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This paper presents an inverter-based active feedback transimpedance amplifier (IAF-TIA), in which an active feedback is applied to a voltage-mode inverter-based TIA, and therefore, the controlled positive regeneration process enables the proposed IAF-TIA to achieve the limiting operations for input currents greater than 100 μApp. However, the active inverter feedback mechanism might be prone to instability, hence mandating a very careful optimization of the loop gain. For this purpose, a diode-connected NMOS transistor is employed as a switch in the feedback path with its gate connected to the input, which helps not only to mitigate the corresponding issue but also to accommodate large input currents up to 1.5 mApp. The proposed IAF-TIA implemented in a standard 180 nm CMOS process demonstrates a 70.5 dBΩ transimpedance gain, 1.21 GHz bandwidth, 4.3   pA / Hz noise current spectral density, 63.5 dB input dynamic range, and 23.6 mW power dissipation from a single 1.8 V supply. The chip core occupies an area of 180 × 50 μm2, including an on-chip P+/N-well/Deep N-well avalanche photodiode as an optical detector. [ABSTRACT FROM AUTHOR]

In this article the authors presents an optimal defensive system for information technology (IT) security for a university network. By using this model, the system security expense from can be cut down to half. At the same time, this model is flexible enough to adapt to changing technological capabilities and can be applied to different organizations. Risks to IT security can be broken down into the three categories of confidentiality, integrity, and availability; hence, we face a problem in multiple-objective programming. Risk evaluation is very complex; there are not only quantitative standards of evaluation, but also qualitative standards that are difficult to measure. Defensive measures include technologies and policies. Technologies are hardware and software installed to protect the network, policies are guidelines publicized to instruct users' activities. Technologies should be different in each subsystem, according to the function it realizes, but policies should be the same throughout the whole network system.