How to Reduce Reference Noise
how to reduce reference noise by half
abstract: a low-noise, 2.5v reference is constructed by stacking four 2.5v reference ics in series. the resulting 10v output is divided back to 2.5v, and a low-noise unity-gain buffer added. this stacked-reference design reduces noise because the noise from each ic, being random and uncorrelated, partially cancels each other out.
the low-frequency 1/f noise (lf noise) generated by a voltage reference at frequencies below 10hz is very hard to reduce. one design approach reduces lf noise by implementing a lowpass rc filter, but that requires high-valued capacitors and resistors. high-value capacitors have lower value leakage resistance, which causes voltage error and long-term instability due to an uncontrolled voltage divider with the high-value series resistors. high-value series resistors cause error by undesired voltage drops due to leakage currents and by generating their own thermal noise.
stacking multiple references will reduce lf noise. by using multiple voltage sources, each composed of a dc source and a noise source, the dc voltages increase linearly and the noise sources (if not correlated) sum geometrically in an rms fashion. adding four references, for example, each consisting of a vref generator and a vnoise generator, produces the following outputs:
the original ratio of noise voltage to dc reference voltage is divided in half.
figure 1 shows how to stack multiple references to generate a single, less noisy reference voltage. the resistors are parts of a high-stability metal-film network, and the op amp is selected for low noise, very low input-offset voltage, and low offset tempco.
figure 1. four 2.5v references are stacked to produce 10v. the output is then divided back to 2.5v, which reduces the noise voltage by half.
two types of 2.5v voltage references can be used in the design. table 1 and table 2 show the noise voltages that result from use of either the max6037 or the max6143 reference. each table shows the 0.1hz-to-10hz noise voltage for the four references individually, and for them in combination. (the dispersion in the ratios of rms to peak-to-peak (p-p) values is due to some subjectivity in the method used to measure those p-p values.)
table 1. noise voltage measurements of the circuit in figure 1 using the max6037 2.5v voltage reference measurement points noise (µvrms) noise(µvp-p)
reduced noise output(op amp, output to v-) 1.0 10
across reference a(outa to gnda) 1.9 20
across reference b(outb to gndb) 1.6 19
across reference c(outc to gndc) 1.7 20
across reference d(outd to gndd) 2.7 30
table 2. noise voltage measurements of figure 1 circuit using max6143 2.5v voltage references measurement points noise (µvrms) noise(µvp-p)
reduced noise output(op amp, output to v-) 0.27 2.2
across reference a(outa to gnda) 0.52 4.7
across reference b(outb to gndb) 0.60 4.8
across reference c(outc to gndc) 0.50 4.3
across reference d(outd to gndd) 0.55 4.7
as an additional benefit of this reference-stack arrangement, the portion of long-term drift due to noise will also be reduced.
a similar version of this article appeared as a design idea in the february 3, 2005 issue of edn magazine.
厦门火炬高新区17个项目开工 总投资额达43.4亿元
设计一种可持续数十年的电池供电型楼宇自动化系统
我国RV减速机国产替代之路任重道远
鲁大师2019硬盘性能排行公布 三星PM981成功夺冠
黑客针对医疗机构的攻击日益增加
How to Reduce Reference Noise
典型的E1接口连接器和实现
利元亨在激光焊接动力电池工艺上研发导入环形激光焊接技术
选择PCB组装中的自动X射线检测技术的原因是什么
在今年的5G形势下，华为有很大可能赶超苹果
【视频干货】利用汽车图像传感器向更安全的道路迈进
开关面板十大品牌排名_西蒙电气在行业排第几
谷歌被罚186亿后怒发飙：聘最强律师团反击欧盟
聆耳LinnerNC90头戴蓝牙耳机体验 降噪效果好音质不错
稳压电路当中怎么选择电阻？
升级aigo国民好物固态硬盘S500，给老电脑第二次生命
台湾加拿大合作推动燃料电池产业的发展
浅谈压控晶振的原理和特点
江西氢气发生器OEM 湖南氢氧发生器贴牌
三星将在其计算机上预先安装微软的Your Phone应用
abstract: a low-noise, 2.5v reference is constructed by stacking four 2.5v reference ics in series. the resulting 10v output is divided back to 2.5v, and a low-noise unity-gain buffer added. this stacked-reference design reduces noise because the noise from each ic, being random and uncorrelated, partially cancels each other out.
