polynomial is implemented with both even and odd terms, thereby improving the ability to accurately model the power amplifier.

Abstract: Disclosed is an apparatus and method for iteratively calculating the predistortion function from a power amplifier when the inverse to the power amplifier characterization does not exist analytically. A predistortion module generates a predistorted signal in response to an input signal and a predistortion function received from a predistortion function calculating module. The predistortion function calculating module generates the predistortion function in response to given amplifier characteristics. In particular, the predistortion function calculating module uses a magnitude of the input signal at a given time to estimate the predistorted signal at that given time in order to calculate the predistortion function. Optionally, subsequent iterations based on the magnitude of the estimate occur until a desired accuracy of the predistorted signal approximation and of the predistortion function is achieved.

Abstract: Disclosed is an apparatus and method for iteratively calculating the predistortion function from a power amplifier when the inverse to the power amplifier characterization does not exist analytically. A predistortion module generates a predistorted signal in response to an input signal and a predistortion function received from a predistortion function calculating module. The predistortion function calculating module generates the predistortion function in response to given amplifier characteristics. In particular, the predistortion function calculating module uses a magnitude of the input signal at a given time to estimate the predistorted signal at that given time in order to calculate the predistortion function. Optionally, subsequent iterations based on the magnitude of the estimate occur until a desired accuracy of the predistorted signal approximation and of the predistortion function is achieved.

Abstract: A device for compensating for the nonlinearity of a power amplifier which has a simple configuration and can precisely linearize the transfer characteristics of the power amplifier by predistorting an input signal of the power amplifier. The nonlinearity compensation device of the present invention converts an RF input signal into an IF band rather than a baseband and predistorts the RF input signal in digital domain, and thus any modulation or demodulation process is obviated and the simultaneous processing of signals in multiple channels is facilitated. A first downconverter receives the RF input signal and converts the frequency band of the signal into the IF band to output an IF input signal. A predistortion unit receives and predistorts the IF input signal to compensate for the nonlinearity, and outputs an IF predistorted signal. An upconverter converts the frequency band of the IF predistorted signal into the RF band to provide such a signal to the amplifier.

Abstract: This invention relates to an amplifier having digital micro-processor control apparatus and, in particular, to a high frequency power amplifier that includes a micro-processor control system to accurately regulate the operating point of the various amplifying elements in the high frequency power amplifier. The basic amplifier circuitry consists of a micro-controller, a variable voltage attenuator (VVA), a digital to analogue converter and an EEPROM. The EEPROM provides a lookup table which is read by the micro-controller, which then writes to the digital to analogue converter to set the control voltage to the variable voltage attenuator.

Abstract: A method and apparatus for auto-calibrating an electronic device without interrupting normal operation of the device. An electronic device configured as a high voltage difference amplifier is disclosed having a calibration circuit which couples a calibration excitation signal to a common-mode signal path of the difference amplifier. The difference amplifier includes a variable transfer function circuit which may be used to adjust the common-mode rejection of the difference amplifier. The calibration excitation signal may be a random, pseudo-random, out-of-band, or other frequency shaped signal generated in reference to a clock signal. A calibration error signal is detected from an output signal. The variable transfer function circuit can be adjusted in response to the detected error signal to reduce the calibration error signal. As a result, common-mode rejection errors of the difference amplifier may be reduced while the difference amplifier is coupled to an input signal source.

Abstract: A wideband predistortion system compensates for a nonlinear amplifier's frequency and time dependent AM—AM and AM-PM distortion characteristics. The system comprises a data structure in which each element stores a set of compensation parameters (preferably including FIR filter coefficients) for predistorting the wideband input transmission signal. The parameter sets are preferably indexed within the data structure according to multiple signal characteristics, such as instantaneous amplitude and integrated signal envelope, each of which corresponds to a respective dimension of the data structure. To predistort the input transmission signal, an addressing circuit digitally generates a set of data structure indices from the input transmission signal, and the indexed set of compensation parameters is loaded into a compensation circuit which digitally predistorts the input transmission signal.

