Showing papers on "Cascade amplifier published in 1998"

Power- conserving drive-modulation method for envelope-elimination-and-restoration (EER) transmitters

Abstract: A method and a circuit for high-efficiency linear RF-power amplification over a wide range of amplitudes from zero to peak output includes a final RF-power amplifier operating at or near saturation, an RF driver amplifier, a high-level amplitude modulator for the final amplifier, preferably a high-level amplitude modulator for the driver amplifier, and a means for determining the supply-voltage input to the final amplifier and for controlling the amplitude of the drive. The means for determining the supply-voltage input and for controlling the amplitude acts so that the final amplifier drive varies from a minimum level to peak as the desired transmitter output varies from zero to peak. The transmitter is preferably of the envelope-elimination-and-restoration type or the envelope-tracking type.

Dual-band, dual-mode power amplifier

Abstract: A power amplifier circuit for a radio transceiver has a linear mode amplifier and a saturated (nonlinear) mode amplifier, a diplex matching circuit coupled to the linear mode amplifier for impedance matching and for separating transmitted signals in a plurality of frequency bands, a low pass matching circuit coupled to the output of the saturated mode amplifier and means for selectably placing the power amplifier circuit in a linear mode for or a saturated mode, corresponding to digital and analog modes of operation of the cellular telephone, respectively in linear or digital mode, the linear amplifier is biased in the on state and the saturated mode amplifier may be biased in the off state. Similarly, in the saturated or analog mode of operation, the saturated mode amplifier is biased in the on state and the linear amplifier may be biased in the off state. The amplifier circuit may include a switch or circuit, coupled to an output of the diplex matching circuit and the output of the low pass matching circuit, for selectably coupling the first diplex matching circuit output or the low pass matching circuit output to an output line when the amplifier circuit is selectably placed in linear mode or saturated mode, respectively.

Power amplifier output module for dual-mode digital systems

Abstract: A power amplifier output module 200 having low insertion loss and self-shielding properties for dual-mode digital systems is provided. Module 200 has a first power amplifier drive circuit comprising a first power amplifier 220 and a first output impedance matching network having integrated suppression of higher order harmonics 222. A second power amplifier drive circuit comprising a second power amplifier 224 and a second output impedance matching network having integrated suppression of higher order harmonics 226 is also provided. Module 200 also comprises a single diplexer 228 coupled to the first impedance matching network and the second impedance matching network. Module 200 also comprises a single broadband directional coupler 230, coupled to the diplexer 228, for coupling both the first power amplifier drive circuit and the second power amplifier drive circuit. Module 200 provides an integrated solution involving greater performance in a smaller package.

A low-voltage low-power wide-range CMOS variable gain amplifier

Abstract: In this paper, a compact low-power (LP) low-voltage (LV) metal-oxide-semiconductor-only (MOS-only) variable gain amplifier (VCA) is introduced. This amplifier based on complementary MOS (CMOS) transistors operating in strong inversion is composed of a pseudo-exponential current-to-voltage converter, analog multiplier, and output stage. The gain of the amplifier is controlled exponentially by a novel wide-range pseudo-exponential current-to-voltage converter implemented with two back-to-back connected current mirrors exhibiting superb exponential characteristic. Also, a new LV/LP composite transistor is introduced to increase the input dynamic range of the multiplier. The amplifier is fabricated using a 2-/spl mu/m MOSIS n-well process, and its simulation and measurement results are shown in detail.

System and methods for stimulating and training a power amplifier during non-transmission events

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. The mechanism also corrects the component signals using information which can be applied to the amplifiers independent of the signal to be transmitted.

Compensation system and methods for a linear power amplifier

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. The mechanism also corrects the component signals using information which can be applied to the amplifiers independent of the signal to be transmitted.

