宽带直流放大器

针对小信号的幅度小、干扰大,线性放大难和提取难度大等问题,设计一种宽带直流放大器,是以单片机AT89C55WD和FPGA为控制核心,由可变增益放大器AD603为核心的放大电路、前级信号调理电路、后级功率放大电路和滤波电路组成。该放大器具有高增益且增益连续可调、输出波形无明显失真、有效抑制零点漂移和噪声、可输出大功率等特性．且在0-10MHz的频带内信号可放大0～75dB,带宽设置为5MHz或10MHz两种,输出信号峰峰值高达20V。     

宽带直流放大器

针对小信号的幅度小、干扰大,线性放大难和提取难度大等问题,设计一种宽带直流放大器.是以单片机AT89C55WD和FPGA为控制核心,由可变增益放大嚣AD603为核心的放大电路、前级信号调理电路、后级功率放大电路和滤波电路组成.该放大器具有高增益且增益连续可调、输出波形无明显失真、有效抑制零点漂移和噪声、可输出大功率等特性,且在0～10 MHz的频带内信号可放大0～75 dB,带宽设置为5 MHz或10 MHz两种,输出信号峰峰值高达20 V.     

工作点稳定的偏置电路

前面叙述单管放大器的原理时已经指出:晶体管在静态时必须建立位于放大区中部的静态工作点Q,以使晶体管具有电流放大作用,并使交流信号输入时不会产生输出信号的失真,在放大电路中建立静态工作点,即产生直流偏置电流I_(BQ)与H_(CQ)的电路叫偏置电路。一、静态工作点不稳定的原因及对放大性能的影响:上面讲的单管放大器电路工作点是不稳定的,当环境温度上升,     

晶体管六声道前置放大器

面对SACD和DVD-Audi o多声道高质量音源的发展,便有了多声道前置放大器的需求。众所周知,用于高保真音响系统的前置放大器有两个基本特征,一是半导体电路的电源电压相当高,二是输出晶体管可给出的电流足够大。本文介绍的前置放大器的电源电压高达60V,其晶体管可给出的电流为15mA。该前置放大器的输出信号电压为25Vpp,谐波失真小于1%,即在20Hz～20kHz范围内输出信号电压为1Vef f,谐波失真小于0.01%。一、原理图1为前置放大器原理图。六个声道中的每个声道均由一个包含三个晶体管的组件构成。场效应管T1(BF245C)的偏压由偏置电路R1和R…     

一种基于动态阈值NMOS管的1．2V模拟乘法器

基于CSMC0．6μm DPDM CMOS工艺进行设计,利用4个动态闽值NMOS和2个有源电阻实现了一种1．2V低功耗模拟乘法器电路,既节省了输入晶体管数目,又节省了偏置晶体管和偏置电路．1．2V模拟乘法器的输入信号VinA的频率为5MHz,信号峰峰值为1．0V,输入信号VinB的频率为100MHz,信号峰峰值为0．5V时,输出信号Vout的峰峰值为0．35V,一次谐波和三次谐波的差值为40dB．1．2V模拟乘法器输出信号的频带宽度为375MHz,平均电源电流约为30μA,即动态功耗约为36μw,适合于便携式电子产品和带宽要求不太高（400MHz以下）的场合．     

调幅发射机用的功率放大器

本文描述的晶体管放大器包括能改进其效率和线性的电路,其方法是通过与输入调幅信号的包络和输出调幅信号的衰减包络之差同步的方式来改变集电极电源电压。这个差信号用来控制近似无损耗的直流变压器,该直流变压器是给放大器提供可变的集电极电源电压。利用这种电路,在调制信号负周期期间,使集电极电压自动降低,以改善其效率。而且晶体管的增益以如此方式变化,使得因晶体管非线性引起输出的任何失真被抵消。将电路稍加改变,可成为高功率电平的调制器。     

浅谈放大器的谐波失真与改善对策

失真是指输出信号相对输入信号波形的畸变,是放大器重要参数之一。谐波失真是常见的失真,当信号的频率及电平较高时,常伴有“咝咝”声,而实际声源并无此成份,这是由于电路的非线性产生了声源基频外的谐波,其谐波又被电路削波所致。在谐波失真中,偶次谐波对于基频信号的不良影响要比奇次谐波小得多,偶次谐波的出现虽然会影响基频的     

