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  1. R

    How a BJT Transistor works (base current version)

    Not in a BJT anyway. But it can do so in a magnetic amplifier (MA). An MA is constructed somewhat like a transformer, only it has an easily saturable core. A small amount of current in the input coil can saturate the core to whatever level is desired. If the core is completely saturated, the...
  2. R

    How a BJT Transistor works (base current version)

    Plots do not prove your assertion of what is in control. There can be phase differences between the inputs and outputs that confuse sequential analysis. Plots only tell you what happened, not what caused it to happen. Equations do not tell you how things work, either. Equations only tell you...
  3. R

    Differential amplifier single ended output calculations

    Your calculations look good to me. The collector circuits should act like current sources, so a little resistance in the collector should not change the current too much. I would probe and compare the emitter currents of both transistors and also vbe and Vc and see if they correlate with the...
  4. R

    How a BJT Transistor works (base current version)

    You aver that a BJT must be current driven. Not quite true. A BJT must be current limited, like just about any electronic device (anybody say resistor?) Anyway, a BJT is still a transconductance device. That means that in the active region, the vbe will control the Ic. You can observe that...
  5. R

    How a BJT Transistor works (base current version)

    To the Ineffable All, The BJT technology is old and mature. A lot is known about how BJTs work. Everything should be referenced by the physics of the device, and not the circuit in which they are used. A lot of the previous discussion is concerned with what happens first. That is like...
  6. R

    Power through current sources

    I don't know how the rest of this group interprets the diagram, but I go by what a voltmeter and ammeter would indicate. Ratch
  7. R

    Power through current sources

    Yes, the answer key is wrong. The 4 ma source absorbs 8 mw and the 2 ma source supplies 20 mw. Ratch
  8. R

    RL Circuit

    The answer you give above is not the same as your worksheet answer. Why is there an undefined constant in your answer? Ratch
  9. R

    Different answer using inverting op-amp and KCL?

    Here is an analysis using only the node method. The node "vb" is the minus terminal of the op-amp. The term "amp" represents the finite amplification factor of the op-amp. In the solution, setting "amp" to infinity gives the same answer as before. Ratch
  10. R

    Different answer using inverting op-amp and KCL?

    The solution I gave does not take into consideration whether it is an inverting amp or not. The second equation in the solution I submitted is a loop equation, and gives vo = -4.5 . Compare your loop equation with mine, and see where the difference lies. Ratch
  11. R

    Different answer using inverting op-amp and KCL?

    I have a bit of an interesting problem (see attachment), I've calculated V_a in the first part of the question. Then I've applied KCL at the ground node to try and solve for V_0. I know that V_0 should be -4.5V due to the inverting op-amp being present but KCL gives me 4.5V? Thank you! You...
  12. R

    Voltage Divider +12V, -12V, Ground.

    It was an oversight on my part for not recognizing earlier that this circuit is a easy application of Millman's theorem. ((-12/20000)+(12/543))*(543||20000||1837) = 8.82577 volts Ratch
  13. R

    Voltage Divider +12V, -12V, Ground.

    OK, we have two voltages +12, and -12 that are going to supply current to the circuit. Because it is a linear circuit, the total current will be the total contribution of both voltages taken separately. If we find the total current in the R3, R4 branch, then it will be a trivial task to...
  14. R

    Voltage Divider +12V, -12V, Ground.

    No need to redraw the diagram. Just ignore the voltage meters. The circuit topology is two loops or one node. I will calculate the loop currents first. The first loop is -12, R2,R1,-12 and the second loop is R4,R3,R2,+12 . Each loop needs an equation, and they are (20000+543)*i1-20000*i2=24...
  15. R

    Voltage Divider +12V, -12V, Ground.

    Call me stupid or call me dense, but I don't understand the problem. I calculated all the voltages using 2 loops and they are all correct. The voltage across R3 and R4 are 8.03 volts like the schemat says they are, so what is the problem? Ratch
  16. R

    Noob Question About Current From Voltage Regulators

    Hmm, maybe we should start again. The 2 amp specification of your voltage source simply means that it is capable of supplying up to 2 amps of current at whatever voltage it is set at. If your circuit draws more than 2 amps, the voltage source will probably blow its fuse. Any questions about...
  17. R

    stuck between the problem

    What book are you using? Doesn't it have the formula shown in the attachment? When Nv and Nc are multiplied together, the "2" in the denominator is cancelled and "3" remains. Ratch
  18. R

    stuck between the problem

    Nv and Nc have their temperature parameters inside a term raised to the 3/2 power. You don't need to take those temperatures outside the radical, but if you do, you have to compensate for their removal. The solution seems to have elected to move the temperature parameter to the outside the...
  19. R

    stuck between the problem

    Nc and Nv have temperature parameters that are raised to the 3/2 power. If the temperature ratios are moved outside the exponent brackets, then the temperature ratios have to be raised to the third power to compensate for the move. Ratch
  20. R

    fermi level

    They are talking about the Fermi function, which uses the Fermi level as one of its parameters. You have stated that you clearly know what the Fermi level is. The Fermi function is a probability distribution function of how many of the existing states will be filled with an electron. The...
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