12-bit 250-MHz digital transmitter with DAC and line driver

This paper proposes a 12-bit DAC using switched-current technique and segmented topology, which includes a 9-bit thermometer code and a 3-bit binary code and a 125-MHz fully differential current- mode line driver for a better noise immunity at high frequencies. High bandwidth and power reduction are the major factors of designing high-speed digital transmitter for over a decade. The main building blocks of digital transmitter are digital to analog converter and line driver. The main drawback of fully differential current-mode line driver is high power consumption. This problem can be nullified by synthesizing an output impedance with minimal output voltage drop and high power efficiency. Besides, the linearity of line driver is enhanced by using a current distribution circuit (CDC). The proposed line driver performs with an output voltage of ±1 VP, output current is ±10 mA, and the power consumption is 78 mW at the supply voltage of 1.8 V and the operating frequency of 125 MHz.