Sharif Digital Repository

Gain-boosted cascode amplifiers are good choices for power optimiied high-speed amplifiers. In this paper, after a comprehensive study on the pole-zero locus and time response, a generic and perfect model is developed for these amplifiers. By the help of this novel modeling method, the optimum parameters for the feedback or auxiliary amplifier are determined, in order to eliminate the well-known slow timing component in the step response and obtain the minimum achievable senling time. The required circuit conditions as well as a straightforward design procedure for realizing the results of the analytic analysis are presented, finally. © 2003 IEEE  

We review our investigations on bismuth-oxide fiber as an amplifying medium for parametric amplifiers with continuous-wave pumping. The results lead to new applications in demultiplexing, which are discussed  

This paper presents the design and implementation of a bidirectional distributed amplifier (BDDA) in a 0.18- boldsymbol mu ext{m} CMOS process. The performance of the BDDA is theoretically analyzed, and the optimum number of gain stages ( n-{ ext {opt}} ), maximum achievable power gain ( G-{P} ), and circuit bandwidth are formulated. In addition, a new formula for proper choice of the number of DA stages (i.e., n ) is offered where dc-power consumption of the circuit ( P-{ ext {dc}} ) is also considered. This formula optimizes G-{P}/P-{ ext {dc}} , and it is preferred over the conventional n-{ ext {opt}} formula. To validate the theoretical analyses, a 2-12-GHz BDDA with high output 1-dB... 

Feed-forward is one of the main methods for linearization of microwave power amplifiers. Although the complexity of the system is increased, the level of inter-modulation rejection (IMR) of a feed-forward system can be improved using a multi-loop configuration. Predicting the IMR of such a system is of prime importance. A new analytical approach in modeling a multi-loop feed-forward system for predicting the linearization performance of the system is presented. The first loop of the multi-loop system is substituted by an equivalent amplifier model and then the reduced system as a new feed-forward system is evaluated. The predicted IMR values are verified using the ADS simulator and a MATLAB... 

A novel BiCMOS voltage-to-voltage converter with logarithmic characteristics and very high accuracy is presented. The relationship between the emitter current and the base-emitter voltage in bipolar transistors is used to realize the logarithmic function. With 1.8 supply voltage, the total power consumption is less than 15.75 mW and a Log error of < -36dB is shown in the ADS simulations. Compared to the other method in the literature, very better accuracy in logarithm calculation is achieved. The proposed method can be used in arithmetical operation circuits like analog processors  

A novel substrateless power amplifier module realized by ridge gap waveguide (RGW) technology is proposed in Ka-band. Up to our knowledge, this is the first time that an active device is directly integrated with an RGW structure. No substrate is used in the RF section of the implemented power amplifier and the whole structure is made by machining a piece of metal. The amplifier was made of two pieces and was easily assembled without needing a precise contact between the two sections. The cavity resonance of the amplifier is suppressed using a pining structure. The fabricated amplifier module is self-packaged and does not need any packaging. It is shown that the simulated and measured results... 

This paper presents a new high speed current mirror with continuous gain adjustment. Based on this current mirror, a variable gain current amplifier is designed in 0.18μm CMOS technology. The current gain of the amplifier can be continuously varied from 0 dB to 20 dB while the bandwidth of the circuit remains above 1.00 MHz. The circuit consumes 0.9 mW from 1.5V supply. © IEICE 2007  

The transformer-feedback (TRFB) interstage bandwidth enhancement technique for broadband multistage amplifiers is presented. Theory of the TRFB bandwidth enhancement and the design conditions for maximum bandwidth, maximally flat gain, and maximally flat group delay are provided. It is shown that the TRFB bandwidth enhancement can provide higher bandwidth compared to the conventional techniques based on reactive impedance matching networks. A three-stage low-noise amplifier (LNA) monolithic microwave integrated circuit with the TRFB between its consecutive stages is designed and implemented in a 0.1-μ m GaAs pHEMT process. The TRFB is realized by coupling between the drain bias lines of... 

An optical amplifier followed by a bistable element is statistically analyzed. To this end, the birth-death-immigration model and the coupled mode theory are used to characterize the amplifier and the bistable element, respectively  

The most challenging issue of conventional Time Amplifiers (TAs) is their limited Dynamic Range (DR). This paper presents a mathematical analysis to clarify principle of operation of conventional 2× TA's. The mathematical derivations release strength reduction of the current sources of the TA is the simplest way to increase DR. Besides, a new technique is presented to expand the Dynamic Range (DR) of conventional 2× TAs. Proposed technique employs current subtraction in place of changing strength of current sources using conventional gain compensation methods, which results in more stable gain over a wider DR. The TA is simulated using Spectre-rf in TSMC 0.18um COMS technology. DR of the 2×... 

