Paper Title
DC Biased Differential Photocurrent Sensing Input Stage for Visible Light Communications

The reverse bias voltage across the PIN photodiode is essential for the photodiode to operate in the photoconductive mode. This paper presents an input bias structure with differential photocurrent sensing suitable for VLC front-ends. The photodiode bias voltage is provided by two opposite common-collector (CC) DC level shift input stages. The amount of bias voltage could be optimised according to the photodiode required sensitivity and capacitance. The differential configuration makes the transimpedance amplifier immune to any common mode noise. The proposed method is applied to ahypothetical transimpedance amplifier and results are compared with single ended structure. Simulation results showed that using this approach it is possible to achieve a transimpedance gain of 120 dBΩ over a maximum bandwidth of 14.5 MHz with a common mode rejection ratio of 61 dB while the circuit provides a controlled bias voltage of up to 6 V across the PIN photodiode. Index Terms - Positive-Intrinsic-Negative (PIN), transimpedance amplifier (TIA), visible light communications (VLC).