无共模反馈电路的低功耗可变增益放大器

Low-Power Variable Gain Amplifier Free of Common-Mode Feedback Circuit

设计了一种低功耗高动态范围数字控制的可变增益放大器。提出了一种新的稳定输出共模电平的方法,在负载电阻切换的同时改变流过电阻中的电流来保持电阻上的电压降不变,从而稳定输出共模电平。该方法无需额外的共模反馈电路,降低了功耗。同时采用级间电容耦合结构解决了直流失调问题,不需要直流失调校准电路。采用TSMC 0.18μm CMOS工艺进行了电路设计和仿真。仿真结果表明,该可变增益放大器消耗的平均电流为504.7?A,?3 dB带宽大于1.16 MHz,动态范围达到了81 dB,变化步长为3 dB,增益误差小于±0.65 dB。

A low-power high-dynamic range digitally controlled variable gain amplifier （VGA） is designed in this paper. First, a novel method for defining the output common-mode voltages of VGA is proposed by adjusting the current of the load resistor according to the change of its resistance to keep the voltage drop across the load resistor unchanged, so that the common-mode feedback circuit is not required for the VGA, resulting in decreased power consumption. Second, coupling capacitors are used between the stages to remove the DC offset, and hence no extra DC offset cancellation circuit is necessary. The VGA is designed and simulated in TSMC 0.18 μm CMOS process. Simulation results show that, the VGA dissipates an average current of 504.7 μA while achieving 1.16 MHz -3 dB bandwidth and providing 81 dB gain range with 3 dB resolution, and the gain error is less than -0.65 dB.