Vbe saturation voltage11/14/2023 ![]() ![]() Also, the large the base, the lower the base resistance, so less voltage drop across the base resistance. Since IC 0 the voltage drop across Rc is zero and so VoVcc. ![]() so the higher the hfe, the lower the Vbe. If the voltage is less than the voltage required to forward bias the base-emitter junction then the current vi IB 0 and thus the transistor is in the cutoff region and IC 0. Calculations can be made to find the temperature coefficient of the diode. A BJTs data sheet will have a graph of base-emitter saturation voltage VBE(SAT) across collector current (IC) and temperature. The higher the hfe, the smaller the current at a given Ie. sheet will have a typical graph of forward voltage across forward current and temperature. Is VBE 0.7 in saturation Saturation mode : VBE 0.7V, VCE 0.2V. As V1 is increased from 0.35, at some point, the net current flow will stop and reverse and be from emitter to collector. Transistors are having saturation voltage range from 0.7V and below but for a circuit designed for hard saturation, the VCE will be lower. So if V2 is 0.55V, and V1 is 0.35V, then Vce 0.2V, and the device may very well be in saturation, with a net current flowing from collector to emitter. KSC is high voltage and low current, maybe if I look for a low voltage device in TO-126, I might have better luck both in hfe and Vbe. If the reading is below 0.3V, the transistor is at saturation. I am thinking about looking for low voltage transistors that has high current capability. Any current through the base resistance with create a voltage that adds to the Vbe. The Vbe is related to the current capability of the transistor. So by definition, larger the transistor, the lower the Vbe.Īs for hfe, think of it this way, there is always a parasitic base resistance in series from the pin to the base inside. 100 transistor will reduce by 120mV.and so on. If you have 10 transistors in parallel, using the same equation will give you a reduction of 60mV. If you calculate for two transistor where each contribute half, the equation gives 18mV reduction in Vbe. If you think of it that way, for two transistors, each will contribute only half the current.įrom equation \delta V be= V T ln(I 1/I 2). It's like many transistors in parallel together. ![]() Stack Exchange Network Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. If you look under the microscope, the power transistors have emitter like fingers extending out to cover more area. Applying KVl Ic (VTH - VBE)/((1/B)RTH+(B+. For a given Ie, Vbe is lower for larger transistor for very simple reason, The large transistor is like a bunch of small transistors in parallel. ![]()
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |