This paper demonstrates various designs of gigabit optical transimpedance amplifiers realized in sub-micron CMOS technologies. By exploiting current-mode circuit techniques such as common-gate and regulated cascade, the optimization of the design tradeoffs between gain and bandwidth in the transimpedance amplifiers is facilitated. Hence, the gain-bandwidth product performance is enhanced better than conventional voltage-mode optical receivers. Also, another current-mode transimpedance amplifier is introduced, which incorporates the current-mirror input configuration. Measured results of the proposed chips confirm the design methodologies and hence the benefits of the current-mode circuit designs for the applications of optical receivers.