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In this paper, two types of avalanche photodiode (APD) are compared, namely, a P-down APD using an inverted structure and a P-up APD using a conventional structure. Comparison between those two types of APD was made and differences between them were pointed out. We find that the inverted APD structure can prevent undesirable edge breakdown and improve high-speed performance. A maximum 3-dB bandwidth of 23 GHz and a gain–bandwidth product of 276 GHz are obtained for the P-down APD. For larger capacity applications, the P-down APD can play a greater role than the P-up APD. [ABSTRACT FROM AUTHOR]

This study presents a low power recycling folded cascode operational transconductance amplifier (RFC OTA) with enhanced transconductance. The proposed structure uses a novel input stage biased by a DC current source in addition to a floating voltage source. The adoption of a floating voltage source splits DC biasing current asymmetrically between the inner and outer differential pair of the input stage. This leads to an enhanced gain factor of recycling current mirrors resulting in improved transconductance. The uniqueness of the proposed structure is that a tuneable transconductance is achieved simply by adjusting the value of a floating voltage source. The proposed RFC OTA is simulated using 0.18 μm CMOS process. Simulation result shows 520% and 13.7 dB advancement in gain-bandwidth (GBW) product as well as gain compared to the FC OTA counterpart. [ABSTRACT FROM AUTHOR]

HgCdTe avalanche photodiodes (APD) have been demonstrated to be one of the most promising paths for low flux and high speed applications. The bandwidth of HgCdTe e-APD has been theoretically predicted to be independent of the gain, own to its strongly dominant electron multiplication. However, when the photocurrent is high, a large number of electrons exist in the depletion region, and the electrical field in the depletion region might collapse due to the space charge effect, thus limiting the increase of the gain-bandwidth product. In this work, the structure of the device was optimized by simulation, and the effect of the light injection dose on the electric field and bandwidth of the device was studied. Finally, a mid-wavelength infrared HgCdTe e-APD device whose bandwidth hardly decreases with the increase of gain is fabricated. The response bandwidth of the APD is about 480 MHz @ gain = 625, corresponding to a gain-bandwidth product of 300 GHz. [ABSTRACT FROM AUTHOR]

InAlAs/InGaAs avalanche photodiodes (APD) were simulated using physical device models, then designed and fabricated to detect light in the wavelength range from 1.3 to 1.55 µm. DC characterisation under dark and light conditions were performed at room temperature to measure and investigate the performance of the APD. High‐frequency characterisation was carried out on the device to extract the diode intrinsic and extrinsic parameters. The work reported here focuses on the dark and light physical device simulations (both under DC and AC conditions) which were accomplished using Atlas SILVACO tool. The effect of electron velocity overshoot was considered for accurate bandwidth modelling. All measured data are in excellent agreement with the modelled ones. The internal device gain of the APD is 45 at −23.5 V leading to a ∼220 GHz gain–bandwidth product. This successful APD model can be exploited to further improve the diode structure for higher data rate applications beyond 10 Gb/s. [ABSTRACT FROM AUTHOR]

In this paper, a new topology is proposed for designing and analyzing a transimpedance amplifier (TIA) based on active voltage-current feedback. The proposed topology reduces the input and output impedances by using a common source transistor as a voltage-current feedback. In this topology instead of using a resistor to convert current to voltage, we convert transistor transconductance into transimpedance, and then by applying an electrical current to the drain the required voltage appears at the gate terminal. Simulation of the designed TIA for 1.8 V 0.18 µm CMOS technology shows that the gain of 59 dBΩ with 1 dBΩ gain ripple of the bandwidth of 7.9 GHz can be achieved. While the whole TIA circuit consumes 18 mW from 1.8 V power supply the simulated average input current noise spectral density is about 23 pA / √ Hz within the TIA frequency band. In this topology new tradeoffs are possible which make a further degree of freedom which are not available in previous topologies. [ABSTRACT FROM AUTHOR]

