A 2-18 GHz low-noise/high-gain amplifier module

The effectiveness of the two-tier matrix amplifier as a very-low-noise device with very high associated gains across multioctave frequency bands is theoretically and experimentally demonstrated. Experimental modules whose topology is based on a computer-optimized design exhibit an average noise figure of F=3.5 dB with an associated average gain of G=17.8 dB across the 2-18 GHz frequency band. These state-of-the-art results were achieved with GaAs MESFETs whose minimum noise figure is F=2.2 dB at 18 GHz and whose gate dimensions are 0.25×200 μm. The design considerations and the test results are discussed in detail     

Photonic switching modules designed with laser-diode amplifiers

Photonic switching elements are designed from semiconductor optical amplifiers and passive couplers with fiber-to-fiber unity gain and low crosstalk. Designs for a 2×2 and an asymmetric 2×3 element, and several designs for 4×4 elements, are presented. While most amplifier analyses have stressed the importance of ultralow facet reflectivities for high-gain operation, with protection against external reflections with optical isolators, modest facet reflectivities are satisfactory for these elements. It is also shown that substantial amounts of external reflection can be tolerated. The various architectures are compared according to amplifier count, blocking characteristic, broadcast potential, noise power (amplified spontaneous emission), and fault tolerance     

0-40 GHz GaAs MESFET distributed baseband amplifier ICs forhigh-speed optical transmission

We describe distributed amplifiers built using advanced circuit design techniques to improve gain and noise performance at low frequencies. Using these techniques we have developed an amplifier IC with a 0-36 GHz bandwidth and a noise figure of 4 dB at low frequencies. This frequency range starting from 0 Hz makes it possible to use the IC as a baseband amplifier for SDH optical transmission systems and this noise figure is about 1 dB better than conventional distributed amplifiers. We also present another amplifier IC built using our loss compensation technique to improve high-frequency performance of the amplifier. This IC has a 0-44-GHz bandwidth, which is the widest among all reported GaAs MESFET baseband amplifiers     

17 GHz broadband amplifier with 25 dB gain using a 0.3 μmAlGaAs/GaAs/AlGaAs HEMT technology

A broadband amplifier chip based on AlGaAs/GaAs/AlGaAs quantum well FETs with 0.3 μm gate length has been designed and fabricated. The amplifier can be operated with single-ended or differential inputs with an input resistance of 50 Ω. The output signals are differential with both internal load resistances at 100 Ω, the chip area is 1×1 mm², and the power consumption is ~375 mW     

Noise performance evaluation of distributed erbium-doped fiberamplifiers with bidirectional pumping at 1.48 μm

An accurate model for unsaturated fiber amplifiers with fiber background loss is used to determine optimal parameters for distributed amplification in erbium-doped fibers. Pump power at 1.48 μm and erbium-doping levels required for transparency are studied for both unidirectional and bidirectional pumping schemes. An optimal erbium absorption coefficient which minimizes the required pump power is found. However, this case corresponds to the highest amplifier noise figure. The authors conclude that, in practice, distributed erbium-doped fiber amplifiers are not significantly advantageous compared to 980-nm-pumped lumped amplifier schemes     

A Two-Stage IMPATT-Diode Amplifier

The system aspects and packaging of a two-stage FM IMPATT-diode amplifier are described. The amplifier combines the output power of 4 IMPATT diodes in the final stage to provide an output power of greater than 4 W at 6 GHz. The system has a locking bandwidth of greater than 200 MHz with a 16-dB gain and a noise figure of less than 50 dB. Both the design and the experimental performance of the amplifier and each of its stages are discussed. The noise characterization of IMPATT-diode amplifiers, operating as injection-locked oscillators or stable amplifiers, determined the mode of operation for each stage. Included in the paper are experimental results of large-signal noise characterization of both Si and GaAs IMPATT diodes, as are the noise characteristics related to the output power and gain.     

Design of Microwave GaAs MESFET's for Broad-Band Low-Noise Amplifiers

As a basis for designing GaAs MESFET's for broad-band low-noise amplifiers, the fundamental relationships between basic device parameters, and two-port noise parameters are investigated in a semiempirical manner. A set of four noise parameters are shown as simple functions of equivalent circuit elements of a GaAs MESFET. Each element is then expressed in a simple analytical form with the geometrical and material parameters of this device. Thus practical expressions for the four noise parameters are developed in terms of the geometrical and material parameters. Among the four noise parameters, the minimum noise figure F/sub min/, and equivalent noise resistance R/sub n/, are considered crucial for broad-band Iow-noise amplifiers. A low R/sub n/ corresponds to less sensitivity to input rnismatch, and can be obtained with a short heavily doped thin active channel. Such a high channel doping-to-thickness (N/a) ratio has a potential of producing high power gain, but is contradictory to obtaining a low F/min/. Therefore, a compromise in choosing N and a is necessary for best overall amplifier performance. Four numerical examples are given to show optimization processes.     

