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采用电压控制的伪电阻结构,设计了一款具有超低频下截止频率调节功能的带通可变增益放大器(VGA),由于该结构具有可调节超大的等效电阻和反馈电容使VGA的下截止频率可以调节。提出了一种改进的甲乙类运算跨导放大器(OTA)结构,采用新颖的浮动偏置设计,在满足高压摆率的条件下,有效提高共源共栅结构的电压输出范围。将伪电阻用于OTA的共模反馈,克服了阻性共模检测结构负载效应的问题。该VGA电路采用TSMC 0.18μm标准工艺设计和流片,测试结果表明,1.2 V电源电压下,其下截止频率调节范围为1.3~244 Hz,增益为49.2,44.2,39.2 d B,带宽为3.4,3.9,4.4 k Hz,消耗电流为3.9μA,共模抑制比达75.2 d B。
A voltage-controlled pseudo-resistance structure is adopted to design a band-pass variable gain amplifier (VGA) with a cutoff frequency adjustment function at ultra-low frequency. Because of its adjustable oversized equivalent resistance and feedback capacitance, Frequency can be adjusted. An improved Class A and B Transconductance Amplifier (OTA) structure is proposed. The novel floating bias design can effectively improve the voltage output range of the cascode structure under the condition of high slew rate. The pseudo-resistors are used for OTA common-mode feedback to overcome the problem of resistive common-mode detection structure load effect. The VGA circuit uses TSMC 0.18μm standard process design and flow sheet, the test results show that under the 1.2 V supply voltage, the next cut-off frequency adjustment range of 1.3 ~ 244 Hz, gain of 49.2,44.2,39.2 d B, a bandwidth of 3.4, 3.9,4.4 k Hz, the current consumption of 3.9μA, common mode rejection ratio of 75.2dB.