半导体探测器输出电流检测系统前置放大器设计

为满足半导体探测器输出电流检测系统的需求,设计了与之相适应的前置放大器。该前置放大器基于超低偏置电流运放ADA4530,采用单个反馈电阻和T型反馈网络的I/V变换前置放大电路组成。测试结果表明:该前置放大器的放大倍数可达10 mV/pA,直流偏移为8μV;对于pA级分辨率,其输出噪声电压频谱密度仅为17.75 nV/(Hz)~(1/2),输出总噪声为409μV;可用于μA~pA范围内的核辐射探测器电流信号测量。     

微弱电流I-V转换电路保护环设计

针对微弱信号电路易受干扰和输入端泄漏电流影响测量精度问题,对电路进行了保护环的设计。该电路分别采用T型反馈电阻网络和单个大电阻反馈网络,选择输入电阻足够大、偏置电流小的运算放大器进行设计。EMI仿真和实验结果都表明保护环的引入提高了电路的抗干扰性,从而显著地提升了电路的灵敏度、测量的精度和稳定性。     

直流微电流前置放大器的研究

介绍了一种直流微电流放大器的设计,先通过原理分析,指出应重点注意的一些关键性问题及提高信噪比的途径.并以此设计了实用电路,给出测试方法及测试数据.该放大器具有分辨率高、响应快、漂移低、稳定性好以及价格低廉等优点,非常适合光电流、生物电流及射线电流测量.     

一种基于电流反馈芯片的电荷灵敏快前放设计

介绍了一种基于电流反馈运算放大器(CFOA)的快电荷灵敏放大电路。通过一个小电阻的引入避免了CFOA电路直接电容反馈所引起的电路不稳定问题,通过反馈电阻和反馈电容的适当取值降低了噪声。经过测试,其带宽可达200MHz,时间分辨率可达125ps。该前放具有高带宽、高性噪比、高时间分辨率等特点,已成功应用于兰州重离子加速器单粒子效应地面模拟实验TR5终端。     

基于阻容低通反馈的电荷灵敏前置放大器的设计

传统电荷灵敏前置放大器以高阻值电阻作为低频反馈端,高阻值电阻所引入的热噪声为前置放大器噪声的主要来源。本文以N沟道结型场效应晶体管和阻容(Resistor-Capacitance,RC)电路构成低通网络代替传统高阻值反馈电阻完成了新型电荷灵敏前置放大器的研制。该电路以结型场效应晶体管和集成运算放大器构成放大电路,具有高输入阻抗及大开环增益的优点;以小容值电容构成高通回路,为电路提供高频反馈回路,同时实现核脉冲电流的积分;以RC低通网络构成直流反馈回路,为电路提供一个稳定的直流工作点,同时构成电压分压器使N沟道结型场效应管工作在正向偏置状态,实现对反馈电容中的电荷进行连续放电。相比于传统阻容反馈式电荷灵敏放大器,该电路能够有效克服大阻值反馈电阻引入的噪声,尤其适用于Si-PIN等半导体探测器。将该电荷灵敏前置放大器与BPX66型Si-PIN探测器连接,在室温下对241Am源进行测量,其能量分辨率可达到3.03%@59.5 keV。     

航空数γ能谱测量系统的研制

航空数字化γ能谱测量系统以NaI(T1)晶体(10 inm×10 minx40 mm)和光电倍增管构成的闪烁计数器为丫射线探测器,采用4条下测晶体和1条上测晶体组合成航空γ能谱测量系统的探头,设计了温度传感器、电流反馈型前置放大器和低纹波高压供电电路,实现了γ光子与核信号的转换;采用Y/U双通道数控增益放大器、双回路自...     

数字化PWM技术在电流传感器中的运用

提出了利用DSP实现PID控制,结合DSP芯片内部定时器模块产生PWM信号,最后由该信号通过反馈电路产生相应的补偿电流,根据被测电流与补偿电流的安匝比关系即可得到待测电流值。经过实验测试,该设计可用于交直流信号测量。研究证明,该技术使新型电流传感器具有高稳定性。     

瞬态微弱信号输出稳定性分析

本文分析了在辐射探测瞬态微弱信号获取中,系统输出不稳定的原因,并通过改变放大电路中的反馈网络结构,利用频域特性,采用最佳相位补偿的方法实现微弱信号稳定放大输出。最后利用CZT探测器在低能γ射线的辐射探测系统中验证测试,实验表明,辐射脉冲信号调理系统通过增加稳定性措施后,可有效提高CZT探测器对~(241)Am源的能量分辨率。     

一种抑制高增益直流耦合放大电路中直流漂移的电路

直流漂移现象在直流耦合放大电路中是不可避免的,放大器的放大倍数愈大,在输出端出现的直流漂移现象就愈严重.本文提出了一种可以有效抑制高增益低噪声直流耦合快前置放大电路中的直流漂移的电路.将此电路用于我们所设计的高增益(Av≥1000)直流放大器中,有效抑制了输出端的直流漂移.对该放大器进行了100h的工作测试,结果输出直流漂移小于±3mV.     

一种快前置放大电路的研制

简要介绍了研制的快前置放大电路,该电路是一个完全的直流放大器,具有较高的电压增益(Ar≥900),较快的上升沿(tr≤4ns),低噪声(等效输入噪声电压VN≤14μV),电路中引入贝塞尔滤波电路和反相求和电路,有效抑制了直流漂移,使电路具有极好的直流稳定性和增益稳定性,该电路主要适用于快探测器,如硅雪崩光电二极管探测器,也可用于加速器束流诊断系统,放大来自束流位置探针、相位探针的微弱信号.     

