一种用于宽带中频滤波器的运算放大器共模补偿方法

A Common Mode Compensation Method of Operational Amplifier for Wideband IF Filter

介绍了一种适用于宽带中频(IF)滤波器的运算放大器共模补偿方法,并将其应用于较大带宽有源RC滤波器中,如宽带宽接收机中频的电路和高频模数转换器抗混叠滤波器等。运算放大器通过前馈方式补偿共模次极点,并根据寄生电容调整前馈跨导电流比例来配置零点位置。该方法在一定功耗和较大共模带宽要求下,保证了共模反馈的开环相位裕度。将该方法应用于6阶复数/IQ低通切比雪夫滤波器中并采用130 nm CMOS工艺进行流片。测试结果表明,上述滤波器在最大带宽40 MHz、核心电源电压1.2 V下,滤波器最大功耗为24.6 mW,40 MHz低通配置时其中心频率处等效输入噪声电压为35nV/√Hz,等效输入三阶交调点为30 dBm。

A common mode compensation method of operational amplifier for wideband intermediate frequency(IF)filter was introduced,which was applied to the active RC filter with large bandwidth,such as the IF circuit of wide bandwidth receiver and anti-aliasing filter of high frequency analog-to-digital converter.The operational amplifier compensated common-mode non-dominate poles through feedforward mode,and configured its zero position by adjusting the feedforward transconductance current ratio accor-ding to the parasitic capacitance.The method guaranteed the open-loop phase margin of common mode feedback under certain power consumption and large common mode bandwidth requirements.The method was applied to a 6-order complex/IQ low-pass Chebyshev filter which was fabricated in 130 nm CMOS process.The test results show that the maximum power consumption of the filter is 24.6 mW under the maximum bandwidth of 40 MHz and the core supply voltage of 1.2 V.The equivalent input noise voltage at the center frequency is■and the equivalent input third-order intercept point is 30 dBm under 40 MHz low-pass configuration.