A comparative analysis of implementations of an optical front-end with variable transimpedance intended for optical storage systems in two different BiCMOS technologies is given in this article. The variable-gain current amplifier within the optical front-end is designed by using a modified balanced type of the bipolar junction transistors translinear loop. The predictions of the optical front-end mathematical models are confirmed by the measured results. They show that a 0.6-mm BiCMOS silicon technology implementation with worse bipolar junction transistor parameters (unity-gain frequency, current gain b, and the Early voltage) gives much better stability than a 0.35-mm BiCMOS silicon-germanium technology implementation. As a consequence, the useful measured transimpedance dynamic range of the proposed optical front-end is 17.5 times larger in the 0.6-mm BiCMOS silicon technology than that in the 0.35-mm BiCMOS silicon-germanium technology.
A 0.35 lm SiGe BiCMOS optical receiver with voltage-controlled transimpedance is presented. A variable-gain current amplifier using a BJT translinear loop is applied. A transimpedance dynamic range of 1554 (63.8 dB) with the largest transimpedance of 2.84 MX, a bandwidth up to 379 MHz, and a transimpedance bandwidth product up to 168 TXHz are achieved.
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