This paper presents a bandwidth enhancement technique for broadband Darlington amplifiers. A detailed analysis of the high-frequency performance of the Darlington amplifier and the effect of bandwidth enhancement is provided. A design procedure is also given for broadband feedback Darlington amplifiers with bandwidth enhancement and gain flattening. A single- and a three-stage feedback amplifier with the proposed improvements are designed and implemented in a 0.25-μm Al-GaAs-InGaAs pHEMT technology. The single-stage amplifier provides 6 ± 0.4 dB of small-signal gain in the frequency band of 1-30 GHz. The three-stage amplifier features 17.8 ± 0.8 dB of small-signal gain in the frequency band... 

A CMOS fully differential UHF variable gain amplifier for use in a direct-conversion DVB-H receiver is presented employing input devices with variable aspect ratios. High linearity is achieved by reducing the transconductance of the input transistors for lower gain settings. It is shown that this technique has better linearity and noise performance compared to the conventional methods in which the gain reduction is performed at preceding stages. Implemented in TSMC 0.18-μm CMOS process, the inductorless RF VGA covers a voltage gain ranging from 15.5 dB to -6.5 dB with a maximum IIP3 of +24 dBm. The amplifier achieves a 3-dB bandwidth of 1.4 GHz and a minimum noise figure of 5.8 dB while... 

Design techniques to enhance bandwidth and linearity of broadband multistage low-noise amplifiers (LNAs) are presented. A feedback amplifier circuit is proposed to compensate for transistor gain roll-off with frequency in other amplifier stages and extend overall bandwidth. Moreover, a transistor width tapering in a multistage LNA is applied to improve linearity. These techniques are adopted in a three-stage monolithic microwave integrated circuit (MMIC) LNA implemented in a 0.1-μm GaAs pHEMT process. The LNA features 18-43 GHz bandwidth, 21.6 dB average gain, and 1.8-2.7 noise figure (NF). It exhibits output 1-dB compression point of 11.5 dBm at 30 GHz and consumes 70 mA bias current from a... 

This paper presents a methodology for the design of Ka/Q-band monolithic microwave integrated circuit (MMIC) high-power amplifiers (HPAs). Design techniques are introduced to reduce chip area and to improve bandwidth (BW). These techniques are applied to the design of a 31-39-GHz 5-W HPA implemented on a 0.1-μm AlGaAs-InGaAs pseudomorphic HEMT (pHEMT) technology. With chip dimensions of 3.35 × 3.2 mm2, the HPA achieves 24% average power-added efficiency (PAE) over the frequency band, while maintaining an average 22-dB small-signal gain. A balanced high-power amplifier (BPA) is also presented, which combines the power of two 5-W HPA cells to deliver peak 8.5-W output power (Pout) in the... 

Power amplifiers require linearization in order to reduce adjacent inter-modulation distortion without losing efficiency. Digital predistortion is a cost effective method to achieve this goal and it needs an accurate model of the amplifier. Most of the amplifier models are based on memoryless modeling. This kind of modeling is simple but it's not accurate enough if linearization is important; and also for wide band modulations like QAM, we should consider the memory effects of power amplifiers. © 2009 IEEE  

An Erbium-doped silica CROW can be employed as a band pass and band stop amplifier in telecommunication systems. Also it can be proposed as wide band amplifier as well as narrow band amplifier. We investigate theoretically and simulate structure of Erbium-doped CROW (EDC) with different parameters to realize its performance and possible applications as an amplifier. In this paper we try to consider effect of different parameters on gain spectrum of systems. © 2009 SPIE  

This paper presents a capacitor cross-coupled gm-boosting scheme for differential implementation of common-gate transimpedance amplifier (CG-TIA). A differential transimpedance amplifiers (DTIA) is designed by this scheme using two modified floating-biased CG stage with improved low corner frequency. Despite conventional methods for single-ended to differential conversion that increase the power and the noise for the same gain, the new DTIA gives a higher gain and hence reduces the input-referred noise power. Design of the DTIA circuit using 0.13 μm CMOS technology illustrates near 1.7 dB improvement in the circuit sensitivity and 5.2 dB enhancement in transimpedance gain compared to its...