CMOS limiting optical preamplifiers using dynamic biasing for wide dynamic range

This paper presents limiting techniques for improving the dynamic range of CMOS optical preamplifiers while minimizing power dissipation. A fully-differential transimpedance amplifier using diodes clamps to limit output voltage is analyzed. A design with a transimpedance gain of 5 kΩ and total bias current of 2.9 mA is simulated to handle a maximum photocurrent of 400 μA at 100 Mbps, with an input-referred noise of 177 nA(rms). Dynamic biasing techniques are then introduced to improve dynamic range. A Class A topology is simulated to double maximum photocurrent at similar power, gain, speed and noise parameters, while a Class AB topology is shown to handle a maximum photocurrent of 1.5 mA.