CMOS optical preamplifier design using graphical circuit analysis

grantor: University of TorontoNew requirements on optical receivers are being driven by the rapid expansion of optical communications beyond traditional fiber-optic links. This thesis discusses the design of transimpedance amplifiers that are used in the preamplifier stage of optical receivers. The three specific requirements that are addressed here are a wide dynamic range, ambient light rejection, and low-voltage operation. To achieve a wide dynamic range, we present a fully-differential, variable-gain CMOS transimpedance amplifier. The proposed topology is simpler than previous designs and has improved stability. The implemented design consumes 8mW at 3V, and provides 70 MHz bandwidth with a dynamic range of 77dB, a maximum transimpedance gain of 19k[Omega] and a gain range of 32dB. To reject ambient light, we place an active feedback loop around the transimpedance amplifier. This topology eliminates the need for large passive components and improves the regulation of the photodiode bias voltage. However, the lower-frequency limit of this topology is dependent on the ambient light level. We experimentally verify this technique, and analyze the stability requirements of the feedback loop. To achieve low-voltage operation, we develop a CMOS transimpedance amplifier capable of IV operation without the use of low-threshold MOS transistors. The design has a wide output swing and maximizes the available bias voltage for the photodiode. The biasing of the MOS feedback resistor is performed using a charge pump to generate a stable gate voltage--a technique called dynamic gate biasing (DGB). The proposed design was implemented as part of an optical receiver front-end which also included two post amplifiers. The resulting front-end consumes 1mW from a 1V supply and provides 210k[Omega] transimpedance gain over a 50MHz bandwidth. Also included in this thesis is the development and application of a graphical circuit analysis technique called DPI/SFG analysis that is based on driving-point impedances (DPI) and signal-flow graphs (SFG). We develop a general formulation of the technique, illustrate its use on a number of circuit examples, and apply it to the design and optimization of the low-voltage transimpedance amplifier.Ph.D

The impact of EMU on growth and employment

This study addresses and evaluates the impacts of the introduction of the euro on both actual and potential output and employment. In order to achieve this, a descriptive and analytical examination of developments before and after the launch of the euro is undertaken, with comparisons drawn between countries that are EMU members and non-EMU members. There are several channels through which the euro may have affected growth and employment: greater transparency and its impact on competitiveness and the effectiveness of the single market; integration of financial markets, which may raise productivity; and a more stable macroeconomic environment, which affects risk and investment decisions. We analyse the impact of each of these channels on the drivers of growth, after controlling for factors such as workforce skills, research base, openness, demographic developments and structural reform on the evolution of output. The central result of our study is that EMU affects output growth directly and also promotes reductions in output and real effective exchange rate volatility and thereby influences the accumulation of productive capital. Many potential concerns preceding the launch of the euro seem to have been unfounded, and our work suggests that the effects of EMU that we observe have been beneficial for economic growth and employment overall. Our analysis suggests that the direct positive effects of EMU are likely to be larger in the core countries, despite their recent slow growth, and that EMU may lead to agglomeration of activities