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设计了一款适用于集成热真空传感器的二阶1位Σ-Δ调制器。该调制器采用前馈通道抑制积分器的输出摆幅、降低谐波失真、提高动态范围。为了降低运算放大器的1/f噪声,积分器中引入相关双采样电路。利用Matlab/Simulink,分析运算放大器的非理想性对调制器性能的影响。调制器由全差分开关电容电路实现。仿真结果表明:在4 MHz采样频率和6.8 kHz信号输入频率-3、dBFS幅值下,电路的最大信噪比为86.9 dB,分辨率可达14位。调制器的有效面积为0.67 mm2。3 V电源电压供电时,功耗为12 mW,各项性能指标均满足设计要求。
A second-order 1-bit sigma-delta modulator is designed for integrated thermal vacuum sensors. The modulator uses a feedforward channel to suppress the output swing of the integrator, reducing harmonic distortion and improving dynamic range. In order to reduce the 1 / f noise of the op amp, the correlated double sampling circuit is introduced into the integrator. Using Matlab / Simulink, the influence of the nonideality of the op amp on the performance of the modulator is analyzed. The modulator is implemented by a fully differential switched capacitor circuit. The simulation results show that the maximum signal-to-noise ratio of the circuit is 86.9 dB and the resolution is up to 14 bits at 4 MHz sampling frequency and 6.8 kHz input frequency -3 dBFS amplitude. The effective area of the modulator is 0.67 mm2. Power dissipation of 12 mW at a supply voltage of 3 V supplies meets all design requirements.