A Comparison between Three GaAs Monolithic Transimpedance Amplifiers for Optical Communication Systems

Three different GaAs Monolithic Transimpedance Amplifier topologies for low noise and high speed optical communication systems are compared. The first one consists of a simple cascode stage enhanced in terms of bandwidth and noise. The second one is also based in a cascode stage followed by a differential amplifier in order to increase the transimpedance gain-bandwidth product. The third one was designed with that same scope in one hand and in the other to obtain a very low power consumption; it consists of a three stage inverter amplifier with reactive feedback loop. Measurements show that excellent results have been obtained for the first topology; for the second one a remarkable improvement of the bandwidth has been obtained; finally, for the third one, high gain and extremely low power consumption have been obtained. In all cases the equivalent noise current is low enough to achieve a sensitivity of the receiver between -28 and -33 dBm.