This paper presents a 2.4/5.2/5.8 GHz, triple-band, common-gate, cascode CMOS low-noise amplifier using only a band-selection switch that alters the equivalent LC tank and thus the resonant frequencies of the tank. The aspect ratio of the cascode MOS device is designed to optimize the gain-bandwidth product of the proposed low-noise amplifier so that wideband performance can be achieved. The proposed triple-band low-noise amplifier is suitable for use in the frequency-partitioning scheme that utilizes a wideband frontend with three medium-sized bands, to implement wideband RF frontend architecture for software-defined radio. Theoretical analyses of the input impedance, noise factor, and three resonant frequencies of the switched LC tank that show good agreement with the experimental results are also presented. The measured 3-dB bandwidths of the three bands of 2.4, 5.2, and 5.8 GHz are 720, 1080, and 910 MHz, respectively, which demonstrate the feasibility of the proposed design methodology. The proposed low-noise amplifier provides forward gains ( $$\left| S_{21} \right| $$ ) of 10.6, 17.4, and 15.6 dB, with minimum noise figures of 4.96, 5.16, and 5.57 dB, for the three operation bands. A test chip with a die area of $$0.64\,\hbox {mm}^{2}$$ was fabricated using a 0.18- $$\upmu \hbox {m}$$ RF-CMOS process. The proposed triple-band low-noise amplifier consumes only 3.6 mW, excluding the buffer, from a supply voltage of 1.8 V. [ABSTRACT FROM AUTHOR]

This paper presents a dual-wideband, common-gate, cascode low-noise amplifier (LNA) using gain-bandwidth product optimization technique. This approach shrinks the aspect ratio of the cascode MOS device, thereby reducing the equivalent parasitic capacitance of the resonator load to optimize the gain-bandwidth product of the LNA. The input impedance of the proposed LNA is analyzed, and the noise factor is well predicted through analytical equations. Measurement results that show well agreement with post-simulation results demonstrate the feasibility of this technique. In low-band mode, experimental results presented a maximum $$\left| S_{21} \right| $$ of 13.4 dB over a $$-$$ 3-dB bandwidth of 3.1-4.8 GHz with a minimum noise figure of 4.5 dB. In high-band mode, the proposed LNA achieved a maximum $$\left| S_{21} \right| $$ of 13.6 dB with a minimum noise figure of 6.2 dB over a $$-$$ 3-dB bandwidth of 7.3-9.4 GHz. A test chip with a die area of 0.83 mm $$^{2}$$ was fabricated using a 0.18 $$\upmu $$ m CMOS process. The proposed dual-wideband LNA consumes 9.1 mW, excluding the buffer, from a supply voltage of 1.8 V. [ABSTRACT FROM AUTHOR]

Mid-wavelength infrared (MWIR) HgCdTe avalanche photodiodes (APD) have critical applications in the areas of sensing and imaging. However, most of the reports on HgCdTe have been focused on the DC characteristics such as the dark current, responsivity and gain. This work studied the frequency response of the MWIR HgCdTe APD, which is an important figure of merit for free space communication and dual frequency comb spectroscopy applications. The device with a 20 μ m diameter shows a low dark current of around 10−13A at low reverse bias, and achieves a gain up to 1356 under −11.4 V, along with a low excess noise of 1.3 at 78 K. The responsivity is about 1.48 A/W at 4.5 μ m wavelength under 0 V. The response bandwidth of the APD is about 635 MHz under −1 V. The device is characterized in detail to probe the limiting factors of the bandwidth. At last, an upside-down structure that enables APDs to realize higher gain-bandwidth products is proposed. It indicates that a bandwidth of more than 30 GHz can be realized with 1 μ m intrinsic region. Therefore, this investigation could offer a perspective on improving the bandwidth of HgCdTe APDs and advance the technology in free-space optical communication and other emerging areas. [ABSTRACT FROM AUTHOR]

