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16 February 1993 Theoretical limitations of broadband matching networks in PIN-FET receivers
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The sensitivity of PIN-FET-receivers can be improved if a matching network is used between the photodiode and the FET. Serial or parallel inductors as the simplest matching circuits are widely used in state-of-the-art receivers. This paper answers the question which performance can be achieved by an optimum infinite order matching network using only reactive (noise- free) passive elements. The highest signal-to-noise ratio at the output of an amplifier is achieved with noise matching at the input. It can be shown that for an FET noise matching is nearly equivalent to power matching. The fundamental works of Fano and Fielder on broadband power matching are applied to the matching problem between photodiode and FET. The result is a fundamental limitation on the transimpedance function for any matching network. The transimpedance function is defined as the ratio between the input voltage of the interior FET and the photocurrent. It can be concluded that a maximum bandwidth for a given transimpedance can be achieved if the transimpedance function is an ideal low-pass function. A trade-off between transimpedance and bandwidth is possible. In a numerical example, several novel low-pass structure matching networks were optimized with the result that the theoretical bound can almost be achieved. But even for high-order networks there is a ripple in the transimpedance function which cannot be reduced. It was found that networks with transmission lines show a performance always inferior to that of networks with lumped elements.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Andreas Czylwik "Theoretical limitations of broadband matching networks in PIN-FET receivers", Proc. SPIE 1788, Sources and Detectors for Fiber Communications, (16 February 1993);

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