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在红外系统中,目标的辐射经过红外探测器之后通常只能得到微伏级电讯号。为了满足终端设备要求,必须用高增益的放大器对信号加以放大。随着放大器增益的提高,系统的噪声也增大。而放大系统内部噪声与其工作状态密切相关。若单纯追求放大器的增益而忽略降低放大系统的噪声将使输出级的动态范围被噪声填满。为了提高设备的灵敏度必须降低噪声。因此,低噪声前置放大器的设计和调试是提高系统灵敏度的重要环节,而低噪声前置放大器的理论是设计的基础。
In the infrared system, the target’s radiation typically passes through the infrared detector to get only micro-volt electrical signals. In order to meet the requirements of the terminal equipment, the signal must be amplified with a high-gain amplifier. As amplifier gain increases, system noise also increases. The internal noise amplification system and its working conditions are closely related. Simply pursuing the gain of the amplifier and neglecting to reduce the noise in the amplification system will make the dynamic range of the output stage filled with noise. In order to improve the sensitivity of the equipment, the noise must be reduced. Therefore, the design and debugging of low-noise preamplifier is an important part of improving system sensitivity, and the theory of low-noise preamplifier is the basis of design.