An amplifier with bipolar transistors and extremely high input impedance

A differential amplifier with unity gain, less than 10 to 50 mV offset, and a dc input resistance of 900 M/spl Omega/ was examined using complementary bipolar transistors.     

Intermodulation distortion in a multiple-quantum-well semiconductor optical amplifier

The measurement of intermodulation distortion (IMD) induced by carrier-density modulation in a multiple-quantum-well (MQW) semiconductor amplifier is reported. The results show that MQW amplifiers have 15 dB less IMD than conventional buried-heterostructure semiconductor amplifiers. The IMD is dependent on the output power of the amplifiers, which confirms that the carrier-density modulation is the dominant nonlinear mechanism in MQW amplifiers. In addition, the results show that, unlike conventional buried-heterostructure amplifiers, MQW amplifiers have at least two time constants (200-250 ps and <10 ps) for the gain recovery process.<>     

A high input impedance buffer amplifier using bipolar transistors

The input impedance of conventional emitter follower circuits is limited due to the finite value of the passive emitter resistance, shunting effect of biasing resistors and that of intrinsic collector to base feedback admittance and also to the fall in current amplification factor at low operating currents. Further, the input admittance is frequency dependent because the device parameters involved therein are themselves frequency dependent. However, the shunt positive feedback incorporated in such circuits minimizes the shunting effect of the biasing network and also that of the intrinsic feedback admittance. The simulation of negative capacitance across the input terminals nullifies the effect of the presence of the otherwise positive capacity. This technique extends the bandwidth over which the input impedance remains constant. A typical buffer amplifier circuit employing five conventional epitaxial planar bipolar silicon transistors has been described in the present communication. The input impedance of which is found to be constant over a frequency range of 10 HZ to 2 KHz and its magnitude is about 25MΩ.     

Transistor input distortion and emitter degeneration

In the design of class A transistor amplifiers it is desirable to be able to predict and control the amount of distortion produced by the nonlinearity of the transistor input characteristic. This note presents an extension of a previously published method, to include the effects of emitter degeneration. The result provides a convenient means of determining the degenerations required to reduce the second-harmonic distortion to a given level.     

Differential amplifier input impedance and Blackman's impedance relation

Recently the input impedance of a differential amplifier was derived and discussed. This correspondence derives similar results using a different approach, namely, Blackman's impedance relation, and generalizes earlier observations. The results provide an alternative activeRCrealization of a bilinearRLimpedance. Various all-pass networks are also analyzed.     

RF power amplifier employing a frequency-tunable impedance matching network based on coupled inductors

Coupled inductors can be used as tunable inductances. Employing coupled inductors in the output impedance matching network of an RF power amplifier leads to superior performance when operating in more than one frequency band. As proof of this concept, the design of a dual-band RF power amplifier for the 200 and 300 MHz bands is presented. Simulation and measurement results validate the technique.     

The relationship between noise and impedance matching in a negative resistance amplifier

It is shown that a relationship exists between the impedance matching at the output port of a negative resistance amplifier and its noise performance. The class of amplifiers considered is characterized by a lossless embedding network and by negative resistances having the same noise exchangeable power.     

An RF electronically controlled impedance tuning network design and its application to an antenna input impedance automatic matching system

A novel design is proposed for an electronically tunable impedance unit. The prototypes include lumped elements, but no electromechanical control methods. The devices can tune many different complex impedances at minimum manufacture costs. Two antenna input impedance automatic matching systems are also presented, based on the tuning network. One includes a simplified version of the generic tuner, which can achieve good matching levels between the antenna and the power module with low losses. In a more complete version, an application specific integrated circuit control unit is developed including a complex search algorithm. In order to obtain a good matching level, both systems require a control module to select the proper tuner impedance configuration. The measurements and results of both constructed prototypes are presented. The designs were carried on terrestrial trunked radio mobile stations in the 380-400-MHz frequency band and supported high power levels (greater than 40 dBm).     

