Most engineers know that they can use an inexpensive, three-terminal adjustable regulator, such as Fairchild Semiconductor’s LM317, as an adjustable regulator to only some necessary value of voltage, such as 36 or 3V. This value cannot be less than 1.25V without employing other approaches, however. The devices’ inner reference voltage is 1.25V, and their output voltage accordingly cannot be less than this value without potential bias (Reference 1). One way to solve this problem is to use a reference-voltage source based on two diodes (Reference 2). Although this approach is suitable for a 1.2 to 15V or higher-voltage regulator, it is not appropriate for an extra-low-voltage fixed- or adjustable-voltage regulator. The two 1N4001 diodes it employs do not provide the needed potential bias of 1.2V, and they have additional temperature instability of approximately 2.5 mV/K (Reference 3). Hence, additional temperature drifting of the output voltage is approximately 100 mV; it is more than 6% for a 1.5V output voltage and 10% for a 1V output voltage if you adjust the temperature to 20°C—a typical indoor situation. You can solve these problems by using a Fairchild Semiconductor LM185 or an Analog Devices AD589 adjustable-voltage-reference IC. These devices are expensive, however, and, in this case, they require not only additional zero adjustment but also matching. These adjustments at their reference voltages are 1.215 to 1.255V and 1.2 to 1.25V for the LM185 and AD589, respectively. Note that the reference voltage of the LM317 is 1.2 to 1.3V.

Figure 1 This circuit is an inexpensive approach using a simple 0 to 3V adjustable regulator.

Figure 1 shows an inexpensive approach using a simple 0 to 3V adjustable regulator. You implement the necessary potential bias using a simple temperature-stabilized constant-current source (Reference 4). You calculate this current source using the following equation: I=(VF–VEBO)/(R5+R6), where VF is D1’s forward voltage of approximately 2V and VEBO is Q1’s emitter-base voltage of approximately 0.68V. The current is approximately 1.32/(R5+R6). The constant-current source creates a bias voltage of approximately –1.25V on resistor R3. You implement the zero adjustment using resistor R6, which can change the current of the constant-current source. Resistor R5 protects transistor Q1. You can use D1 as a light indicator. You can adjust the output voltage using resistor R2. Calculate the output voltage as follows: VOUT=VREF(1+R2/R1)–VR3, where VREF is the reference voltage of IC1 and VR3 is some compensative voltage of resistor R3. You should establish this voltage to equal the reference voltage for its compensation. In this case, VOUT=VREF(R2/R1). With R2 having a value of 1.2 kΩ,this circuit found use as the equivalent of a typical battery with an output voltage of 1.56V for development projects.

Use an LM317 as 0 to 3V adjustable regulator的更多相关文章

  1. STM32-正弦波可调(50HZ~20KHZ可调、峰峰值0~3.3V可调)

    1.原理: 通过定时器每隔一段时间触发一次DAC转换,然后通过DMA发送正玄波码表值给DAC. 当需要改变频率HZ时,只需要修改定时器频率即可(最高只能达到20KHz) 当需要改变正玄波的正峰峰值/负 ...

  2. 一个5.0/3.3V双向通讯的电路

    来自群友 西江月-梧州 的分享 硬件程工-深圳福永(79993868) 17:06:33 当3.3V高时二极管阳极为3.3V,阴极接了10K上拉为5V,二极管的压降为反向,此时二极管不导通. 硬件程工 ...

  3. 1V升3V芯片,1V升3.3V芯片,大电流的,低功耗

    一般来说,1V的电压实在很低了,即使是干电池的话,再1V时,也是基本属于没电状态了.还有一种是干电池输出电流大时,也会把干电池的电压从1.5V拉低到1V左右. 更多的是客户对于1V时要能升到3V或者3 ...

  4. Current-sense monitor and MOSFET boost output current

    A previous Design Idea describes a programmable current source that used a three-terminal National S ...

  5. 常见电子元器件检测方法。——Arvin

    电子设备中使用着大量各种类型的电子元器件,设备发生故障大多是由于电子元器件失效或损坏引起的.因此怎么正确检测电子元器件就显得尤其重要,这也是电子维修人员必须掌握的技能.我在电器维修中积累了部分常见电子 ...

  6. Linux学习 : 裸板调试 之 配置UART

    1.UART原理说明 发送数据时,CPU将并行数据写入UART,UART按照一定的格式在一根电线上串行发出:接收数据时,UART检测另一根电线上的信号,串行收集然后放在缓冲区中,CPU即可读取UART ...

  7. STM32 DAC的配置与使用

    本博文转自:http://blog.chinaunix.net/uid-24219701-id-4101802.html STM32 的 DAC 模块(数字/模拟转换模块)是 12 位数字输入,电压输 ...

  8. 基于DDS的任意波形发生器

    实验原理 DDS的原理 DDS(Direct Digital Frequency Synthesizer)直接数字频率合成器,也可叫DDFS. DDS是从相位的概念直接合成所需波形的一种频率合成技术. ...

  9. jquery点击label触发2次的问题

    今天写问卷的时候遇到个label点击的时候,监听的click事件被执行两次:产生这个的原因么...事件冒泡 <div class="questionBox checkBox" ...

随机推荐

  1. Machine Learning系列--EM算法理解与推导

    EM算法,全称Expectation Maximization Algorithm,译作最大期望化算法或期望最大算法,是机器学习十大算法之一,吴军博士在<数学之美>书中称其为“上帝视角”算 ...

  2. Machine Learning系列--判别式模型与生成式模型

    监督学习的任务就是学习一个模型,应用这一模型,对给定的输入预测相应的输出.这个模型的一般形式为决策函数:$$ Y=f(X) $$或者条件概率分布:$$ P(Y|X) $$监督学习方法又可以分为生成方法 ...

  3. 利用json模块解析dict报错找不到attribute 'dumps'[python2.7]

    [背景] 环境: RHEL 7.3 版本: python2.7 [错误情况] 写了一个简单的python脚本 将dict转换为json 脚本如下: #!/usr/bin/python #-*- cod ...

  4. json数据操作

    <!DOCTYPE HTML> <html> <head> <meta charset="utf-8"> <title> ...

  5. C++如何取得int型的最大最小值

    转:http://www.cnblogs.com/alex4814/archive/2011/09/12/2174173.html 當題目涉及到求最大最小值時,最初的比較數字就應當設置爲INT_MAX ...

  6. break、continue多层循环处理

    使用break xxx跳出多层循环的代码如下: for(String s: arr){ labelA: for(String ss: arr) { for(String sss: arr) { Sys ...

  7. (转)粒子编辑器Particle designer属性的介绍

    转载:http://blog.csdn.net/ym19860303/article/details/9210539 Particle designer粒子编辑器可到这里下载(包含授权码):http: ...

  8. js屏蔽手机的物理返回键

    $(document).ready(function() { if (window.history && window.history.pushState) { $(window).o ...

  9. CentOS7.5 firefox Flash插件更新

    CentOS7自带的firefox没有flash插件,所以是没有办法在网页上看视频的,需要自己手动安装 1.下载 打开flash官网https://get.adobe.com/flashplayer/ ...

  10. Es6懒加载

    const Login = resolve => require(['@/components/Login'], resolve) 注(当路由被访问的时候才加载这个组件)