On power distribution in additive amplifiers

An analysis of the linear power distribution in amplifiers employing the additive amplification principle has been made. It reveals the wide spread of the active devices' contributions to the output power at any one frequency and exposes the band-sharing nature of the additive amplification process in multioctave amplifiers. Reversals in the direction of the energy flow over parts of the frequency band converting active into passive devices were observed. The flat gain response of these amplifiers is found to be the result of a sophisticated process in balancing the active devices' output powers. The computed and measured performance parameters of a 6-18-GHz 2×2 matrix amplifier with emphasis on its experimental multilinear behavior are briefly discussed     

Design and Performance of Monolithic GaAs Direct-Coupled Preamplifiers and Main Amplifiers

The design and performance of a GaAs direct-coupled preamplifier and main amplifier is described. The amplifiers are fabricated by the self-aligned implantation for n/sup +/ -Iayer technology (SAINT) process. The developed preamplifiers have 13-dB gain, 3-GHz bandwidth, and 4.8-dB noise figure for the one-stage amplifier, and 22-dB gain, 2.7-GHz bandwidth, and 5.6-dB noise figure for the two-stage amplifier. The developed four-stage main amplifier has 36-dB gain and 1.5-GHz bandwidth with a power consumption of 710 mW. These amplifiers are promising candidates for application to high-speed data communication systems.     

Monolithic GaAs direct-coupled amplifiers

Monolithic GaAs dc-coupled amplifiers with bandwidths up to 5 GHz are described. The multistage amplifiers include designs having 25-dB gain with 2-GHz bandwidth and 10-dB gain with 5-GHz bandwidth. Analysis of gain, bandwidth, and noise agrees with measurements. Distortion mechanisms are discussed, along with the performance of a low-distortion amplifier.     

GaAs HBT wideband matrix distributed and Darlington feedbackamplifiers to 24 GHz

The designs and performances of a 2-24 GHz distributed matrix amplifier and 1-20 GHz 2-stage Darlington coupled amplifier based on an advanced HBT MBE profile that increases the bandwidth response of the distributed and Darlington amplifiers by providing lower base-emitter and collector-base capacitances are presented. The matrix amplifier has a 9.5 dB nominal gain and a 3-dB bandwidth to 24 GHz. This result benchmarks the highest bandwidth reported for an HBT distributed amplifier. The input and output VSWRs are less than 1.5:1 and 2.0:1, respectively. The total power consumed is less than 60 mW. The chip size measures 2.5×2.6 mm². The 2-stage Darlington amplifier has 7 dB gain and 3-dB bandwidth beyond 20 GHz. The input and output VSWRs are less than 1.5:1 and 2.3:1, respectively. This amplifier consumes 380 mW of power and has a chip size of 1.66×1.05 mm²      

2-20-GHz GaAs Traveling-Wave Amplifier

Single-stage and two-stage GaAs traveling-wave amplifiers operating with flat gain responses in the 2-20-GHz frequency range are described. The circuits are realized in monolithic form on a 0.1-mm GaAs substrate with 50-Omega input and output lines. Complete gate and drain dc bias circuitry is included on the chip. By cascading these amplifier chips, a 30-dB gain in the 2-20-GHz range is demonstrated, with 9+-1dB noise figure.     

Influence of buffer layer thickness on DC performance ofGaAs/AlGaAs heterojunction bipolar transistors grown on siliconsubstrates

The DC performance of GaAs/AlAs heterojunction bipolar transistors (HBTs) grown on silicon substrates with buffer layers ranging from 0 to 5 μm was investigated. Current gain, collector-emitter breakdown voltage, emitter-base and collector-base diode ideality factors, and breakdown voltages were measured as the buffer layer thickness was varied between 0 and 5 μm. The current gain steadily increases with increasing buffer layer thickness until the layer reaches 3 μm. However, the other DC parameters are relatively insensitive to the buffer layer thickness. A small-signal current gain of 60 is typically achieved for devices with 6×6-μm² emitters at a density of 6×10⁴ A/cm² when the buffer layer is ⩾3 μm     

On the performance of low-noise low-DC-power-consumption cryogenicamplifiers

The performance of broad-band low-noise low-dc-power-consumption cryogenic amplifiers have been studied in detail with emphasis on minimizing the power consumption and optimizing the amplifier performance at cryogenic temperature. A general approach is presented for the modeling and amplifier design, which helps in minimizing the power consumption and optimizing the performance of the amplifier. A noise temperature below 9 K and 22-dB gain was experimentally obtained in the frequency range of 4-8 GHz with a total power consumption of 4 mW with commercial GaAs transistors     

Extrinsic base surface passivation in GaInP/GaAs heterojunctionbipolar transistors

The authors demonstrate excellent passivation of the extrinsic base surfaces in GaInP/GaAs heterojunction bipolar transistors (HBTs) having small emitter areas. Passivated devices with an area as small as 4×20 μm² exhibit the highest reported current gain value of 2690 for GaInP/GaAs HBTs, while unpassivated 4×20-μm ² devices exhibit a current gain of only 500. Measured current gains as a function of collector current density are almost identical for devices with varying emitter widths of 4, 6, 8, 12, 16, and 100 μm. The current gains are also nearly identical for devices with varying passivation ledge widths of 1, 2, 3, and 6 μm. These results are contrasted with those of a previously published study reporting surface passivation for a GaInP/GaAs HBT with a large emitter area     

Burnout studies of X-band radar negative resistance transistor low noise amplifiers

GaAs FETs and HEMTs can be configured to give low noise, negative resistance microwave amplification. Such low noise amplifiers have the advantage of an inherent bypass path after device burnout. This feature is potentially useful in radar receiver applications. Test results for prototype LNAs are described, showing burnout energies comparable to those of conventional transmission mode amplifiers using similar devices. Bypass path losses after burnout are around 4 dB, approximately 20 dB less than for a failed transmission mode amplifier.<>     

Super low noise InGaP gated PHEMT

Very high performance InGaP/InGaAs/GaAs PHEMTs will be demonstrated. The fabricated InGaP gated PHEMTs devices with 0.25 × 160/cm² and 0.25 × 300 μm² of gate dimensions show 304 mA/mm and 330 mA/mm of saturation drain current at V_GS = 0 V, V_DS = 2 V, and 320 mS/mm and 302 mS/mm of extrinsic transconductances, respectively. Noise figures for 160 μm and 300 μm gate-width devices at 12 GHz are measured to be 0.46 dB with a 13 dB associated gain and 0.49 dB with a 12.85 dB associated gain, respectively. With such a high gain and low noise, the drain-to-gate breakdown voltage can be larger than 11 V. Standard deviation in the threshold voltage of 22 mV for 160 μm gate-width devices across a 4-in wafer can be achieved using a highly selective wet recess etching process. Good thermal stability of these InGaP gated PHEMTs is also presented     

Design and Analysis of Broadband Dual-Gate Balanced Low-Noise Amplifiers

In this paper, we present three MMIC low-noise amplifiers using dual-gate GaAs HEMT devices in a balanced amplifier configuration. The designs target three different frequency bands including 4-9 GHz, 9-20 GHz, and 20-40 GHz. These dual-gate balanced designs demonstrate the excellent qualities of balanced amplifiers in terms of stability and matched characteristics, while demonstrating higher bandwidth than designs with a single-stage common-source device. Additionally, noise performance is excellent, with the 4-9 GHz LNA demonstrating <1.75 dB noise figure (NF), the 9-20 GHz LNA <2.75 dB NF and the 20-40 GHz LNA <2.5 dB NF. Demonstrating high gain and excellent bandwidth, the dual-gate devices seem a logical choice for the balanced amplifier topology.     

One-chip GaAs monolithic frequency converter operable to 4 GHz

The frequency converter combines a feedback amplifier, a differential amplifier, a double-balanced mixer, a voltage-controlled oscillator, and an IF amplifier on a 1-mm² GaAs chip. The FET circuits were matched by digital IC design rather than by the distributed element network technique, to use the substrate more effectively. Self-aligned WSi/Au gates 1.5 μm long were used, and the resistance in conventional WSi gates was reduced to enhance microwave characteristics. At 4 GHz, the conversion gain is 18 dB, the double-sideband noise is 11.8 dB and the output power is 5.6 dBm     

Flicker noise in GaAs MESFET X-band amplifiers in the temperature range 300 K to 2 K

We report measurements of the noise temperature of small-signal, low-noise X-band GaAs MESFET amplifiers from room temperature down to 2 K, at offset frequencies of several hundred hertz from the carrier and for input carrier powers from -40 to -20dBm. We observe a dramatic increase in the level of flicker noise as these devices are cooled to liquid helium temperatures, in marked contrast to the normally observed decrease in noise temperature of an unsaturated GaAs MESFET amplifier as it is cooled.