一种用于高精度电流型DAC的输出级设计

Design of output circuit for high precision current-steering DAC

提出了一种应用于电流型数模转换器(DAC)的输出电路。在对输出级的功能和稳定性作了分析计算后,设计了一种高增益、低失真的运放(OP)电路。运放模拟的直流增益为108dB,环路带宽为30MHz,环路相位裕量为60度,在输出为1rms时,THD+N可达到104.8dB。和传统的开关电容(SC)输出级相比,该电路具有面积小、噪声低等优点,可应用于高精度的电流型DAC。

An output circuit used in current-steering digital to analog converter (DAC) is proposed. On the basis of analysis of the output stage function and stability, an operational amplifier (OP) with high gain and low distortion is designed. Simulation results of OP show that dc gain is 108dB, loop bandwidth is 30MHz, loop phase margin is 60 degree and THD+N is 104.8dB at 1rms output. Compared to the conventional switch capacity (SC) output stage, this output circuit has smaller area and lower noise, so it is a promising alternative in the high precision current-steering DAC.