Design Of Optical Receiver Preamplifier Based On Standard CMOS Technology

In recent years, it is urgent to build an information super-highway with rapid development of telecommunication networks, computer networks and internet. Undoubtedly, optical communications has merits such as large capacity, long transmit distance, economizing energy source, anti-interference and anti-radiation and so on. So it has become the mainstream technology of the information super-highway. Unfortunately, the chips almost all rely on imports in this area. Therefore, it is very important to design high speed integrated circuits for transmission systems with independent property.Optical receiver is a most important part in the optical fiber communication system. Its main function is to transform the weak light signal passed from optical fiber into electrical signal. After enlargement, it can return to original signal. As a critical part of the optical receiver, the function of the preamplifier is a weak current signal is converted into a voltage signal and a certain amount of amplification, and then lost to the main amplifier. Therefore, its performance has a great effect on the optical receiver.The thesis is based on0.18μm CMOS technology, which designs a RGC input trans-impedance preamplifier with AGC function of optical receiver. The input stage of this amplifier with RGC configuration, broadened the bandwidth, improved trans-impedance effectively. Used voltage shunt negative feedback structure, embedded AGC technology at gain stage, in addition to expanded the input dynamic range, also played a role improve the trans-impedance and reduce noise. In order to achieve single-ended preamplifier output signal can adapt to the follow-up of the main amplifier double-ended input, a single-ended-to-differential circuit in the output stage design.Simulation results show that when input of the optical power of-10dBm, the power supply voltage is1.8V, and the parasitic capacitance CD of the diode for a typical0.5pF. The trans-impedance gain of preamplifier is81dBΩ,-3dB bandwidth is 2.25GHz, the average noise current spectral density approximately is6.0pA/Hz1/2, the light sensitivity is-20dBm, input resistance is50Ω, internal power dissipation only is58mV. Compared to conventional trans-impedance preamplifier, the design of the bandwidth, gain, sensitivity and power consumption performance have been improved to varying degrees.