A circuit for implementing an operational transconductance amplifier (OTA) based on telescopic topology, wherein cascode transistors of the operational transconductance amplifier (OTA) are self-biased without using additional biasing circuitry, which not only reduces power consumption but also achieves high gain without extra current, and each cascode stage of the OTA has a pair of transistors so that the swing of the output differential signals of the OTA can be completely symmetrical so as to benefit second-order harmonic rejection, CMRR and PSRR.