the low-frequency 1/f noise (lf noise) generated by a voltage reference at frequencies below 10hz is very hard to reduce. one design approach reduces lf noise by implementing a lowpass rc filter, but that requires high-valued capacitors and resistors. high-value capacitors have lower value leakage resistance, which causes voltage error and long-term instability due to an uncontrolled voltage divider with the high-value series resistors. high-value series resistors cause error by undesired voltage drops due to leakage currents and by generating their own thermal noise.
stacking multiple references will reduce lf noise. by using multiple voltage sources, each composed of a dc source and a noise source, the dc voltages increase linearly and the noise sources (if not correlated) sum geometrically in an rms fashion. adding four references, for example, each consisting of a vref generator and a vnoise generator, produces the following outputs:
the original ratio of noise voltage to dc reference voltage is divided in half.
figure 1 shows how to stack multiple references to generate a single, less noisy reference voltage. the resistors are parts of a high-stability metal-film network, and the op amp is selected for low noise, very low input-offset voltage, and low offset tempco.
figure 1. four 2.5v references are stacked to produce 10v. the output is then divided back to 2.5v, which reduces the noise voltage by half.
two types of 2.5v voltage references can be used in the design. table 1 and table 2 show the noise voltages that result from use of either the max6037 or the max6143 reference. each table shows the 0.1hz-to-10hz noise voltage for the four references individually, and for them in combination. (the dispersion in the ratios of rms to peak-to-peak (p-p) values is due to some subjectivity in the method used to measure those p-p values.)
table 1. noise voltage measurements of the circuit in figure 1 using the max6037 2.5v voltage reference measurement points noise (µvrms) noise(µvp-p)
reduced noise output(op amp, output to v-) 1.0 10
across reference a(outa to gnda) 1.9 20
across reference b(outb to gndb) 1.6 19
across reference c(outc to gndc) 1.7 20
across reference d(outd to gndd) 2.7 30
table 2. noise voltage measurements of figure 1 circuit using max6143 2.5v voltage references measurement points noise (µvrms) noise(µvp-p)
reduced noise output(op amp, output to v-) 0.27 2.2
across reference a(outa to gnda) 0.52 4.7
across reference b(outb to gndb) 0.60 4.8
across reference c(outc to gndc) 0.50 4.3
across reference d(outd to gndd) 0.55 4.7
as an additional benefit of this reference-stack arrangement, the portion of long-term drift due to noise will also be reduced.
a similar version of this article appeared as a design idea in the february 3, 2005 issue of edn magazine.
厦门火炬高新区17个项目开工 总投资额达43.4亿元
设计一种可持续数十年的电池供电型楼宇自动化系统
我国RV减速机国产替代之路任重道远
鲁大师2019硬盘性能排行公布 三星PM981成功夺冠
黑客针对医疗机构的攻击日益增加
How to Reduce Reference Noise
典型的E1接口连接器和实现
利元亨在激光焊接动力电池工艺上研发导入环形激光焊接技术
选择PCB组装中的自动X射线检测技术的原因是什么
在今年的5G形势下，华为有很大可能赶超苹果
【视频干货】利用汽车图像传感器向更安全的道路迈进
开关面板十大品牌排名_西蒙电气在行业排第几
谷歌被罚186亿后怒发飙：聘最强律师团反击欧盟
聆耳LinnerNC90头戴蓝牙耳机体验 降噪效果好音质不错
稳压电路当中怎么选择电阻？
升级aigo国民好物固态硬盘S500，给老电脑第二次生命
台湾加拿大合作推动燃料电池产业的发展
浅谈压控晶振的原理和特点
江西氢气发生器OEM 湖南氢氧发生器贴牌
三星将在其计算机上预先安装微软的Your Phone应用