If we compare the above result with the result that we acquired at the end of this post, we find that the result I CQ = 2.35mA is by far lower than the above 5.45mA which suggests that normally BJTs are never operated in the saturation level in circuits, rather at much lower values. When a enough voltage (VIN > 0.7 V) is implemented. Solving a practical example to find the saturation current of a BJT: Based at the voltage implemented at the bottom terminal of a transistor switching operation is performed. ![]() The saturation current developing in the above condition could be interpreted wit the following expression: In circuits with fixed-bias configuration, as indicated in Fig 4.10 a short circuit could be applied, which may result in a voltage across RC equal to the voltage Vcc. Put simply, assign VCE = 0V and then you can calculate VCEsat easily. ![]() This implies that whenever it is required to quickly evaluate the approximate saturation collector current for a given BJT in a circuit, you may simply assume an equivalent short circuit value across the collector emitter of the device and then apply it in the formula for getting the approximate collector saturation current. Also, the collector current is comparably high on the characteristic curves.Ī practical design implementation for the above formula can be seen in the fig 4.9 below: Observe that it is that specific region where the joint of the characteristic curves with the collector-to-emitter voltage is lower than VCEsat or at the same level. We can see an operating point within the saturation region in the figure 4.8a. In transistors configurations it is normally ensured that the device does not reach its saturation point, since in this situation the base collector ceases to be in the reverse biased mode, causing distortions in the output signals. ![]() Having said this, the maximum saturation level will be always as per the maximum collector current of the device as outlined in the datasheet of the device. We can take the example of a fully wet sponge, which may be in its saturated state when there's no space in it to hold any further liquid.Īdjusting the configuration may result in quickly changing the saturation level of the transistor. The term saturation refers to any system where the specification levels have attained the maximum value.Ī transistor may be said to be operating within its saturating area, when the current parameter reaches the maximum specified value.
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