Abstract: Disclosed is an apparatus and method for calculating a predistortion function from power amplifier characteristics. A predistortion module generates a predistorted signal in response to an input signal and predistortion coefficients received from a predistortion function calculating module. The predistortion function calculating module generates the predistortion coefficients in response to the given amplifier characteristics. Polynomial fitting is used to obtain the predistortion coefficients. In particular, the input signal is represented by single or multiple sectors having multiple points and then predistortion coefficients are calculated for each sector.

Abstract: A wideband predistortion system compensates for a nonlinear amplifier's frequency and time dependent AM—AM and AM-PM distortion characteristics. The system comprises a data structure in which each element stores a set of compensation parameters (preferably including FIR filter coefficients) for predistorting the wideband input transmission signal. The parameter sets are preferably indexed within the data structure according to multiple signal characteristics, such as instantaneous amplitude and integrated signal envelope, each of which corresponds to a respective dimension of the data structure. To predistort the input transmission signal, an addressing circuit digitally generates a set of data structure indices from the input transmission signal, and the indexed set of compensation parameters is loaded into a compensation circuit which digitally predistorts the input transmission signal.

Abstract: Provided is a system and method for concurrently adjusting parameters of a system incorporating separate devices. In a preferred embodiment, a series of amplifiers used in an instrumentation system are able to be adjusted and calibrated concurrently via a simple operation of an unskilled operator. One option provides for this adjustment to occur remotely from the devices.

Abstract: A method of setting up a linearizing circuit such as a linear power amplifier is described. According to the method, an input signal is supplied at a low, starting power level and is lowly increased during a set-up until it attains an operational level for normal use. The advantage of this is that pilot tone used in the linearizing circuit can be readily detected during set-up because its amplitude is above that of the low, starting power level of the input signal. A feed-forward linearizing system and a transmission system utilizing the technique are described.

Abstract: Three kinds of shrink factors, 1 time, 0.5 time, and 0.25 time, are prepared and three sets of operational amplifier layout information are also prepared as a library in correspondence with the three kinds of shrink factors. At each shrink factor, the bias voltage is varied between upper and lower limits to vary the bias current.

Abstract: A cartesian amplifier system for pre-distorting a signal to be amplified to take account of non-linearities and other non-ideal characteristics of the amplifier itself. A signal to be amplified is divided into quadrature and in-phase signal components in a digital signal processor 1. The processor 1 also pre-distorts the resolved quadrature and in-phase components using various pre-distortion factors. These pre-distortion factors are derived on the basis of a feedback signal from a measurement of the output signal power from the amplifier and on the basis of the signal levels of the pre-distorted resolved components themselves. These pre-distortion factors are constantly updated, thus taking into account any shifts in the non-ideal characteristics of the amplifier.

Abstract: An operational amplifier is trimmed electrically using non-volatile fuses. The non-volatile fuses may be programmed electrically without destroying any passivation layers or other devices on the electronic component. In the case of an integrated circuit analog component, the trimming may be performed either at the wafer level or at the packaging level. The trimming may be performed specifically to adjust the quiescent current or offset voltage of the operational amplifier.

Abstract: An apparatus for conditioning an electronic signal that includes a number of signal amplifiers sequentially arranged from a first amplifier to a final amplifier. There is also a microcontroller/microcomputer. A balance circuit is interposed between the first amplifier and the microcontroller/microcomputer, and a calibration step circuit is interposed between the microcontroller/microcomputer and a second amplifier. A digital to analog converter (DAC) is interposed between the microcontroller/microcomputer and each of the amplifiers.

Abstract: The invention relates to a method of digitally linearizing an amplifier having non-linearity, the method being of the type comprising: a prior stage in which correction parameters for correcting said non-linearity are determined, and a linear amplification stage performed by applying predistortion followed by amplification. In the invention, stage in which the correction parameters are determined comprises the following steps: acquiring said amplified test signal in the form of samples in baseband; defining a modelled amplifier, by computing parameters of a predetermined amplifier model on the basis of said samples of the amplified test signal; and computing said correction parameters on the basis of said modelled amplifier so that they make it possible to linearize said modelled amplifier. The invention also relates to a corresponding system for digitally linearizing an amplifier.

