为解决低频小信号在大功率放大时带载能力不强,输出波形易振荡与交越失真,易烧负载等问题,设计了由前置小信号放大、功率驱动放大、负载保护、电源等电路构成的低频小信号放大器系统。该系统的前置放大由阻抗匹配和两级低噪放大组成,功...为解决低频小信号在大功率放大时带载能力不强,输出波形易振荡与交越失真,易烧负载等问题,设计了由前置小信号放大、功率驱动放大、负载保护、电源等电路构成的低频小信号放大器系统。该系统的前置放大由阻抗匹配和两级低噪放大组成,功率放大采用带保护功能的音频IC芯片LM3886,负载保护采用带过流和直流偏移检测的C1237HA芯片。测试结果表明,该系统实现了30 Hz~20 k Hz范围内小信号的20 W以上的功率放大,具有失真率低,输出功率大、效率高、输出信号音质好的优点,可用于大功率音响的设计中。展开更多
Hydroxyproline is the main component of collagen,accounting for 20% or so of collagen,and metabolic changes in bone collagen directly affect the level of hydroxyproline in the blood.So inspecting the content of hydrox...Hydroxyproline is the main component of collagen,accounting for 20% or so of collagen,and metabolic changes in bone collagen directly affect the level of hydroxyproline in the blood.So inspecting the content of hydroxyproline is very important for pathogenesis and prophylactico-therapeutic measures on osteodystrophy of dairy cows.This experiment monitored and studied the change regularity of serum calcium,serum phosphorus and serum free hydroxyproline of perinatal cow in Hebei Province,and discussed a new and early diagnosis way for osteodystrophy.Thus,effective control measures could be implemented before the bone became deformed without any clinical symptom.The paper provided a theoretical foundation for early diagnosis of perinatal cow.展开更多
文摘为解决低频小信号在大功率放大时带载能力不强,输出波形易振荡与交越失真,易烧负载等问题,设计了由前置小信号放大、功率驱动放大、负载保护、电源等电路构成的低频小信号放大器系统。该系统的前置放大由阻抗匹配和两级低噪放大组成,功率放大采用带保护功能的音频IC芯片LM3886,负载保护采用带过流和直流偏移检测的C1237HA芯片。测试结果表明,该系统实现了30 Hz~20 k Hz范围内小信号的20 W以上的功率放大,具有失真率低,输出功率大、效率高、输出信号音质好的优点,可用于大功率音响的设计中。
基金Supported by Natural Science Foundation of Hebei Province(2009)Modern Agricultural Research Program of Hebei Department of Science and Technology(2013)
文摘Hydroxyproline is the main component of collagen,accounting for 20% or so of collagen,and metabolic changes in bone collagen directly affect the level of hydroxyproline in the blood.So inspecting the content of hydroxyproline is very important for pathogenesis and prophylactico-therapeutic measures on osteodystrophy of dairy cows.This experiment monitored and studied the change regularity of serum calcium,serum phosphorus and serum free hydroxyproline of perinatal cow in Hebei Province,and discussed a new and early diagnosis way for osteodystrophy.Thus,effective control measures could be implemented before the bone became deformed without any clinical symptom.The paper provided a theoretical foundation for early diagnosis of perinatal cow.