Negative-Resistance Load Cance
negative-resistance load canceller allows voltage reference to drive heavy loads
abstract: this application note discusses how to build a high output drive voltage reference without sacrificing temperature drift, initial accuracy, and noise that cannot internally drive enough current.
the task of driving a load with a reference requires some attention. after determining the supply voltage and output voltage, the parameters to consider include the output-voltage temperature coefficient, initial accuracy, drift, noise, line and load regulation, package size and type, power consumption, stability with various capacitive loads, and the required source and sink capability.
a common problem is the need to source or sink more current than the reference can provide. a precision unity-gain buffer amplifier offers an adequate solution in applications that can tolerate its additional drift, noise, and gain inaccuracy. a serious drawback, however, is the buffer's potential instability when driving capacitive loads, such as the well-bypassed reference inputs of an a/d or d/a converter. attempting to guarantee the buffer's stability by introducing an isolation resistor, between op-amp output and capacitive load, further degrades the reference circuit's accuracy.
another alternative is to cancel the load, that is, to make it appear like a large resistance. if load resistance is made to appear large, the remaining load is composed of any capacitance that may be in parallel with the load resistance. the load may be cancelled by placing a negative resistance in parallel with the load's positive resistance. if the magnitudes of these positive and negative resistances can be made equal, the effective load resistance becomes infinite. unlike a buffer amplifier, the negative-resistance circuit in figure 1 adds negligible output error.
figure 1. this circuit presents a negative resistance between vin and ground.
the input resistance from vin to ground is negative, and calculated as follows:
adding the circuit in figure 1 to the output of an ultra-stable reference capable of driving ±15ma (figure 2) enables the reference to drive ±50ma or more. with perfectly matched components, the reference would source negligible dc current. with 1% resistors in the negative-resistance circuit, the required worst-case output current is ±2ma. load cancellation improves output accuracy by lowering the error due to reference output resistance. it also minimizes any drift due to self-heating, especially when the output current is large and the difference between the output voltage and reference-supply voltage is also large. in addition,the circuit is unconditionally stable with any capacitive load.
figure 2. placing the figure 1 circuit in parallel with the load of a voltage reference (47ω in this case) cancels most of the reference's resistive load.
a similar version of this article appeared in the march 19, 2001 issue of electronic design magazine.
全国规模最大的C-V2X智慧高速公路即将在重庆投用使用
微软推送更新以优化触控键盘
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Negative-Resistance Load Cance
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abstract: this application note discusses how to build a high output drive voltage reference without sacrificing temperature drift, initial accuracy, and noise that cannot internally drive enough current.
the task of driving a load with a reference requires some attention. after determining the supply voltage and output voltage, the parameters to consider include the output-voltage temperature coefficient, initial accuracy, drift, noise, line and load regulation, package size and type, power consumption, stability with various capacitive loads, and the required source and sink capability.
a common problem is the need to source or sink more current than the reference can provide. a precision unity-gain buffer amplifier offers an adequate solution in applications that can tolerate its additional drift, noise, and gain inaccuracy. a serious drawback, however, is the buffer's potential instability when driving capacitive loads, such as the well-bypassed reference inputs of an a/d or d/a converter. attempting to guarantee the buffer's stability by introducing an isolation resistor, between op-amp output and capacitive load, further degrades the reference circuit's accuracy.
another alternative is to cancel the load, that is, to make it appear like a large resistance. if load resistance is made to appear large, the remaining load is composed of any capacitance that may be in parallel with the load resistance. the load may be cancelled by placing a negative resistance in parallel with the load's positive resistance. if the magnitudes of these positive and negative resistances can be made equal, the effective load resistance becomes infinite. unlike a buffer amplifier, the negative-resistance circuit in figure 1 adds negligible output error.
figure 1. this circuit presents a negative resistance between vin and ground.
the input resistance from vin to ground is negative, and calculated as follows:
adding the circuit in figure 1 to the output of an ultra-stable reference capable of driving ±15ma (figure 2) enables the reference to drive ±50ma or more. with perfectly matched components, the reference would source negligible dc current. with 1% resistors in the negative-resistance circuit, the required worst-case output current is ±2ma. load cancellation improves output accuracy by lowering the error due to reference output resistance. it also minimizes any drift due to self-heating, especially when the output current is large and the difference between the output voltage and reference-supply voltage is also large. in addition,the circuit is unconditionally stable with any capacitive load.
figure 2. placing the figure 1 circuit in parallel with the load of a voltage reference (47ω in this case) cancels most of the reference's resistive load.
a similar version of this article appeared in the march 19, 2001 issue of electronic design magazine.
全国规模最大的C-V2X智慧高速公路即将在重庆投用使用
微软推送更新以优化触控键盘
自制创意激光竖琴
李建林：5G技术借助虚拟现实等技术，加快智慧医疗建设步伐
燃料电池汽车--未来“氢经济”的动力
Negative-Resistance Load Cance
来看一下频谱仪的射频前端设计吧
!SML02/SML02/SML02信号发生器 小兵/李S
台积电7纳米量产倒计时,准确时间定在2018年第二季度
工业机器人三类编程方法详解
AI加速智能家居分布式语音技术发展
2021年全球汽车出货量可望达8350万辆
腾讯研究院院长司晓正式发布了《腾讯人工智能白皮书：泛在智能》
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时间继电器自动控制星三角降压启动控制电路
关于半导体良率的详细介绍和分析
掌上电脑(PDA)
人工智能创业公司应尽快将技术应用方案落地 尽早商业化
电气设备触头按构造和特性可分为哪几种
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