Abstract: A wideband predistortion system compensates for a nonlinear amplifier's frequency and time dependent AM-AM and AM-PM distortion characteristics. The system comprises a data structure in which each element stores a set of compensation parameters (preferably including FIR filter coefficients) for predistorting the wideband input transmission signal. The parameter sets arc preferably indexed within the data structure according to multiple signal characteristics, such as instantaneous amplitude and integrated signal envelope, each of which corresponds to a respective dimension of the data structure. To predistort the input transmission signal, an addressing circuit digitally generates a set of data structure indices from the input transmission signal, and the indexed set of compensation parameters is loaded into a compensation circuit which digitally predistorts the input transmission signal.

Abstract: A process and product providing a High Efficiency Microwave Power Amplifier (HEMPA) which propagates S-Band microwave frequency square waves; utilizing a program simulating FETs at high DC-to-RF efficiencies, which analyses linear elements of selected FETs in a frequency domain, and non-linear elements of the FETs in a time domain, and converts the time domain values into the frequency domain, and performs DC and S-parameter simulated measurements based on predefined data for each FET. Individual FET parameters are extracted and isolated by converting the S-parameters to admittance or impedance parameters to derive FET models for each FET, which the program uses to provide a final output of a HEMPA circuit based on iterative simulations of an amplification circuit utilizing microwave topology and frequencies. Iterative simulations of the amplification circuit analyze output values of a plurality of cascaded stages of the FETs, which are arranged in a push-pull configuration.

Abstract: A method of deriving a pre-distorter for a corresponding non-linear amplifier is disclosed. The first step of the method is to form the pre-distorter's topology. This is done by first determining a corresponding inverse topology to the non-linear amplifier's topology. The non-linear amplifier has a topology comprising filter and non-linear amplifier elements. The inverse topology comprises corresponding inverse filter and amplifier elements to the amplifier's filter and non-linear amplifier elements. Then, those of the inverse filter and amplifier elements for which compensation with the pre-distorter is desired are selected. Any of the inverse filter and amplifier elements that were not selected are then removed from the inverse topology to form the pre-distorter's topology. Thus, the pre-distorter's topology comprises the selected inverse filter and amplifier elements.

Abstract: A wideband predistortion system compensates for a nonlinear amplifier's frequency and time dependent AM-AM and AM-PM distortion characteristics. The system comprises a data structure in which each element stores a set of compensation parameters (preferably including FIR filter coefficients) for predistorting the wideband input transmission signal. The parameter sets are preferably indexed within the data structure according to multiple signal characteristics, such as instantaneous amplitude and integrated signal envelope, each of which corresponds to a respective dimension of the data structure. To predistort the input transmission signal, an addressing circuit digitally generates a set of data structure indices from the input transmission signal, and the indexed set of compensation parameters is loaded into a compensation circuit which digitally predistorts the input transmission signal.

Abstract: An analog-to-digital converter comprising: an amplifier group for comparing a plurality of reference voltages with an analog voltage of an input analog signal, the amplifier group being composed of a plurality of individual amplifiers, an encoder for generating a digital code corresponding to the results of the comparison made in each of the amplifiers of the amplifier group, and a comparison-result output means which, when executing the test of the amplifier group, inputs all the results of the comparison made in each of the amplifiers together, and sequentially outputs these comparison results per one bit for each time, wherein the comparison-result output means may be a shift register that first inputs results of the comparison made in the amplifier group all at once, and thereafter outputs the thus input results of the comparison made in a plurality of amplifiers per one bit for each time in synchronization with the clock signals.