Dual-band, dual-mode power amplifier with reduced power loss

Abstract: A power amplifier circuit has a driver amplifier stage including a low band driver amplifier and a high band driver amplifier. A final amplifier stage includes a linear mode amplifier for amplifying digitally modulated signals and a saturated (nonlinear) mode amplifier for amplifying frequency modulated (analog) signals. A switching network interconnects the driver amplifier stage and the final amplifier stage. Depending on the desired mode of operation, an appropriate driver amplifier can be coupled to an appropriate final amplifier to most effectively and efficiently amplify analog or digital RF signals in either of a plurality of frequency bands. A matching circuit is coupled to the linear mode final amplifier for impedance matching and for separating D-AMPS (800 MHz band) and PCS (1900 MHz band) digital signals. A power impedance matching circuit is coupled to the output of the saturated mode final amplifier. In one embodiment, an isolator is coupled to the output of one or more of the low band or high band outputs of the duplex matching circuit. In the low band analog path, a duplexer is provided ahead of the coupling means for reducing the RF power requirements on the coupling means. The switching network and input filter stage may precede a driver amplifier stage.

Apparatus and method for amplifying a signal

Abstract: The apparatus includes an amplifier (204) having an input and an output, the amplifier output coupled to an input of a Doherty amplifier (208). The Doherty amplifier (208) includes a control input and a Doherty output. The apparatus further includes a detector (224) having an input coupled to the output of the Doherty amplifier (208). The detector provides a detected signal at its output, to a controller (228), the controller responding to the detected signal by producing a first (230) and second control output (231). The first control output is coupled to a switching regulator (232) input, the switching regulator having an output coupled to the control input of the Doherty amplifier. The second control output is coupled to a control input of a variable attenuator (202), the output of the variable attenuator coupled to the input of the amplifier (204).

Amplifier arrangement with voltage gain and reduced power consumption

Abstract: An amplifier arrangement includes a first amplifier powered by a pair of lower voltage power supplies, a second amplifier powered by a pair of higher voltage power supplies and a drive control device. This amplifier arrangement has both current and voltage gain larger than one. The drive control device includes a regulating device adapted to switch off the first amplifier based on the output signal of the amplifier arrangement, and at least one current link and at least one voltage controlled current source. The transition between the operation of the first and second amplifiers is thereby controlled by the values of the currents of these at least one current links and the at least one voltage controlled current sources.

Controller and associated methods for a linc linear power amplifier

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. The mechanism also corrects the component signals using information which can be applied to the amplifiers independent of the signal to be transmitted.

Power saving device for radio communication terminal

Abstract: A power saving device for a radio commmunication terminal reduces current consumption by changing the number of power amplifying stages. A power amplifier in the radio communication terminal includes a first amplifier (300) for high power and a second amplifier (208) for low power. A signal path selector (209) switches an input signal to an input node of the first or second amplifier in response to a switching control signal. An output path selector selects one of output signals from the first and second amplifiers in response to the switching control signal. An RSSI detector (105) detects signal strength of a signal received from a base station. A controller generates the switching control signal of a first state, when the signal strength is low, to enable the signal path selector to switch the input signal to the first amplifier (300) and enable the output path selector to select the output signal of the first amplifier, and generates the switching control signal of a second state, when the signal strength is high, to enable the signal path selector to switch the input signal to the second amplifier (200) and enable the output path selector to select the output signal of the second amplifier. A power supply (107) blocks a first supply voltage to the first amplifier in response to the switching control signal of the second state, and blocks a second supply voltage to the second amplifier in response to the switching control signal of the first state.

Optical fiber amplifier having variable gain

Abstract: An optical amplifier device intended for WDM light signals comprises a preamplifier (3) and a power amplifier (11) of the optical fiber amplifier type, which are connected in series and have gain curves dependent on the wavelength. A controllable attenuator (5) is connected between the amplifiers (3 and 11) and is controlled by a control device (7). The signal input to the preamplifier (3) has a low power and is amplified to provide an output signal where the signals of the input channels have been amplified with different gains. The input signal of the power amplifier (11) then has a larger power resulting in a gain characteristic different from that of the preamplifier (3). By adapting the attenuation of the attenuator (5) for variations in the input signal the gain characteristic of the power amplifier (11) can be set so that the signal output from the amplifier device has a spectral dependence that is the same as the original spectral dependence obtained without variations. Also, the same spectral dependence can be maintained when the pump light power of the power amplifier is changedand then the total amplifier gain is changed, by adapting the attenuation of the attenuator (5) so that the gain of the power amplifier is not changed. In the amplifier the lower possible noise from the preamplifier stage is added to the input signal and the full output power is always available from the power amplifier. If the input signal is e.g. increased the SNR of the signals passing through the amplifier is correspondingly improved. This improves the performance of an optical network in which the amplifier is used.

Broadband flat gain optical amplifier

Abstract: An optical amplifier that receives an optical signal at an input of the optical amplifier is arranged so that it amplifies the signal and then adjusts the level of the amplified input signal to a predetermined level. The optical amplifier, which includes a filter to substantially decrease the wavelength dependence of the optical amplifier, then amplifies the adjusted signal and supplies the resulting signal to an output.

Partial or complete amplifier bypass

Abstract: A power amplifier circuit arrangement particularly useful for portable phones used in wireless systems. A power amplifier stage can be partially or completely bypassed so that multi-stage amplifiers can be built that allow wide dynamic range of power amplification to be obtained efficiently. A switch at the input of an amplifier stage couples an input signal either to an amplifier or to a bypass path. The output of the amplifier is coupled to a first impedance-transforming network. The bypass path includes a second impedance-transforming network. A third impedance transforming network couples the outputs of the first and second impedance transforming networks. The impedance transforming networks are constructed and arranged so that input and output signals see the correct load regardless of whether the amplifier is used or bypassed. Using the principles of this invention, multi-stage amplifiers can be constructed including input and bypass attenuators to achieve a wide range of gain levels.

A new high-efficiency and super-fidelity analog audio amplifier with the aid of digital switching amplifier: class K amplifier

Abstract: This paper presents an audio amplifier that simultaneously has the advantages of digital and analog amplifier. The high efficiency is achieved by the digital amplifier, which is playing a role of dependent current source. The high fidelity is guaranteed by the analog amplifier playing a role of independent voltage source. Experimental results show that the proposed amplifier has 0.005% total harmonic distortion (THD) and around 90% power efficiency at 50 W output.

RF power amplifier with variable bias current

Abstract: An RF power amplifier with variable bias current is disclosed. The RF amplifier includes a peak detector that detects the peak level of the amplifier input signal. The peak detector generates an output signal in response to the peak level of the amplifier input signal. A bias voltage level setting circuit coupled to the peak detector receives the peak detector output signal and generates a bias voltage in response to the peak detector output signal. An amplifier circuit coupled to the bias voltage level setting circuit receives the bias voltage and the amplifier input signal, and generates an output signal in response to the bias voltage and the amplifier input signal. The disclosed RF amplifier allows amplification of RF signals with high linearity and high efficiency at varying power levels, and extends the maximum power capability of the amplifier.

Class D amplifier no low pass filter feedback with zero phase delay

Abstract: A circuit for generating an accurate reproduction of the output of a Class D amplifier for error-correction purposes includes a reference signal amplifier circuit. The reference signal amplifier circuit includes an op-amp configured as a differential amplifier that combines the digital outputs of the internal output stage of the amplifier into a single reference signal. By reducing the bandwidth of the op-amp, switching noise is removed from the digital signals, without adding any phase shift to the generated reference signal. In addition, by using the digital signals directly from the output stage rather than the filtered analog outputs of the amplifier, distortion due to external speaker-induced back-EMF is prevented. The reference signal can then be compared to the original signal input to the amplifier for error-correcting purposes.

A low-cost class-E power amplifier with sine-wave drive

Abstract: We present a 400 W class-E amplifier for industrial applications. The transistor is the International Rectifier IRFP450LC power MOSFET. The amplifier operates at 13.56 MHz and uses a drive level of 12 W to attain a drain efficiency of 86% and an overall efficiency of 84%. All harmonics are more than 40 dB below the carrier.