石英晶体振荡器的集成化设计

在分析典型的分立式共射共基晶体振荡器原理的基础上,通过建立电路模型,设计一种集成化的石英晶体振荡器.采用电压源电路作为缓冲放大器的基极偏置,去掉容值较大的旁路电容,振荡电路与缓冲放大器电路共用偏置分压电阻,缩短电路起振时间,减小电路版图面积.基于特征尺寸为0.35μm的chrt.35dg_sige工艺库,利用Cadence中的spectre仿真工具对电路进行仿真.结果显示:当电源电压为2.7V时,振荡频率为12.8MHz,起振时间约为1.3ms,输出波形的峰峰值约为0.8V,单边带相位噪声1kHz处为-142dBc/Hz,10kHz处为-150dBc/Hz,整个电路的直流功耗小于2.7mW.     

数字功放原理

<正> 数字功放也称D类功放,与模拟功放的主要差别在于功放管的工作状态。传统模拟放大器有甲类、乙类和甲乙类、丙类等。一般的小信号放大都是甲类功放,即A类,放大器件需要偏置,放大输出的幅度不能超出偏置范围,所以,能量转换效率很低,理论效率最高才25％。乙类放大,也称B类放大不需要偏置,靠信号本身来导通放大管;理想效率高达78.5％。但因为这样的放大,小信号时失真严重,实际电路都要略加一点偏置,形成甲乙类功放,这么一来效率也就随之下降。虽然高频发射电路中还有一种丙类,即C类放大,效率可以更高,但电路复杂、音质更差,音频放大中一般都不采用。这几种模拟放大电路的共同特点是晶体管都工作在线性放大区域中,它按照输入音频信号的大小控制输出的大小,就像串在电源与输出间的一只可变电阻,控制输出,但同时自身也在消耗电能。     

温度传感器校准系统中红外信号检测电路设计

为了提高红外探测器检测红外微弱信号的精度,采用晶体管恒流偏置电路,使用低噪声高速运算放大器构成了前置放大电路。运用电路理论建立放大电路的噪声等效模型,采用叠加法计算1级放大输出端的噪声电压。通过中温黑体炉红外辐射实验,测试电路性能,取得了500℃~700℃时的电压波形,计算得出信噪比为7.25×103。结果表明,红外探测器前置放大电路达到高信噪比、响应速率快、抗干扰强的应用要求,可以对红外微弱信号检测放大。     

三极管非线性放大失真特性研究

本系统依据三极管的工作特性,借助了可调电阻和模拟开关的结合,设计了一种三极管非线性放大失真研究装置。利用了STM32单片机的编程与数据处理能力,完成了对电路的控制和数据分析。研究了三极管放大电路多种失真的现象,分析每种失真的原因和正常放大的条件,实现了控制、测量、分析的一体化,并将失真波形与其THD值直观地展示。该装置简便了三极管放大特性的研究,提供了一个高效的集成自动化平台。     

A New Low Distortion Analog Multiplier

A new method has been proposed to reduce the mobility degradation effect on square-law characteristic of the MOS transistor. This method has been applied to an analog multiplier to reduce the harmonic distortion. The analog multiplier designed operates with 5 V power supply. The linear operating range for each input is 3 V. In this operating range the circuit provides a total harmonic distortion of THD=0.6% from X input to the output and THD=0.5% from Y input to the output for operating as voltage controlled amplifier. Similarly, the 3 dB bandwidths are specified as 32 MHz and 34 MHz for X and Y inputs, respectively. The multiplier topology proposed allows external adjustment of the distortion, which can be considered as another important advantage of the circuit. The results show that the new method is effective for reducing distortion.     

High frequency current mode oscillator employing fTintegration technique

A low distortion high frequency oscillator is described, which is a development of the recently proposed f_T-integrator, in which an amplitude control circuit is embedded inside the integrator. Simulation results suggest that, for the oscillation range 1-2.6 GHz, the total harmonic distortion (THD) of the output current signal is well below 0.5% for the output current level at 50% modulation depth (peak-to-peak). The phase noise of the oscillator is simulated to be -72 dBc/Hz at 1 MHz offset for 1% THD output current     

Carrier Distortion in Hysteretic Self-Oscillating Class-D Audio Power Amplifiers: Analysis and Optimization