Abstract: A wideband predistortion system compensates for a nonlinear amplifier's frequency and time dependent AM-AM and AM-PM distortion characteristics. The system comprises a data structure in which each element stores a set of compensation parameters (preferably including FIR filter coefficients) for predistorting the wideband input transmission signal. The parameter sets are preferably indexed within the data structure according to multiple signal characteristics, such as instantaneous amplitude and integrated signal envelope, each of which corresponds to a respective dimension of the data structure. To predistort the input transmission signal, an addressing circuit digitally generates a set of data structure indices from the input transmission signal, and the indexed set of compensation parameters is loaded into a compensation circuit which digitally predistorts the input transmission signal.

Abstract: A system and method for employing a training scheme to a linear amplifier system having a modulator component for modulation of a supply power of an RF power amplifier. A supply modulator is set at a maximum or peak supply voltage of the RF power amplifier that corresponds to a maximum saturation point of the RF power amplifier. A training mode is entered wherein an input signal is provided and a phase adjustment and an attenuation level for the input signal to the RF power amplifier is determined. The phase adjustment and attenuation level is employed in normal operation. A relationship between the maximum clip level and maximum supply voltage and the instantaneous voltage level of the supply that will be utilized to modulate the reference signal is employed to determine the attenuation level.

Abstract: A wideband predistortion system compensates for a nonlinear amplifier's frequency and time dependent AM-AM and AM-PM distortion characteristics. The system comprises a data structure in which each element stores a set of compensation parameters (preferably including FIR filter coefficients) for predistorting the wideband input transmission signal. The parameter sets are preferably indexed within the data structure according to multiple signal characteristics, such as instantaneous amplitude and integrated signal envelope, each of which corresponds to a respective dimension of the data structure. To predistort the input transmission signal, an addressing circuit digitally generates a set of data structure indices from the input transmission signal, and the indexed set of compensation parameters is loaded into a compensation circuit which digitally predistorts the input transmission signal.

Abstract: A method is described for estimating at least the inverse amplitude characteristic in a high-power amplifier for transmission systems, wherein the estimation is carried out by estimation means receiving the signal samples, possibly demodulated, as inputs present at the input and at the output of the amplifier.

Abstract: An offset voltage calibration circuit for use with a digital switching amplifier. The calibration circuit includes an analog-to-digital converter for converting at least one DC offset voltage associated with the digital switching amplifier to digital offset data. A memory stores the digital offset data. Control circuitry controls the analog-to-digital converter. A digital-to-analog converter coupled to the memory receives the digital offset data and generates an offset compensation voltage for applying to an input port of the digital switching amplifier which thereby cancels at least a portion of the at least one DC offset voltage.

Abstract: A LINC amplifier of a radio frequency transmitter provides substantially linear amplification from two nonlinear amplifiers by decomposing the original signal into two constant amplitude envelope, phase varying signals, which, when combined, constructively and destructively interfere to re-form the original signal. The output of the LINC amplifier, which is to be transmitted via an antenna, is an amplified form of the original signal. The LINC amplifier uses a digital control mechanism to control and adapt a digital compensation network that directly compensates for the imperfections of the analog RF environment, including the amplifiers. The mechanism monitors the combined amplifier output and adjusts the signal components in order to precisely compensate for any differences in the characteristics of the separate signal paths which would cause the combination not to accurately represent the original signal.

Abstract: An amplifier includes a first circuit and a second circuit. The first circuit, in a first mode of the amplifier, amplifies an input signal to produce a first output signal. The second circuit is coupled to the first circuit to cause the first circuit to, in a second mode of the amplifier, provide a second output signal that is indicative of a degree of calibration of the amplifier.

Abstract: An extended power ramp table for a power amplifier control loop in a time division multiple access (TDMA) communication system includes a power profile data table and a control data table. The power profile data are used to control transitions of the power amplifier circuit between its on and off states to minimize the number and power levels of spurious and other undesired signals generated by such on and off circuit state transitions. The control data are used to programmably control various performance characteristics of the control loop for the power amplifier circuit, such as controlling the gain of the driver amplifier for the power amplifier control (or reference) signal, controlling the gain and offset of the feedback amplifier for the control loop, and selectively providing a bias current for an external power detection diode. By making the control data user programmable, maximum flexibility in controlling the power amplifier control loop can be achieved.

