基于JFET的高精度可程控放大电路设计  

Design of High-precision Programmable Gain Amplifier Based on JFET

作　　者：刘红俐[1] 李辉[2] 朱其新[2] 杨辉[2] 

机构地区：[1]华东交通大学基础科学学院,南昌330013 [2]华东交通大学电气与电子工程学院,南昌330013

出　　处：《自动化与仪表》2010年第7期42-46,共5页Automation & Instrumentation

基　　金：科技部863项目(2008AA04Z129);国家自然科学基金项目(60964004;60864004;60804066;60904049);浙江省科技厅新苗人才计划项目(2008R40G2030045);江西省自然科学基金项目(2009GZS0014);江西省教育厅资助科研项目(GJJ10456)

摘　　要：微弱信号常常伴随大量的噪声且驱动能力较弱,给精确测量带来很大难度。基于结型场效应管的程控放大器以压控放大电路为核心,通过单片机C8051F020控制12位D/A输出,改变工作在可变电阻区的结型场效应管的栅极电压以改变反馈电阻,从而实现放大倍数精确调节,使整个系统操作起来更加简单、方便。系统实现对信号1到1000倍放大并可程控,通过液晶显示输入、输出值和放大倍数。测试结果显示系统能够对最小1mv的输入信号进行预定放大且具有较高的精度;以JFET为核心的压控电阻工作速度快、可靠性好、控制灵敏度高,无机械触点使其噪声较低;系统12位A/D、D/A均集成在单片机内部,缩减了复杂的外围电路,可靠性高;系统还具有输入电阻大、共模抑制比高等特点。因此在数据采集系统、自动增益控制、动态范围扩展、远程仪表测试等微弱信号测量方面使用尤为适宜。Accurate measurement of weak signal is difficult because of its attentant noise and its weak drive capability.Program-controlled amplifier,based on JFET and with voltage-controlled circuit as its core,controls the output of 12-bit D/A by C8051F020 and can increase magnification precision adjustment by changing the gate voltage of JFET ’s feedback resistor in variable resistor area,and then the whole system becomes simple and convenient.Through system,signals can be amplified 1 to 1000 times and amplification can be programmed.LCD is used to display input,output value and the magnification.Results show that 1mv minimum input signal is able to be amplified with high precision.The voltage-controlled resistor has high speed,good reliability and high sensitivity of coercion.It also has low noise because of non-mechanical contact.12-bit A/D,D/A are integrated in the microcontroller,which reduces the complexity of the peripheral circuits and improves reliability.High common-mode rejection ratio（CMRR）is also a benefit of the system.Therefore,the system is particularly suitable in weak signal measurements,such as data acquisition systems,automatic gain controlling,dynamic range expansion,remote meter testing and so on.

关 键 词：压控电阻 结型场效应管 高精度 程控 低噪声 

分 类 号：TP273[自动化与计算机技术—检测技术与自动化装置]