增益连续可调宽带前置放大电路设计与实现

Design and realization of a wide-band pre-amplifier circuit with continuous and adjustable gain

针对数字示波表等仪器对前置通道的高性能要求,文中采用程控增益运算放大器作为核心器件,设计并实现了一种宽带前置放大电路。采用单片J-FET型宽带运放作为电路的输入级,与传统设计方法相比,在提高输入阻抗同时简化了电路结构。采用高精度数模转换器控制程控增益运算放大器灵活地实现了信号的放大功能。实验结果表明,所设计的放大电路工作稳定可靠,其-3dB带宽在各个量程下均高于120MHz,增益在-50dB到40dB范围内连续可调。

Aiming at the high requirement of the input channel for instrument such as digital scopemeter,this paper designs and realizes a wide-band pre-amplifier circuit,employing a gain-programmable operational amplifier as the core device.It adopts a single integrated operational amplifier of J-FET type to act as the input stage of the circuit.Comparing with the traditional design method,the proposed method simplifies the structure of circuit while increasing the input impedance.It utilizes a high-precision digital-to-analog converter to control the gain-programmable amplifier and realizes a versatile amplification function.The experimental results show that the amplifier can operate stably,the-3dB bandwidth of the whole circuit under each gain surpasses 120MHz,and the gain in the span of-50dB to 40dB can be changed continuously.