This paper describes the design and analysis of broadband transimpedance amplifiers (TIAs) based on Regulated Cascode (RGC) configuration. The focus is to deal with bandwidth restriction occurring in optical receivers coming from TIA input parasitic capacitances. Despite the conventional method for broadband RGC TIA design that a ladder matching network is employed to isolate the input capacitance of TIA and the photodiode capacitance, the proposed TIA eliminates the effects of these parasitic components by absorbing them in a T-matching network. The conventional broadband RGC TIA is analyzed and the disadvantages of the ladder matching network is demonstrated in a TIA design example. The proposed RGC TIA is simulated on 0.18-μm standard RF CMOS process. The simulation results presented show that the Gain-Bandwidth product (GBW) is extended by a larger factor compared to that of the conventional broadband RGC TIA while the biasing conditions and the value of the photodiode capacitance are considered the same. [ABSTRACT FROM AUTHOR]

A class AB one‐stage fully differential amplifier is described. It includes adaptive biasing techniques to the conventional class A differential amplifier that improve linearity, gain‐bandwidth product and slew rate, maintaining the same DC bias currents and supply voltage requirements. Boosting of dynamic currents for large input signals takes place at the output branches, without internal replication of these currents. This leads to a nearly 100% current efficiency. Measurement results for a 0.5 μm CMOS test chip prototype validate the proposal. [ABSTRACT FROM AUTHOR]

Aperture coupled antennas are studied in terms of Gain-Bandwidth Product (GBWP). To understand whether resonant or non-resonant slot coupled antenna has better performance, several antenna designs with different slot shapes are optimized and compared to each other. Even for a pin-feed microstrip antenna, we show that there exists a substrate height and aspect ratio for optimal GBWP. Based on this analysis, a stacked aperture coupled antenna is designed and optimized for high gain and wideband for Ku band downlink (10.8-12.75 GHz) applications. The designed antenna exhibits 9.5 dBi broadside gain with 80° half power beam width and almost 30% bandwidth. Ku-band gain ripple is less than 0.5 dB. The antenna is built and measured. Several figure-of-merits based on GBWP have been defined to compare its performance with earlier works. Proposed antenna can be used in demanding high gain, wideband, beam scanning array applications. [ABSTRACT FROM AUTHOR]

Abstract: A split compensation for inverter-based self-biased two-stage amplifier is presented in this paper with detailed quantitative analysis. The conventional miller capacitor is split into two parts to accomplish frequency compensation. With the split compensation, the non-dominant poles and their corresponding Q-values are independent on the parasitic parameter, moreover, this compensation together with inverter-based input stage and the self biased technique improves the performance such as DC gain, gain-bandwidth product, stability and sensitivity. The proposed amplifier has been implemented in a SMIC 0.13μm CMOS process and the chip area is 0.10×0.14mm2. It achieves 10.2-MHz gain-bandwidth product when driving a 20-pF capacitive load dissipating 97.2μW power at 1.2V supply, which shows an improvement in IFOMS and IFOML performance. [Copyright &y& Elsevier]

The cascode amplifier has the potential of providing high gain and high bandwidth simultaneously. However, the design is not as intuitive as one might at first think. In this paper, we present a detailed analysis of the single cascode amplifiers. The relationship between gain and bandwidth is important. When used to achieve maximum bandwidth the voltage gain of the common-source stage is close to unity. However, when the cascode is designed to obtain a high voltage gain, then the gain-bandwidth trade-off, typical in the common source amplifier, reappears. This analysis is used to provide the basis for practical cascode amplifier design. [ABSTRACT FROM AUTHOR]

Performance analysis and design methodology of an HBT cascode amplifier with series RLC loss compensation network are reported in this article. The series RLC loss compensation network enhances the gain-bandwidth product of the cascode amplifier. For comparison, cascode amplifiers with and without RLC loss compensation network are designed and fabricated on 2 μm InGaP/GaAs HBT technology. The measurement results show that the gain-bandwidth product for the amplifier with loss compensation network is increased by a factor of 4, compared with the conventional amplifier. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2410–2413, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24611 [ABSTRACT FROM AUTHOR]

