一种斩波稳定低噪声Σ-Δ调制器设计

Design of a Chopper Stabilized Low Noise Σ-Δ Modulator

针对Σ-Δ调制器输入失调电压的需求,设计了一种新型低输入失调电压的Σ-Δ调制器。利用斩波稳定运算放大器和新颖的开关电容积分器,动态消除了直流失调电压以及低频噪声(主要包含1/f噪声),使得调制器的输入失调电压微乎其微。基于0.15μm CMOS工艺,利用Hspice软件对电路进行仿真,同时采用Matlab和TCL对仿真结果进行分析。仿真结果表明,在电源电压为4.5～5.5 V、温度为-40℃～85℃、各种工艺角下,低频噪声抑制能力增加了15 dB,且当运算跨导放大器的失调电压为10 mV时,Σ-Δ调制器的输入失调电压由9.7 mV下降为0.4 mV。

For the strict requirements ofΣ-Δmodulator’s input offset voltage,a newΣ-Δmodulator with a low input offset voltage was presented.To get a low input offset voltage modulator,the DC input offset voltage and the low frequency noise(mainly including 1/f noise)were cancelled dynamically by using a chopper-stabilized amplifier and a novel switched-capacitor integrator.The proposed offset voltage cancellation scheme was explained and derived in theory.Finally,based on a 0.15μm CMOS process,Hspice was used to simulate the circuit.Meanwhile Matlab and TCL were used to analyze the simulation data.Simulation results showed that,at a supply voltage range of 4.5~5.5 V and a temperature range of-40℃~85℃,and in all process corners,the low frequency noise of output was improved by about 15 dB.When the offset voltage of the operational transconductance amplifier was 10 mV,the input offset voltage of the proposedΣ-Δmodulator was reduced from 9.7 mV to about 0.4 mV.