System for enabling a full-bridge switch-mode amplifier to recover all reactive energy

Abstract: A full-bridge amplifier that is able to provide power to all types of loads. The fill-bridge amplifier according to the present invention recovers reactive energy produced by capacitive loads instead of having the reactive energy be dissipated in the switches of the amplifier, thereby causing device failure. In one embodiment, two inductors and four diodes are added to the conventional full-bridge topology. Furthermore, a full-bridge amplifier according to an embodiment of the present invention is able to operate over a broad-band of radio frequencies.

Rectangularly driven class-A harmonic-control amplifier

Abstract: A rectangularly driven class-A harmonic-control amplifier (rHCA) is studied, which combines the advantage of high device drain efficiency (/spl eta//sub D/) of a switched-type amplifier with the advantage of high gain (G) of class-A operation, thus maximizing its power-added efficiency (PAE). In this rHCA, harmonics are controlled such that drain-to-source voltage becomes half-sinusoidal. This reduces the necessary supply voltage without degrading output power. In comparison with a class-F amplifier using the same transistor, the realization of such an rHCA has demonstrated 0.4-dB larger output power, 3.8-dB increased gain, 4% higher PAE, and 22% lower drain supply voltage at 1.62 GHz.

High speed, fine-resolution gain programmable amplifier

Abstract: An integrated circuit differential amplifier with a digitally controllable gain. In a preferred embodiment, the differential amplifier employs first and second transconductance (gm) amplifiers and a digital to analog converter (DAC). The first gm amplifier converts a differential input voltage into a differential output current and the second gm amplifier converts the differential output current into a differential output voltage. A digital input code is applied to the DAC to generate an analog output voltage that is applied to one of the gm amplifiers to control its transconductance to thereby control the gain of the differential amplifier. The second gm amplifier employs a pair of low impedance feedback paths between input/output terminals of opposite polarity. The gain of the differential amplifier is thus a function of the ratio of the transconductance of the first gm amplifier to that of the second gm amplifier. Preferably, the same circuit topology is employed for both gm amplifiers, leading to a process- and operating temperature-insensitive differential amplifier gain. Additional gm amplifiers may be connected in parallel with the first gm amplifier to enhance gain. The load resistance presented by the second gm amplifier is preferably kept low to afford high speed operation.

Cascaded error correction in a feed forward amplifier

Abstract: A feedforward amplifier system including a main amplifier and first and second error amplifiers, and wherein the first error amplifier is itself a feedforward amplifier whose operation is corrected by the second error amplifier. With appropriate selection of circuit components the operating power required by the amplifier system, and hence the size of the package in which it is contained, may be reduced up to one-third.

Hybrid system for control and monitoring of an amplifier

Abstract: A hybrid system (18) for control and monitoring of an amplifier (330) is provided. The hybrid control system (18) includes an analog control subsystem (81) and a digital control subsystem (82). The analog control system provides an automatic gain control loop for maintaining the gain of amplifier (330) at a predetermined level. The digital control subsystem (82) monitors a plurality of operating characteristics of amplifier (330) and commands the analog control subsystem (81) to reduce the gain of amplifier (330) responsive to certain predetermined fault conditions. The digital control subsystem (82) shuts down amplifier (330) responsive to other predetermined fault conditions. The digital control subsystem (82) also controls the power-on sequence and power-down sequence for amplifier (330), insuring that the gate bias voltage is first applied or maintained before the drain voltage is applied or removed.

High-fidelity and high-efficiency analog amplifier combined with digital amplifier

Abstract: This invention provides an analog audio amplifier having both excellent linearity and high efficiency, which is combined with digital amplifier. The analog-digital combined amplifier comprises a class A, class B or class AB type analog amplifier serving as an independent voltage source; and a class D type digital amplifier serving as a dependent current source thereof, wherein the analog amplifier and the digital amplifier are connected to each other.

