An intermediate frequency (IF) variable gain amplifier (VGA) with exponential gain control for a radio receiver is fabricated in 0.25-μm CMOS technology. The techniques to improve the bandwidth and to reduce temperature dependence of gain are described. The complete VGA is composed of two stages of linearized transconductance VGA and three stages of fixed gain amplifier (FGA). The complete VGA ...

into the effective operation of variable gain amplifiers (VGA) in automatic gain control (AGC) applications. Figure 1 is a general block diagram for an AGC loop. The input signal passes through the VGA to produce the output level to be stabilized. The detector’s output is compared against a setpoint voltage to produce an error signal, which is then integrated to produce a gain control voltage. ...

A large dynamic-range Variable Gain Amplifier (VGA) suitable for Ultra Wide Band (UWB) applications is presented. The VGA is composed of three programmable variable gain amplifier stages followed by an output buffer. Such wide bandwidth allows our proposed VGA to be used in multi-standard protocols. Power reduction is developed for the variable gain amplifier stages. Thorough analyses of the mi...

This paper presents a low-power linear variable gain amplifier (VGA). This VGA gains its low-power linear properties with the help of the local feedback auxiliary (LFA) amplifier. The core of this LFA amplifier is based on flipped voltage follower (FVF) circuit. This VGA provides the flexibility to tune its gain with dual tuning voltages. Gain range of 15 dB to 16 dB with maximum bandwidth of 2...

We have investigated native defects and native defect-impurity complexes as candidate sources for the yellow luminescence in GaN. Using state-of-the-art first-principles calculations, we find strong evidence that the Ga vacancy (VGa) is responsible. The dependence of the VGa formation energy on Fermi level explains why the yellow luminescence is observed only in n-type GaN. The VGa defect level...

Since the physical topology of Mobile Ad hoc Networks (MANETs) is generally unstable, an appealing approach is the construction of a stable and robust virtual topology or backbone. A virtual backbone can play important roles related to routing and connectivity management. In this paper, the problem of providing such a virtual backbone with low overhead is investigated. In particular, we propose...

The Vga and Msr resistance determinants, encoded by mobile genetic elements in various staphylococcal strains, belong to a family of ATP-binding cassette (ABC) proteins whose functions and structures are ill defined. Their amino acid sequences are similar to those of proteins involved in the immunity of streptomycetes to the macrolide-lincosamide-streptogramin antibiotics that they produce. Seq...

We found a new variant of the streptogramin A resistance gene, vga(A)LC, in clinical isolates of Staphylococcus haemolyticus resistant to lincomycin and clindamycin but susceptible to erythromycin and in which no relevant lincosamide resistance gene was detected. The gene vga(A)LC, differing from the gene vga(A) at the protein level by seven amino acid substitutions, was present exclusively in ...

The effects of H on the interaction between Ga vacancies VGa and N in GaAs12xNx dilute alloys are studied through first-principles total-energy calculations. We find that N binds to Ga vacancies and that in the presence of H this binding is enhanced. The formation energy of VGa bonded to N and H ~resulting in a N-H-VGa complex! can be more than 2 eV lower than that of the isolated Ga vacancy VG...