Development of a CMOS 310-Mb/s receiver for free-space optical wireless links

12 This paper presents the design and implementation of a CMOS 310 Mb/s receiver for use in a multi-channel 155 Mb/s Manchester-coded optical wireless link. The receiver consists of a pre-amplifier followed by a post amplifier circuit. The pre-amplifier is a three stage transimpedance amplifier with an NMOS load at the output of each stage to control gain and stability. To allow the sensitivity of the performance to key parameters to be visualized a nomograph technique was developed. The contours of the nomograph show how DC bias, dominant pole frequency and the gain of each stage vary with transistor dimensions. This allows the designer to select transistor sizes for a given bit rate and for stable operation. The design has been optimized to achieve -30 dBm sensitivity at a BER of 10-9.