Television tuner, tuner integrated circuit and method of controlling television tuner

Abstract: There is provided a television tuner including a first amplifier for amplifying received signals having frequencies of VHF-L and VHF-H bands, a first converter for converting a frequency of the received signals having been amplified by the first amplifier, a second amplifier for amplifying a received signal having a frequency of UHF band, a second converter for converting a frequency of the received signal having been amplified by the second amplifier, a signal transmitter for transmitting an operation switching signal by which the VHF-L band, the VHF-H band, or the UHF band is selected, a detector for detecting that none of the VHF-L and VHF-H bands is selected, based on data about the VHF-L and VHF-H bands, represented by the operation switching signal, and a driver for driving the second amplifier and pausing the first amplifier when the detector detects that none of the VHF-L and VHF-H bands is selected, and pausing the second amplifier and driving the first amplifier when the detector detects that one of the VHF-L and VHF-H bands is selected.

Active compensating capacitive multiplier

Abstract: A compensated amplifier, for amplifying an input signal applied to an input node to provide an output signal at an amplifier output node. The compensated amplifier includes a first amplifier stage having an internal node as an input thereto and having a first stage output node. Also included is a second amplifier stage coupled to the first amplifier stage, having the input node as an input thereto and providing the output signal at the amplifier output node. A capacitor is coupled between the output node and the internal node.

Power amplifier with variable input voltage source

Abstract: A power amplifier circuit (10) utilizes a step-wise variable voltage source (22) to improve amplifier (14) operating efficiency. In one preferred embodiment, an input signal to the step-wise variable voltage source is obtained by observing an operating characteristic of the amplifier. In an alternate preferred embodiment of the present invention, a characteristic of the input signal driving the amplifier stage is used to form an input signal to the step-wise variable input voltage source.

Dual gain amplifier circuit

Abstract: A dual gain amplifier provides separate gains so that the amplifier's input characteristics are unaffected by the gain selected. The dual gain amplifier comprises a first input amplifier and a third amplifier connected in cascade, and a second input amplifier and a fourth amplifier connected in cascade. A first LC circuit is connected in parallel to a second LC circuit which are both connected to the third amplifier. Likewise, a third LC circuit is connected in parallel to a fourth LC circuit which are connected to the fourth amplifier. The first and third LC circuits have a first quality factor and the second and fourth LC circuits have a second quality factor. The dual gain amplifier switches from a first state in which only the first and third LC circuits conduct to a second state in which all four LC circuits conduct.

Apparatus and method for pre-distortion correction of a power amplifier stage

Abstract: In an amplifier circuit having an amplifier path, a new pre-distortion arrangement is provided. The amplifier circuit includes a signal source, an intermediate amplifier stage, and a power amplifier stage connected sequentially, in series along the amplifier path. The power amplifier stage includes one or more amplifiers operationally connected in parallel, and one or more pre-correction circuits. Each of the amplifiers subjecting an inputted signal to shifts away from their intended values. Each of the pre-correction circuits is associated with one of the amplifiers and connected between an output of the intermediate amplifier stage and the associated amplifier. Each of the pre-correction circuits pre-distorts the signal input to the associated amplifier to compensate for the distortion caused by the associated amplifier. Also, preferably, pre-correction circuits are associated with, and in series with, each of the amplifier stages for pre-distorting the signal input to the associated amplifier stage to compensate for the distortion shifts of the associated amplifier stage.

Apparatus and method for implementing a low-noise amplifier and mixer

Abstract: Disclosed is an apparatus for modifying a radio frequency signal. In one embodiment, the apparatus includes a mixer, an amplifier module and an interface circuit. The mixer is configured to receive a first signal having a first frequency and a second signal having a second frequency, and to output a third signal which is a function of the first and second signals. The amplifier module includes a first amplifier stage and a second amplifier stage and is configured to amplify a communications signal which is then input into the mixer as the first signal. The first and second amplifier stages are in communication via a first signal path and a second signal path. The interface circuit is interposed between the mixer and the amplifier module, and inserted into the second signal path so that a DC bias current flows from the first amplifier stage through the interface module into the second amplifier stage.