Variability analysis of impedance matching network

This paper investigates the L network impedance matching analytically. The equation describing the effect of load impedance variation on the impedance matching performance is derived. The deviation from perfect match is proportional to the variation in load reflection coefficient. However, if the load impedance is too large or too small, resulting in a large reflection coefficient, the solution to the impedance matching problem will have poorer quality in term of variability. The variability factor increases rapidly when the load reflection coefficient is larger than 0.7. A small variation in the load impedance will cause a large deviation from perfect match.     

Optimization of input impedance and mechanism of noise suppressionin a DC SQUID RF amplifier

The optimal input impedance and noise of a DC SQUID RF amplifier at frequencies of the order of 1 GHz with a resonant input matching circuit have been studied analytically, numerically, and experimentally. A model for noise temperature and power gain has been developed for the practical resonant input tank circuit. A new effect of the output noise increasing or decreasing with changing the sign of voltage-to-flux transfer coefficient has been observed experimentally and explained analytically. The different values of noise temperature for the opposite dV/dΦ values have been interpreted using a model with partially correlated current and voltage noise sources. The equivalent layout for optimal input matching of a SQUID amplifier comprising series and parallel resonant circuits has been presented. Using such a matching circuit and SIS junction as a signal source the SQUID amplifier noise temperature about 1 K has been measured at 1.1 GHz     

The effect of excess gate current on input impedance of a JFET amplifier

When JFET is used as an amplifier, it should be regarded that the effect of excess gate current on the input impedance is changed by gain of the amplifier. The input impedance or conductance with gain of the JFET amplifier is experimentally analyzed applying small signal equivalent circuit.     

Power amplifier with low average current and compact output matching network

A power amplifier with a compact output matching network and a high average operating efficiency owing to its control circuits which enable the dynamic control of the quiescent current is presented. The microwave monolithic integrated circuit of the power amplifier was designed and implemented, in order to verify the output matching network and control circuits for the 1.88-GHz band. The power-added efficiency for an average power-usage of the proposed amplifier is almost twice that of conventional power amplifiers (3.74% versus 6.86%) in urban areas.     

A MEMS reconfigurable matching network for a class AB amplifier

This letter presents the design of a reconfigurable amplifier with an adaptive matching network implemented by shunt MEMS switches. In particular, the MEMS switches are used as capacitive stubs in double-stub matching circuit designs. The effective capacitance of the switches can be varied by switch activation which results in a change of the matching configuration. The RF response of the adaptive matching network is studied and the power performance of the amplifier is presented.     

放大器的新型谐波匹配网络的研究与实现

在现代通信系统中,功率放大器起着重要的作用并消耗大量的功率,因此,提高放大器效率对于节约整个系统的能量是尤为重要的。本文的目标是找到放大器在谐波频率处的匹配阻抗,并最终构建放大器的谐波匹配网络,以使放大器达到其最高效率。本文采用了负载牵引技术,使用自动控制调节器对阻抗进行控制。首先对自动调谐器进行校准,得出其内部的不同坐标与相应阻抗的对应关系。然后通过对自动调谐器的控制来控制和改变二次谐波和三次谐波的负载阻抗,找到谐波匹配阻抗以使放大器在基频的效率达到最大。最终,根据谐波匹配阻抗来构建放大器的谐波匹配网络。实验结果表明：通过过谐波匹配,可以使放大器的效率提高2.13%。采用本文所使用的方法,放大器的功率提高了2.13%,实现了通过谐波匹配网络来提高放大器效率的目标,证明了本文所采用的方法的可行性。     

Optimum design of a wideband planar N-way fork power divider with arbitrary power division and input-to-output impedance matching

