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  1. R

    Transistors / hfe / Active region conflicts

    An infinite resistance source does not mean that the device cannot receive current. It means than the device will receive the same set amount of current no matter if the device changes its resistance, unless it changes its resistance to compare to the current source, like turning itself off. If...
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    Transistors / hfe / Active region conflicts

    Yes, you are describing base width modulation or the Early effect. It is what makes the Vc-Ic curve have a slant instead of being horizontal. You can read all about it here and elsewhere. https://en.wikipedia.org/wiki/Early_effect Ratch
  3. R

    Transistors / hfe / Active region conflicts

    The back voltage is caused by uncovered charges due to the diffusion process. If Vbe cancels some of this back voltage, the diffusion will increase and the depletion region will become narrower because a smaller depletion region corresponds to a lessor back voltage. I am referring to the...
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    Transistors / hfe / Active region conflicts

    By definition, a voltage source has no internal resistance. In practice, it can be modeled as a ideal voltage source in series with a small resistor. Not quite so. A short circuit differs in that it does not have a voltage source in series with it. Most voltage sources have an internal...
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    Transistors / hfe / Active region conflicts

    A transistor always functions "normally", unless you apply too much voltage or do not limit its current and burn it out. Even within a circuit, it functions as a transconductance amplifier, just as an op-amp functions as a dual high amplification voltage amplifier even when it is externally...
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    Transistors / hfe / Active region conflicts

    Neither of the above graphs are really graphs of the device alone. Whenever you drive a transistor with a current source, you are inserting an external resistor from the current source into the base circuit. This external resistor is not part of the device. What you now have is a current...
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    Transistors / hfe / Active region conflicts

    You have to understand that a BJT operating in the active region without any external base, emitter, or collector resistance is a transconductance amplifying device. That is, a change in Vbe voltage controls a change in Ic collector current. In other words, a BJT by itself is a voltage...
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    Transistors / hfe / Active region conflicts

    You want to know why the collector of a BJT in the active region acts like a current generator? That is an easy question to answer. The Vbe brings the charge carriers into the base region where they are swept away into the collector circuit by the collector voltage. A small percentage of the...
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    help for circuit analysis

    Yes, and superposition applied to both voltage sources along with the current divider theorem produces good results easily. Ratch
  10. R

    Question: DC analysis of a transistor amplifier?

    Yes, base current is an indicator and somewhat proportional to the collector current. No, that is not correct. IC1 is the sum of the current existing in R1 AND the base current of IC2. Yes, that is correct. Wrong. IC1 is the value stated above. Yes, the emitter-base diode of IC2...
  11. R

    Voltage divider protected by Zener diode

    I don't know what you are trying to do, but I assume you want your output to be a constant voltage. It seems to me that R2 is just another resistive load in parallel with the load. I don't think you want that, so throw away R2. Calculated the max current the diode can handle from its wattage...
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    help for circuit analysis

    You can solve it with loop, node, branch, or superposition methods. Your choice. Homework problems have their own section, and Circuit Help is not it. Ratch
  13. R

    Come & get yer watts!!!

    Well, let's take them one at a time. I don't think "hungry" is the correct word. Speakers have a impedance and wattage, so the voltage and current are locked into those figures. A motor will draw more current when it is loaded. The windings will melt if the amount of heat caused by the...
  14. R

    So, how many "watts" is a 9-volt battery?

    The amount of energy that can be obtained from any battery is determined by the rate it is de-energized. If de-energized slowly, then more energy can be extracted. There are battery manuals that give the specs of various batteries. Ratch
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    BJT Basics questions

    First time I heard that. When someone tells me that a multi-junction device is biased a certain way, I want to know what junction they are talking about. Ratch
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    BJT Basics questions

    There are many circuits that will latch like a SCR does, but that does not mean they will have the same electrical characteristics and specification that a real SCR does. Making a latching circuit from two transistors does not demonstrate how a SCR works. It is a different and alternative...
  17. R

    BJT Basics questions

    D1 and D4 are not biased to anything because D2 and D3 are nonconductive at this point. A voltage has to be applied to both ends of a diode for it to become biased. Once D2 and D3 become conductive, then D1 and D4 will be biased. 0.7 volts for a silicon diode or 0.4 volts for a germanium...
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    BJT Basics questions

    There are four junctions in the submitted circuit. Which two junctions are you referring? What transistor are you referring for Vb=Ve? The circuit is a junction model of a SCR. It will not really work as a SCR anymore than two diodes will work as a BJT. Therefore, it is spurious to suggest...
  19. R

    BJT Basics questions

    For a PN junction, if you put a more positive voltage on the P slab, or equivalently a more negative voltage on the N slab, then you are forward biasing the junction. For the schematic shown, both transistors have their BE junctions forward biased and their BC junctions reversed biased. If...
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    Come & get yer watts!!!

    The best voltage or current for doing what? Power transfer? Please specify. Ratch
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