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一种高频正反馈带通放大电路的设计

Design of a High-frequency Positive-feedback Bandpass Amplifiers

  • 摘要: 目前光量子噪声探测器的探测频率普遍较低,为使其能够在高频处测量光场的量子噪声,提出一种高频正反馈有源带通放大电路的设计方案。基于正反馈带通放大电路结构推导出放大电路的传递函数,得到放大电路谐振频率、Q值、增益3个特征参数的表达式;以中心频率为80 MHz、带宽为3 MHz、增益为200的电路设计为例,根据3个特征参数表达式确定放大电路中电阻、电容等参数,且采用Multisim软件仿真验证了理论分析和设计方案的正确性。以高速、低噪声运算放大器OPA847为核心,按设计参数搭建正反馈带通放大电路,对其工作性能进行测试。结果表明:按设计方案搭建的电路,中心频率为80 MHz、带宽为2 MHz、增益为14 dB,中心频率、带宽、增益的实验结果与设计值吻合较好,少许误差来源于运算放大器本身的阻抗、实际电路中阻值偏差及电路板的分布电容和电感等。采用本文设计方案确定放大电路中电阻、电容参数可在不影响放大电路中心频率的情况下调节增益,使探测器达到高频、窄带、高增益的效果。

     

    Abstract: At present, the detection frequency of optical quantum noise detectors is generally low. In order to enable the detector to measure the quantum noise of light field at high frequencies, a design scheme of high frequency positive feedback active band-pass amplifier circuit was proposed. The transfer function of the amplifier circuit was derived from the circuit structure, and the expressions of the resonant frequency, Q value and gain of the amplifier circuit were obtained. Taking the circuit design with a center frequency of 80 MHz, a bandwidth of 3 MHz and a gain of 200 as an example, the resistance, capacitance and other parameters in the amplifier circuit were determined according to three characteristic parameter expressions, and the correctness of the theoretical analysis and design scheme was verified by using Multisim software simulation. Based on the high-speed and low-noise operational amplifier OPA847, a positive feedback band-pass amplifier circuit was built according to the design parameters, and its working performance was tested. The results show that the circuit built according to the design scheme has a center frequency of 80 MHz, a bandwidth of 2 MHz, and a gain of 14 dB. The experimental results of the center frequency, bandwidth, and gain are in good agreement with the design values. A little error comes from the impedance of the operational amplifier itself, the resistance value deviation in the actual circuit, and the distributed capacitance and inductance of the circuit board.Using this design scheme to determine the parameters of resistance and capacitance in the amplifier circuit, the gain can be adjusted without affecting the central frequency of the amplifier circuit, so that the detector can achieve the effect of high frequency, narrow band and high gain.

     

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