Abstract: A method for predistorting a digital signal prior to amplification is disclosed in which a look-up table is computed using power values of digital input signal samples as look-up values. The look-up table is preferably a function of pre-measured calibration data. The look-up table is applied to digital input signals for producing the predistorted signal. Computing the look-up table may include determining a set of input power values, obtaining the pre-measured calibration data including an output power data value and phase data value of the amplifier corresponding to each of the input power values, and deriving a set of calibration power values using the output power data values. The calibration power values and the input power values are then used to derive amplitude predistortion calibration values while the phase data values are used to determine phase predistortion calibration values.

Abstract: For determining the operating point of a non-linear amplifier 2 of a communication channel 1, for example of a transponder in a communication satellite, a first input signal I1 is transmitted through the communication channel 1 at a power level PI1 which drives the non-linear amplifier 2 in a non-linear operation mode. In addition, a second input signal i2 is transmitted through the communication channel 1 simultaneously with the first input signal I1. The second input signal i2 is transmitted at a level below the level of the first input signal I1. If the contribution of the second input signal i2 to the total input of the non-linear amplifier is small, the operating point of the non-linear amplifier is determined almost only by the first input signal. Therefore, the output power P02 corresponding to the second signal i2 is determined most strongly by the input power PI1 of the first signal I1.

Abstract: A precision op amp test circuit employs latching relays, the contacts of which are latched open or closed as necessary to make test measurements. The relays' metal contacts ensure low resistance conductive paths, and because the coil of a latching relay need be energized only briefly to latch the contacts, the heating duty cycle of the coils can be kept low to substantially eliminate the accuracy-degrading thermal E.M.F. generated by the heat from the energized coil of a conventional relay. The test circuit is advantageously used for testing both VOS and IB for high precision, low-VOS op amps.

Abstract: An operational amplifier includes transistors for providing a controlled current path. At least one of the transistors is in an isolated well in a substrate. Offset of the operational amplifier is corrected by applying a back gate bias voltage to at least one isolated well and changing impedance of the transistors. The proper back gate bias voltage and transistor impedance are determined by incrementally adjusting the back gate bias voltage and then incrementally adjusting the transistor impedance. Calibration values are stored in register memory. Such calibration may be performed by an auto offset calibration process.

Abstract: A multistage comparator is calibrated to remove quasi-autozero voltages derived from the native comparator offset and autozero switch charge injection offsets. A multistage comparator includes a plurality of series connected amplifiers each having a programmable source, and further including a latch. A calibration method for a multistage comparator includes calibrating the first of a series of amplifiers first for both voltage offset and charge injection errors thereby to remove the quasi-autozero voltage and charge injection offsets.

Abstract: In this invention an integrated operational amplifier is calibrated to optimize phase margin. The calibration is done to correct changes caused by operating temp and supply voltages as well as process variations and aging that can affect the stability of the amplifier. A calibration circuit measures the response of the operational amplifier to a pulse input and controls a feedback impedance to produce an optimized phase margin. The output response to the pulse input is measured at two different times, at a first time close to the transition capturing the peak overshoot from an under damped amplifier and at second time later than the first measurement when the distortions from the under damped ringing have diminished. A quantizer circuit compares the two measure voltages and provides an input to control logic which selects the amount of reactance in the feedback of the operational amplifier.

Abstract: Linearity of an RF/microwave power amplifier is enhanced by an amplitude and phase distortion correction mechanism based upon signal envelope feedback, that operates directly on the RF signal passing through the power amplifier. A phase-amplitude controller responds to changes in gain and phase through the RF/microwave power amplifier signal path caused by changes in RF input power, DC power supply voltages, time, temperature and other variables, and controls the operation of a gain and phase adjustment circuit, so as to maintain constant gain and transmission phase through the RF/microwave power amplifier.