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    Differential amplifier

    In case the school did not provide a comparator in the bag of components to use, the LM358 makes a fair comparator in a circuit such as this. You might consider generating the reference voltage directly from the sensor itself by using a very long time constant RC filter, if sensor drift is a...
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    Drill bits for homemade PCBs?

    I still have mine, purchased in the late 1970s ~$400. Precision machined cast iron & steel. Made in Japan. Height=16" shown next to a Dremel Tool for comparison. I added the clamp bar to the base. This stays on the shelf except for special drilling jobs. As far a I can tell nobody still makes these.
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    Test Rig

    Have you considered using six variable resistors in a string driven by a constant current source? If each cell doesn't need to be discharged to zero volts, then each test cell resistance could be a variable resistance in series with a fixed resistance.
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    Homemade DC generator(dynamo) with a spinning coil

    LED bulb?
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    Homemade DC generator(dynamo) with a spinning coil

    If you spin the magnet, does that produce AC or DC current in the coil? What is an alternator? If you have a stationary field and spin a coil/commutator, does that produce AC or DC? Does it depend on the design of the commutator? For a commutator you could put insulating tape on the shaft...
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    Resistance of different points of a circuit

    There is some conceptual difficulty with the terminology "resistance at a point" because resistance is measured between two points. From your calculations it is not immediately clear what that other point is.
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    Transistor bias configuration

    Considering the severity of gun control in the U.K., I'm surprised that such a statement would even be allowed.
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    Transistor bias configuration

    If you are thinking in terms of right & wrong, then you have probably missed the essence of that discussion. The issue is whether it is most appropriate to explain transistor circuit operation using concepts from semiconductor physics, or using principles from engineering circuit design. While...
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    Transistor bias configuration

    Indeed that is true; which is why BJT bias networks are designed to forward bias the base-emitter junction with a current in order to have the junction develop the corresponding voltage. As you said, the transistor doesn't care. Circuit designers do not care much what particular value Vbe...
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    Transistor bias configuration

    There are no professional gladiators in this Colosseum, except, possibly for the moderators. Entertainment here is provided by spectators willing to jump down on the blood & sand to make the good kill. Also, the zombies will rise again! How many times do you need to kill the same zombie before...
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    Transistors / hfe / Active region conflicts

    I think it is quite obvious that you have no idea what a load line is or how it works.
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    Transistors / hfe / Active region conflicts

    Why do you frequent an electronics forum and expect explanation of internal device physics? The terminal characteristics of devices are what make circuits work. Perhaps if one were to hang out in a physics forum instead, then topics of internal junction physics would be more relevant. And as...
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    Transistors / hfe / Active region conflicts

    Perhaps you should consult a tutorial on class-B amplifiers where the output is a direct function of the base current. http://www.electronics-tutorials.ws/amplifier/amp_6.html
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    Transistors / hfe / Active region conflicts

    One must surely realize that adding a current source does not make much of a circuit given the infinite source resistance providing isolation. However, a voltage source has zero source resistance - there is no isolation at all. A voltage source is not part of the device. It is external to the...
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    Transistors / hfe / Active region conflicts

    So here you are at the beginning, again. Since you have some conceptual difficulty accepting that a current source controls the sourced current, there is no point to this discussion.
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    Transistors / hfe / Active region conflicts

    Where is the contradiction? One statement described operation of a transistor in isolation. The other statement addressed the operation of a feedback bias network for a transistor. Nah, it just proves that taking things out of context comes too easily for you. Recall that in Post#74 you...
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    Transistors / hfe / Active region conflicts

    The base current Ib is controlled by the collector current in this feedback scheme. The collector current flows through the emitter resistor to develop the emitter voltage. The emitter voltage plus one diode drop (Vbe) subtracted from the Thevenin equivalent bias voltage, divided by the...
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    Transistors / hfe / Active region conflicts

    Don't be so quick to dismiss empirical methods. If the theoretical prediction did not agree with the empirical result, then the physicists would need to develop a better theory. The empirical result is definitive.
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    Transistors / hfe / Active region conflicts

    Not really. I just have to look up the I-V characteristic curve for the diode.
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    Transistors / hfe / Active region conflicts

    Biasing with a stiff base voltage is done with emitter feedback for Ib which makes the value of junction voltage not relevant. I'm not inclined to repeat that explanation again.
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