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采用全差分运算放大器、无源电阻以及用作可变电阻的MOS管设计实现了全差分R MOSFET C四阶Bessel有源低通滤波器 ,在所提出的电路中通过调节工作在线性区的MOS管有源电阻的阻值以抵消集成电路制造工艺过程中电阻阻值的一致性偏差 ,达到Bessel滤波器的群时延值得到精确设计的目的 .该滤波器中所采用的全差分运算放大器不仅具备有电压共模负反馈 ,而且还具有电流共模负反馈 ,极有利于电路静态工作点的稳定 .通过无源双端RLC原型低通滤波器导出的 0 75μs群时延四阶Bessel滤波器 ,采用台湾联电 (UMC) 2层多晶硅、2层金属 (2P2M )、5 0V电源电压、0 5μmCMOS工艺制造 ,在输入信号为 1 0 0kHz、2 5Vpp时 ,其谐波失真 (THD)值低于- 65dB .
Fully differential R MOSFET C fourth-order Bessel active low-pass filter with fully differential op amp, passive resistor and MOS tube used as a variable resistor. In the proposed circuit by adjusting the MOS The resistance value of the active resistance of the transistor is used to offset the uniformity deviation of the resistance value in the manufacturing process of the integrated circuit so that the group delay value of the Bessel filter can be accurately designed. The fully differential operational amplifier used in the filter not only With voltage common-mode negative feedback, but also with current common-mode negative feedback, is very conducive to the stability of the circuit static operating point. Passive double-ended RLC prototype low-pass filter derived 0 75μs group delay fourth-order Bessel filter , Manufactured by UMC’s 2-layer polysilicon, 2-layer metal (2P2M), 50V supply voltage and 0 5μm CMOS process. The harmonic distortion (THD) value is lower when the input signal is 100kHz and 2 5Vpp - 65dB.