电荷积分放大电路对测量电离室时间响应速度的影响

测量放大器的时间响应速度直接影响电离室时间响应速度的测量研究。本文介绍了选用电荷积分放大器设计测量电路的原因,分析了用稳定辐射源照射电离室单元产生阶跃电流信号的机理,提出了通过测量电流信号变化的过程来研究放大器时间响应速度的方法。通过实验研究了放大器的时间响应速度与探测器单元极间电容、放大器输入端保护电阻以及反馈积分电容大小的关系,得出放大器的时间响应速度与电离室极间电容和保护电阻的时间常数有关,而与反馈积分电容大小无关。这为电离室和测量电路的设计提供了理论指导。     

The Need for Flexibility in Amplifier Design

Improvements in detector resolution and increases in the sophistication of nuclear experiments have placed an entirely new emphasis on linear amplifier design. Just a few years ago it was necessary to have specialized amplifiers to deal with each specific problem. The lack of flexibility now plaguing most existing linear pulse amplifying systems is often quite annoying to the user. Invariably, the user will find the amplifying system failing in part to provide either adequate stability, polarity reversibility, clipping mode selection, control of rise and fall times, adequate control of gain, or threshold cut and expansion. What usually ensues is that large amounts of time and effort are expended in modifying existing amplifiers in order to accomplish the particular job at hand, or the Job is done with an existing system where poor amplifier performance is accepted as a necessary evil. In the past several years many notable pulse amplifiers have been produced. Among these are the DD-2, the A-8, and the alpha amplifiers designed under the direction of Fairstein, Borkowski, and Blankenship at the Oak Ridge National Laboratory. Although these amplifiers show exceptional performance in their particular specialized application, all of these amplifiers lack the flexibility desired in a modern general-purpose laboratory amplifier. What is needed today is an amplifying system possessing the best basic features of these highly successful amplifiers with the addition of the features mentioned earlier to obtain greater flexibility and therefore greater utility. In early 1961, an amplifying system of this type was introduced at LRL.     

一种灵活快速的可编程多功能逻辑电路

本文介绍一种用于ＬＶＤ径迹触发系统的逻辑电路，它采用可编程的读写随机存储器作为核心器件，速度快，功能灵活，性能稳定可靠，已在意大利Ｇｒａｎ Ｓａｓｓｏ实验室连续运行近３年。     

快速电荷灵敏放大器

本文介绍一种快速电荷灵敏放大器,它在基本的共源极-共基极组态放大器中插入一个共集电极组态放大节,改善了系统特征方程的根轨迹,增大了回路增益,从而有效地提高了放大器的瞬态响应特性。在外接零电容时上冲小于10％情况下,上升时间小于4.5ns,等效噪声线宽FWHME(Si)约1keV     

基于DSP技术的高速反馈系统

本文介绍一个用于加速器束流轨道校正的实时反馈系统，该系统采用高速浮点ＤＳＰ和高性能ＶＭＥ实时工作站、具有的响应速度、高度的灵活性和长期稳定性。文中介绍了其基本原理和结构以及对该系统的测试原理及测试结果。     

A Linear Amplifier Suitable for High Counting Rates

A linear amplifier suitable for high counting rates is described. The amplifier uses double-delay-line shaping to minimize base line shifts and to enable timing signals to be obtained from the zero crossover. Miniature delay lines are used and the amplifier is designed to work with lines as short as 100 nanoseconds. It has a maximum gain of 500 and a rise time of 18 nanoseconds. To minimize delay line reflections, the lines are terminated at both ends. A novel circuit is used to obtain the delay line shaping. The amplifier has good overload characteristics and is constructed very compactly. It plugs into a frame designed to accomodate a series of compatible circuits of modular design. The front panel space required is 3.6 by 7 inches. Circuitry and performance are described.     

A New Temperature Compensating Method for Logarithmic Amplifier

A new method of temperature compensation for a dc logarithmic amplifier is presented. By this method temperature effect on both parallel shift and slope variance of log I vs. VBE curve can be compensated easily by using only one compensating resistor of copper wire wound type. (hereafter called parallel and slope compensations.) An absolute compensation condition can be determined for each type of logarithmic transistors, like silicon NPN, germanium PNP irrespective of current measuring range. The temperature dependence of the logarithmic amplifier is reduced to 0.01 decade for the temperature range from 0°C to 50°C and the current range from 10-11 to 10-3A.     

反应堆中子注量率相对分布测量装置中多通道放大甄别器研制

为了测量反应堆内中子注量率分布,保证反应堆内活化 55 Mn- 58 Ni合金探测片γ计数测量的可靠性,本文研制了中子注量率分布测量装置中9通道放大甄别器。多通道放大甄别器性能指标测试与应用测试结果表明：每个通道放大器增益1～21连续可调、甄别器阈值独立连续可调,具有最大计数率高、灵敏度高、稳定性好、系统抗串扰能力强等优点;放大器增益长期稳定性≤1%,甄别器最小输入脉冲宽度≥ 0.1 μs,甄别器最大计数率≤4×10 6 s -1,能用于实时长期稳定测量反应堆内中子注量率分布。