A Fully-Integrated Optoelectronic Detector With High Gain Bandwidth Product

An optoelectronic circuit integrated with a photodiode is proposed, which simultaneously achieves 3.5-MΩ transimpedance gain and 18-MHz bandwidth. The design is intended to address the limits on bandwidth introduced by the large parasitic capacitance of the integrated photodiodes in optoelectronic applications. The proposed circuit consists of a transimpedance amplifier (TIA) and a voltage gain stage. The pre-stage TIA with low input impedance provides the main transimpedance gain of the circuit over a wide bandwidth. The post voltage gain stage provides the supplemental voltage gain for the circuit and increases its driving capability. The circuit is fabricated in a 0.5-μm CMOS process with an active area of 501.2 μm × 291.6 μm. When the light input is a 100-ns pulse with 905-nm wavelength and 1.5-μW optical power, the amplitude of output signal is 1.6 V with a rise time of 24.5 ns and a delay time of 21 ns.