An effective design procedure based on method of least squares is proposed for multi-section and multi-output fork power divider/combiner with arbitrary power division ratios among its outputs in a specified frequency bandwidth together with impedance matching among its arbitrary source/load impedances. Transmission and scattering matrices are obtained for its equivalent circuit. An error function is constructed based on design specifications on its output power division ratios, isolations among output ports, return losses at its input and output ports and source/load impedances in a desired frequency bandwidth. The design procedure is fully developed, which determines the widths and lengths of microstrip line sections and resistor values. A design example is described for unequal power division ratio and unequal input/output impedances. A 3-section and 3-output fork power divider is designed for equal power division and load/source impedances for 2–12 GHz band. It is fabricated and measured. Variations of its transmission coefficients are less than 0.5 dB, isolations at its outputs are better than −15 dB and reflection coefficients at its ports are better than −10 dB. Excellent agreement is observed among the results of the proposed design procedure, full wave computer software and measurement data.     

An analysis of low-frequency second-order distortion in bipolar transistors applied to an amplifier

A distortion theory for bipolar transistors is applied to reduce low-frequency second-order distortion M/SUB 2/ in an amplifier. An equation for M/SUB 2/ is developed in terms of the physical parameters of the transistor. It is found that M/SUB 2/ depends critically on generator resistance that can be optimized for the transistor studied. The theory and this finding are then applied to the distortion producing Darlington pair in an amplifier, and an optimal value of base resistance for the second transistor is predicted and verified to improve M/SUB 2/ by 30 dB at 5 MHz for the pair. The corresponding improvement in the amplifier is 17 dB (from -50 to -70 dB) at 5 MHz and is accompanied by a small, acceptable degradation in M/SUB 3/ of 3 dB at high frequencies.     

A 3-10-GHz low-noise amplifier with wideband LC-ladder matching network

Reactive matching is extended to wide bandwidths using the impedance property of LC-ladder filters. In this paper, we present a systematic method to design wideband low-noise amplifiers. An SiGe amplifier with on-chip matching network spanning 3-10 GHz delivers 21-dB peak gain, 2.5-dB noise figure, and -1-dBm input IP3 at 5 GHz, with a 10-mA bias current.     

10-Gb/s driver amplifier using a tapered gate line for improved input matching

The use of a tapered gate line in a distributed amplifier (DA) is investigated and applied to the design of a GaAs monolithic microwave integrated circuit 10-Gb/s optical driver amplifier. Improved input matching is achieved near the cutoff frequency by reducing the characteristic impedance successively along the gate line toward the termination. With the improved matching conditions, the voltage ripple on the final resistor termination is reduced. The degree of tapering that can be employed is limited by the low-frequency gain and matching requirements. Detailed analysis and simulation results are used to investigate the advantage of this technique. To demonstrate its practical use, the performance of a 10-Gb/s DA fabricated with Filtronic Compound Semiconductor's 0.5-/spl mu/m pseudomorphic high electron-mobility transistor technology is presented.     

AlGaAs/GaAs bipolar transistors with a modulation-doped superlattice emitter

A new emitter-base concept for heterojunction bipolar transistors is proposed and demonstrated. The abrupt or graded emitter-base heterojunction drawbacks are circumvented by means of a modulation-doped stack of ternary compound alternating with binary compound layers. This stack provides efficient barriers to the hole current while preserving good diode characteristics. These concepts are demonstrated by experimental results on small-area devices with a common-emitter gain of ~40 and a collector-emitter voltage offset of ~80mV.     

一种基于恒定电流技术的具有低功耗和低失真的轨导轨输入输出放大器

本文提出了一种应用于音频信号处理的具有恒定的跨导Rail-to-Rail放大器,并且恒定跨导是通过一种恒定电流技术来实现。此技术是基于差分输入对工作在弱反型区。对于工作在弱反型区的MOSFET具有低失调和低功耗的优势。采用标准的0.35微米的CMOS工艺对电路进行流片,此芯片占有面积75×183 μm2。测试结果表明：在3.3V电源电压下,电路最大功耗为85.37mW;在2kHz时总谐波失真为1.2%。