1、通用可变增益放大器通用可变增益放大器 摘摘 要要 本设计基于单片机的可变增益放大器设计，系统由前级输入缓冲模块、增益 控制模块，单片机控制模块，D/A 模块组成。采用 AT89S52 单片机作为微控制器， 以可编程增益放大器 AD603 为放大电路的核心。 设计具有通用可变增益放大及所 使用的基于单片机的直流电压源。由低噪声高速运放 OPA642 组成的前级缓冲电 路，波形无明显失真。由 AD603 级联组成增益放大器，实现增益 -2040dB 范 围内可按 4dB 步进可调，且在 06MHz 通频带内增益起伏在 1dB 以下，波形无明 显失真，采用的两级级联放大电路不但提高了放大增益而且扩展
2、了通频带宽。微 控制器由 AT89S52 单片机通过 8 位 D/A 转换芯片 DAC0832，再经运放芯片 LM324 输出，将数字信号转换成模拟电压信号，送增益放大器实现增益可调并经数码管 显示放大增益。 设计通过实验仿真完成。设计采用的压控增益器件 AD603，在进行了合理的 级联和阻抗匹配后，能进行增益的控制，稳定性好，可控范围大。整个设计除个 别指标未能达到设计要求外，其它全部达到设计要求。 关键字：可控增益放大；AD603；单片机 ABSTRACT The design of variable gain amplifier based on microcomputer, the s
3、ystem is consisted by the input buffer module, the gain control module, MCU control module, Using AT89S52 microcontroller as microcontrollers, programmable gain amplifier to amplifier AD603 as the core.Design is based on single chip microcomputer used by general variable gain amplifier and the dc vo
4、ltage source. Made up of low noise high-speed op-amp OPA642 front-end buffer circuit, waveform has no obvious distortion. By AD603 cascaded gain amplifier, the gain of -20 40dB range according to 4dB continuously adjustable, and in the 0 6MHz frequency pass band gain fluctuation in 0.5dB, waveform w
5、ithout significant distortion, using two cascaded amplification circuit can not only improve the amplifier gain and extends the frequency bandwidth. Micro controller is composed of AT89S52 microcontroller through the 8 bit D/A converter chip DAC0832, the chip LM324 output, converts digital signals i
6、nto analog voltage signal, send the gain of the amplifier gain can be adjusted and the digital tube display gain. Design through the experimental simulation is completed. Design of the VCO gain device AD603, carried out in a cascade and a reasonable impedance matching, control, can gain good stability, controllable range. The whole design in addition to individual indicators failed to meet the design requirements, other all meet the design requirements. Key words Controllable gain amplif
