Abstract: A digital automatic gain control device for use in a communication terminal of a mobile radio communication system employing a time-division duplex (TDD) transmission. A transmission power amplifier and a reception amplifier, which constitute the communication terminal, are fully composed of digital elements. In a transmission mode, a reception data latch is cleared to turn off the reception amplifier, so as to prevent a distortion of a modulated transmission signal due to regeneration and coupling of a modulated transmission waveform generated from a receiver. On the contrary, in a reception mode, a transmission data latch is cleared to prevent the carrier generated from the transmitter from being leaked toward a receiver, thereby preventing deterioration of a reception sensitivity of the receiver. Therefore, the transmission and reception gain can be accurately controlled based on the accurate timing control by the control processor.