Inductive-peaking-based bandwidth extension techniques for CMOS amplifiers in wireless and wireline applications are presented. To overcome the conventional limits on bandwidth extension ratios, these techniques augment inductive peaking using capacitive splitting and magnetic coupling. It is shown that a critical design constraint for optimum bandwidth extension is the ratio of the drain capacitance of the driver transistor to the load capacitance. This, in turn, recommends the use of different techniques for different capacitance ratios. Prototype wideband amplifiers in 0.18-m CMOS are presented that achieve a measured bandwidth extension ratio up to 4.1 and simultaneously maintain high gain ( 12 dB) in a single stage. Even higher enhancement ratios are shown through the introduction of a modified series-peaking technique combined with staggering techniques. Ultra-wideband low-noise amplifiers in 0.18-m CMOS are presented that exhibit bandwidth extension ratios up to 4.9.
As we are surrounded by an ever-larger variety of post-PC devices, the traditional methods for identifying and authenticating users have become cumbersome and time-consuming. In this paper, we present a capacitive communication method through which a device can recognize who is interacting with it. This method exploits the capacitive touchscreens, which are now used in laptops, phones, and tablets, as a signal receiver. The signal that identifies the user can be generated by a small transmitter embedded into a ring, watch, or other artifact carried on the human body. We explore two example system designs with a low-power continuous transmitter that communicates through the skin and a signet ring that needs to be touched to the screen. Experiments with our prototype transmitter and tablet receiver show that capacitive communication through a touchscreen is possible, even without hardware or firmware modifications on a receiver. This latter approach imposes severe limits on the data rate, but the rate is sufficient for differentiating users in multiplayer tablet games or parental control applications. Controlled experiments with a signal generator also indicate that future designs may be able to achieve datarates that are useful for providing less obtrusive authentication with similar assurance as PIN codes or swipe patterns commonly used on smartphones today.
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