This paper proposes a signal processing methodology of communication system and realized that circuits using operational transconductance amplifier (OTA). Two important classes of communication circuit, delta modulator and compander have been designed using that procedure. In the first implementation coded pulse modulation system is demonstrated which employ sampling, quantizing and coding to convert analog waveforms to digital signals while the second gives data compression and expansion in digital communication system. The proposed compander circuit is realized with operational transconductance amplifier and diode. Required power supply to operate the circuit is 3.5V. Performance of the circuits realized with OTAs has been demonstrated through SPICE simulation.