Stability considerations and performance of wide dynamic range, ambient light active rejection circuits in photodiode receivers

We discuss several issues in active circuits for the rejection of ambient photocurrent over a wide dynamic range. These circuits are important for diffuse, free-space optical communications that operate over a variety of indoor and outdoor lighting conditions. In addition, we introduce, analyze and demonstrate a second-order rejection circuit based on a low noise gyrator in tandem with the input transimpedance amplifier. Excellent rejection is achieved over three orders of magnitude in ambient photocurrent. The measured transient performance agrees well with theory and simulations, and the rejection circuit was demonstrated with IrDA signals for outdoor applications in direct sunlight.