A mask programmable technology to implement RF and microwave integrated circuits using an array of standard 90-nm CMOS transistors is presented. Using this technology, three wideband amplifiers with more than 15-dB forward transmission gain operating in different frequency bands inside a 4-22-GHz range are implemented. The amplifiers achieve high gain-band- width prroducts (79-96 GHz) despite their standard multistage designs. These amplifiers are based on an identical transistor array interconnected with application specific coplanar waveguide (CPW) transmission lines and on-chip capacitors and resistors. CPW lines are implemented using a one-metal-layer post-processing technology over a thick Parylene-N (15μm) dielectric layer that enables very low loss lines (~0.6 dB/mm at 20 GHz) and high-performance CMOS amplifiers. The proposed integration approach has the potential for implementing cost-efficient and high-performance RF and microwave circuits with a short turnaround time. [ABSTRACT FROM AUTHOR]

A theory is given on maximizing the product of energy gain and bandwidth for broadband signal transmission in wireless links with dispersive antennas, which are properly terminated to the transmitter and receiver front-ends. For this, a cascaded network model of the two-antenna channel based on the link decomposition theory [1] is employed to indicate practical conditions on maximizing gain-bandwidth product through selections of: i) real, dispersive antenna geometries; ii) their port terminations; and iii) assigned operational passbands. As a result, the gain-bandwidth product can be optimized for any given antenna geometry by appropriately specified terminal loads and operational bandwidths and vice-versa. This paper is numerically illustrated for canonical flat and solid dipole antennas by inspecting the predicted values of link gain-bandwidth products and related deviations of group delay used to measure signal distortions. [ABSTRACT FROM AUTHOR]

The frequency behavior of a bipolar operational amplifier (op amp) is always expected to worsen when the device is irradiated. In other words, parameters like the slew rate and the gain-bandwidth product are to decrease after either neutron or gamma tests. However, some neutron and TID tests performed on a large variety of bipolar op amps have shown that the evolution of the frequency behavior is not as simple as it is usually believed. In fact, there is evidence of an increasing influence of the power supply values on the former parameters, which can be extremely important in some devices. Also, the relationship among different frequency parameters has been investigated and, finally, an interesting and scarcely reported phenomenon is depicted. This phenomenon is the appearance of spontaneous oscillations in fed-back op amps, without doubt related to the modification of the gain and phase margins of the devices. [ABSTRACT FROM AUTHOR]

A transparent InAIAs/InGaAs superlattice (SL) multiplication layer at a wavelength of 1.55 µm was realized by using quantum effect. Using this SL, flip-chip separate absorption and multiplication InAIAs/InGaAs SL avalanche photodiodes with back-illuminated structure were demonstrated. A dark current lower than 2 µA at a multiplication factor of 10, a large gain-bandwidth product of 110 GHz, and a wide bandwidth of 12 GHz were obtained at the wavelength of 1.55 µm. [ABSTRACT FROM AUTHOR]

This article is concerned with the effect optical intensity has on the frequency response, gain, and bandwidth of the GaAs MESFET when used as an optical detector. Measurements show that the photoresponse gain can be increased by 10 dB as the optical intensity is lowered, while the bandwidth of the MESFET can be increased by an order of magnitude with an increase in optical power. [ABSTRACT FROM AUTHOR]

Interdigitated photoconductive detectors with 5-µm geometry have been fabricated on HEMT material and their optical response characteristics at 820 nm have been examined at DC and in the frequency range of 2-8 GHz. These have been compared with characteristics of similar 1-µm devices on MESFET material The shapes of the frequency responses were found to differ, but the useful bandwidth of both types of devices was found to be similar. [ABSTRACT FROM AUTHOR]