用负温度系数NTC电阻限流有何缺点

2025年03月15日 03:48
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网友(1):

(1)压敏电阻是一种具有非线性伏安特性的电阻器件,主要用于在电路承受过压时进行电压钳位,吸收多余的电流以保护敏感器件。压敏电阻的最大特点是当加在它上面的电压低于它的阀值&uot;UN&uot;时,流过它的电流极小,相当于一只关死的阀门,当电压超过UN时,它的阻值变小,这样就使得流过它的电流激增而对其他电路的影响变化不大从而减小过电压对后续敏感电路的影响。利用这一功能,可以抑制电路中经常出现的异常过电压,保护电路免受过电压的损害。
例如:家用的彩电的电源电路中就使用了氧化锌压敏电阻,这里使用的压敏电阻压敏电压为,当瞬态的浪涌电压最大值(非有效值)超过时,压敏电阻就是体现他的钳位特性,把过高的电压拉低,让后级电路工作在一个安全的范围内。
(2)热敏电阻器的典型特点是对温度敏感,不同的温度下表现出不同的电阻值。负温度系数热敏电阻器(NTC)在温度越高时电阻值越低。
作用:热敏电阻也可作为电子线路元件用于仪表线路温度补偿和温差电偶冷端温度补偿等。利用NTC热敏电阻的自热特性可实现自动增益控制,构成RC振荡器稳幅电路,延迟电路和保护电路。在自热温度远大于环境温度时阻值还与环境的散热条件有关,因此在流速计、流量计、气体仪、热导中常利用热敏电阻这一特性,制成专用的检测元件。
这真的很难一下子说明白最好上硬之城看看吧。

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