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用 Cds 光敏电阻探测光讯号的线路图如图一。R 为 Cds 光敏电阻的暗电阻,R_L 为负载电阻,E 是偏压。R.H.Harada 用此线路推导了跨在负载电阻上的讯号或光生电压ΔV 为:ΔV=Δi/q_L=Eq_LΔq/(q+q_L)(q+Δq+q_L)如果Δq 比 q 或 q_L 小很多,上式可以简化为ΔV=Eq_LΔq/(q+q_L)~2……(1)其中:q=1/R;q_L=1/R_L;Δq 为光电导。从公式(1)可以看到,在一定的光讯号下引起的讯号电压ΔV 依赖於 E,Δq,q_L.R_L 值的选取要考虑和光敏电阻匹配。为了提高讯号电压,一个途径是,用在 Cds 光敏电阻中掺入灵敏中心,形成电荷倍增效应来提高Δq,但这种方法对弱光探测不太合适,因为它可能带来严重的噪声.另一个途径从公式(1)看到,可以提高 Cds 光敏电阳的工作电压。ΔV 和 E 成正比。一般的
The circuit diagram of detecting optical signal with Cds photosensitive resistance is shown in Fig.1. R is the dark resistance of the Cds photoresistor, R_L is the load resistance, and E is the bias voltage. RHHarada uses this line to derive the signal or photo-generated voltage ΔV across the load resistance as: ΔV = Δi / q_L = Eq_LΔq / (q + q_L) (q + Δq + q_L) If Δq is much smaller than q or q_L, Can be simplified as ΔV = Eq_LΔq / (q + q_L) ~ 2 where q = 1 / R, q_L = 1 / R_L, and Δq is photoconductivity. It can be seen from the formula (1) that the signal voltage ΔV caused by a certain optical signal depends on E, Δq, q_L. The value of R_L should be chosen to match the photoresistor. In order to increase the signal voltage, one approach is to incorporate a sensitive center in the Cds photoresistor to create a charge multiplying effect to increase Δq, but this method is not suitable for low light detection because it can cause severe noise. One way to see from equation (1) is to increase the operating voltage of Cds. ΔV is proportional to E. General