An important distortion mechanism in hysteretic self-oscillating (SO) class-D (switch mode) power amplifiers-carrier distortion-is analyzed and an optimization method is proposed. This mechanism is an issue in any power amplifier application where a high degree of proportionality between input and output is required, such as in audio power amplifiers or xDSL drivers. From an average-mode point of view, carrier distortion is shown to be caused by nonlinear variation of the hysteretic comparator input average voltage with the output average voltage. This easily causes total harmonic distortion figures in excess of 0.1-0.2%, inadequate for high-quality audio applications. Carrier distortion is shown to be minimized when the feedback system is designed to provide a triangular carrier (sliding) signal at the input of a hysteretic comparator. The proposed optimization method is experimentally proven in an audio power amplifier leading to THD figures that are comparable to the state of the art. Experimental hardware is a hysteretic SO bandpass current-mode-controlled single-ended audio power amplifier capable of 45 W into 8 Omega or 80 W into 4Omega from a plusmn34 V supply with less than 0.03% THD from 100 Hz to 6.7 kHz. Carrier distortion is shown to account for this limitation in THD performance.     

一种可调高线性度跨导器

本文提出了一种新的跨导器结构,它采用CMOS复合对管实现,可以通过调节栅极电压改变跨导器的跨导值,适合应用于高线性的连续时间滤波器.仿真结果表明,在供电电压为5伏,输入差分信号峰峰值为2.3伏的情况下,可以达到小于0.5%的总谐波失真.     

A 6-b 12-GSamples/s track-and-hold amplifier in InP DHBT technology

This paper presents a 6-b 12-GSample/s track-and-hold amplifier (THA) fabricated in an InP-InGaAs-InP double heterojunction bipolar transistor (DHBT) technology. The THA is intended for the front end of a high-speed analog-to-digital converter in a digital-based electronic polarization-mode dispersion compensation circuit for a 10-Gb/s optical receiver. With a high-speed switched emitter follower and clocked track-to-hold transition operation, it shows the signal bandwidth over 14 GHz and features a total harmonic distortion (THD) compatible with 6-b operation with input frequency of 6 GHz and a sampling frequency of 12 GHz. The THD increases better than -23 dB with a 12-GHz input signal of 1 V/sub pp/, corresponding to a 4-b resolution, under a differential clock of 12 GHz.     

防破音D类音频功放的设计与应用

随着多媒体便携设备的普及,音频功放已经成为音频部分的标准配置,D类功放以其高品质高效的特点得到了越来越广泛的应用。在便携产品中,音频功放由于输入音乐信号过大或者电源电压过低,会产生削顶失真。采用防破音技术,可以通过自动增益调节技术来提供一个完美的解决方案。文章介绍了常见的防破音技术,提出了一种改进的AGC(自动增益控制)技术在D类功放中的设计与应用。改进的AGC技术通过对PWM输出的采样来判断失真程度,依据失真程度用防破音电路产生的PWM波形来自动调节运放增益,实现最大功率的无失真输出。     

单片机在大功率功放电路中的应用

大功率功放存在2大问题:第一是输出信号失真,主要有:非线性失真和削波失真,这会影响音质,严重时还会烧坏扬声器。第二是保护问题。主要有:扬声器短路保护、输出信号直流保护。保护做得不好,很容易烧坏功放输出管和扬声器。单片机具有强大的测控功能,可以用来解决大功率功放的失真校正和电路保护的问题。实践证明,本系统有较好的效果。将讨论如何用单片机ATMEL 89C2051实现这一目标。     

A CMOS low-distortion fully differential power amplifier withdouble nested Miller compensation

A four-stage fully differential power amplifier using a double-nested Miller compensated structure is presented. The multiple-loop configuration used results in a lower harmonic distortion, at least in the audio band, compared to conventional three-stage amplifiers with nested Miller compensation. Design criteria and stability conditions for good stability of amplifiers using a multiple- (greater than two) loop topology are presented. The amplifier operates with a single power supply which has a minimum value of 3 V. With a 5-V supply, power dissipation is 10 mW and total harmonic distortion (THD) is -83 dB for a -V_p-p differential output signal at 10 kHz and a load of 50 Ω. With an 8 Ω load and for a 10-kHz, 4-V _p-p output signal, THD is -68 dB. The chip area is 0.625 mm ² in a 1.5-μm single-poly, double-metal, n-well CMOS technology