照片二极管

光电二极管是双终端半导体P-N结设备并设计用于反向偏置。图中给出了该装置的基本偏置布置，构造和符号。它要么安装在半透明案例中或其半导体连接在光学镜片下方的连接。如图所示，输出电压从串联连接的负载电阻R跨越串联连接的负载电阻R.这种电阻可以连接在二极管和地面或电源的二极管和正端子之间。

pn结反向偏置时,反向saturation current flows due to thermally generated holes and electrons being swept across the junction as the minority carriers. With the increase in temperature of the junction more and more hole-electron pairs are created and so the reverse saturation current I_0.增加。通过照亮连接点可以具有相同的效果。当光能轰击P-N结时，它脱落了价电子。撞击结的较大光电越大，二极管中的反向电流越大。它是由于产生越来越多的电荷载流子，随着照明水平的增加。这清楚地显示在'不同强度水平的数字。这黑暗的电流是当没有光线发生时存在的电流。这里应注意，电流仅用正施加的偏差等于v_问：. The almost equal spacing between the curves for the same increment in luminous flux reveals that the reverse saturation current I_0.用光通量线性增加，如图所示。反向电压的增加不会显着增加反向电流，因为所有可用的电荷载流子已经被扫描在整个交界处。用于减少反向饱和电流i_0.to zero, it is necessary to forward bias the junction by an amount equal to barrier potential. Thus the photodiode can be used as a光电导装置。

在去除光电二极管上施加的反向偏压时，在二极管照明的同时，少数竞争载流子继续扫过整个交界处。这具有增加P侧的孔的浓度和N侧的电子的浓度，但是阻挡电位在P侧和N侧的阳性上是负的，并且通过流出的孔产生在结合结合时，P到N-侧和来自N到P侧的电子。因此，少数竞争因子的流动倾向于降低阻挡势。

When an external circuit is connected across the diode terminals, the minority carrier; return to the original side via the external circuit. The electrons which crossed the junction from P to N-side now flow out through the N-terminal and into the P-terminal This means that the device is behaving as a voltage cell with the N-side being the negative terminal and the P-side the positive terminal. Thus, the photodiode is & photovoltaic device as well as photoconductive device.

光电二极管具有比硫化镉的光敏敏感性远得远。LDRS，但在光线水平上提供公平的响应。通常，LDR是用于慢动作直接耦合光电电平传感应用的理想选择，而光电二极管是用于快速作用AC耦合信令应用的理想选择。典型的光电二极管应用包括检测（可见和不可见），解调，切换，逻辑电路需要稳定性和高速，字符识别，光通信设备，红外遥控器电路编码器等